LIFE TECHNOLOGIES INC
SC 14D1/A, 1998-12-07
BIOLOGICAL PRODUCTS, (NO DIAGNOSTIC SUBSTANCES)
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<PAGE>   1
==============================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                ----------------

                                 SCHEDULE 14D-1
                             TENDER OFFER STATEMENT
      (PURSUANT TO SECTION 14(D)(1) OF THE SECURITIES EXCHANGE ACT OF 1934)
                                (AMENDMENT NO. 5)

                             LIFE TECHNOLOGIES, INC.
                            (NAME OF SUBJECT COMPANY)

                               DEXTER CORPORATION
                        DEXTER ACQUISITION DELAWARE, INC.
                                    (BIDDERS)

                     COMMON STOCK, PAR VALUE $.01 PER SHARE
                         (TITLE OF CLASS OF SECURITIES)

                                    532177201
                      (CUSIP NUMBER OF CLASS OF SECURITIES)

                                ----------------

                              BRUCE H. BEATT, ESQ.
                  VICE PRESIDENT, GENERAL COUNSEL AND SECRETARY
                               DEXTER CORPORATION
                                 ONE ELM STREET
                             WINDSOR LOCKS, CT 06096
                                 (860) 292-7675
            (NAME, ADDRESS AND TELEPHONE NUMBER OF PERSON AUTHORIZED
           TO RECEIVE NOTICES AND COMMUNICATIONS ON BEHALF OF BIDDERS)

                                ----------------

                                    COPY TO:
                              JERE R. THOMSON, ESQ.
                           JONES, DAY, REAVIS & POGUE
                              599 LEXINGTON AVENUE
                            NEW YORK, NEW YORK 10022
                                 (212) 326-3939


                           CALCULATION OF FILING FEE:


================================================================================
       TRANSACTION VALUATION*                             AMOUNT OF FILING FEE**
- --------------------------------------------------------------------------------

         $498,201,474                                          $99,640       

================================================================================

 *       For purposes of calculating the amount of filing fee only. The amount
         assumes the purchase of 12,733,584 shares of Common Stock, par value 
         



<PAGE>   2




         $.01 per share, of Life Technologies, Inc. at $39.125 net per share in
         cash which represents all outstanding shares at October 29, 1998 not
         owned by the persons filing this statement and shares issuable pursuant
         to options that are presently exercisable.

**       The amount of the filing fee calculated in accordance with Regulation
         240.0-11 of the Securities Exchange Act of 1934 equals 1/50th of 1% of
         the value of the shares to be purchased.

[X]      Check box if any part of the fee is offset as provided by Rule
         0-11(a)(2) and identify the filing with which the offsetting fee was
         previously paid. Identify the previous filing by registration statement
         number, or the Form or Schedule and the date of its filing.



Amount Previously Paid:     $92,306         Filing Party: Dexter Corporation
                                                          and Dexter Acquisition
                                                          Delaware, Inc.

Form or Registration No.:   Schedule 14D-1  Date Filed:   November 2, 1998

================================================================================



<PAGE>   3






         Dexter Acquisition Delaware, Inc., a Delaware corporation ("Purchaser")
and a wholly-owned subsidiary of Dexter Corporation, a Connecticut corporation
("Parent"), and Parent hereby amend and supplement their Tender Offer Statement
on Schedule 14D-1 filed with the Securities and Exchange Commission (the
"Commission") on November 2, 1998, as amended by Amendments No. 1, No. 2, No. 3
and No. 4 thereto filed with the Commission on November 5, 1998, November 12,
1998, November 23, 1998 and December 2, 1998, respectively (as so amended, the
"Schedule 14D-1"). Capitalized terms not defined herein have the meaning
ascribed to them in the Schedule 14D-1.

ITEM 1. SECURITY AND SUBJECT COMPANY.

  (b) Item 1(b) of the Schedule 14D-1 is hereby amended and supplemented to
incorporate by reference the information set forth in the sections entitled
"INTRODUCTION," "SPECIAL FACTORS--Background of the Offer" and "THE AMENDED
OFFER--Amended Terms of the Offer" of the Supplement, dated December 7, 1998
(the "Supplement"), to the Offer to Purchase, dated November 2, 1998.

  (c) Item 1(c) of the Schedule 14D-1 is hereby amended and supplemented to
incorporate by reference the information set forth in the section entitled "THE
AMENDED OFFER--Price Range of Shares; Dividends" of the Supplement.

ITEM 3. PAST CONTACTS, TRANSACTIONS OR NEGOTIATIONS WITH THE SUBJECT COMPANY.

  (b) Item 3(b) of the Schedule 14D-1 is hereby amended and supplemented to
incorporate by reference the information set forth in the sections entitled
"INTRODUCTION" and "SPECIAL FACTORS--Background of the Offer" of the Supplement.

ITEM 4. SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION.

  (a)-(b) Items 4(a)-(b) of the Schedule 14D-1 are hereby amended and
supplemented to incorporate by reference the information set forth in the
section entitled "THE AMENDED OFFER--Source and Amount of Funds" of the
Supplement.

ITEM 5. PURPOSE OF THE TENDER OFFER AND PLANS OR PROPOSALS OF THE BIDDER.

  (a)-(g) Items 5(a)-(g) of the Schedule 14D-1 are hereby amended and 
supplemented to incorporate by reference the information set forth in the 
sections entitled "INTRODUCTION," "SPECIAL FACTORS--Purpose and Structure of 
the Offer; Plans for the Company after the Offer" and "THE AMENDED OFFER--
Certain Effects of the Transaction" of the Supplement.

ITEM 10. ADDITIONAL INFORMATION.

  (e) Item 10(e) of the Schedule 14D-1 is hereby amended and supplemented to
incorporate by reference the information set forth in the section entitled
"SPECIAL FACTORS--Background of the Offer" of the Supplement.

  (f) Item 10(f) of the Schedule 14D-1 is hereby amended and supplemented to
incorporate by reference the information set forth in the entire Supplement and
the revised Letter of Transmittal, copies of which are filed herewith as
exhibits (a)(11) and (a)(12), respectively.

ITEM 11. MATERIAL TO BE FILED AS EXHIBITS.

  Item 11 of the Schedule 14D-1 is hereby amended and supplemented to add the
following exhibits:

  (a)(11) Supplement to the Offer to Purchase.

  (a)(12) Revised Letter of Transmittal.

  (a)(13) Revised Notice of Guaranteed Delivery.




<PAGE>   4




  (a)(14) Text of press release issued by Parent, dated December 7, 1998.

  (b)(2) Letter to Parent, dated December 5, 1998, amending the Term Sheet
delivered by The First National Bank of Chicago.


<PAGE>   5






                                   SIGNATURE

  AFTER DUE INQUIRY AND TO THE BEST OF MY KNOWLEDGE AND BELIEF, I CERTIFY THAT
THE INFORMATION SET FORTH IN THIS STATEMENT IS TRUE, COMPLETE AND CORRECT.



Dated: December 7, 1998                   DEXTER ACQUISITION DELAWARE, INC.

                                          By:  /s/ Kathleen Burdett
                                               ------------------------------
                                               Name:    Kathleen Burdett
                                               Title:   Treasurer



                                          DEXTER CORPORATION

                                          By:  /s/ Bruce H. Beatt
                                               ------------------------------
                                               Name:    Bruce H. Beatt
                                               Title:   Vice President, General
                                                        Counsel and Secretary


<PAGE>   6




                                    EXHIBIT INDEX



 EXHIBIT
 NUMBER                              DESCRIPTION
 -------                             -----------

(a)(11)         Supplement to the Offer to Purchase.

(a)(12)         Revised Letter of Transmittal.

(a)(13)         Revised Notice of Guaranteed Delivery.

(a)(14)         Text of press release issued by Parent, dated December 7, 1998.

(b)(2)          Letter to Parent, dated December 5, 1998, amending the Term
                Sheet delivered by The First National Bank of Chicago.


<PAGE>   1
 
           SUPPLEMENT TO THE OFFER TO PURCHASE DATED NOVEMBER 2, 1998
 
                       DEXTER ACQUISITION DELAWARE, INC.
                          A WHOLLY-OWNED SUBSIDIARY OF
 
                               DEXTER CORPORATION
                          IS NOW OFFERING TO PURCHASE
               ANY AND ALL OUTSTANDING SHARES OF COMMON STOCK OF
 
                            LIFE TECHNOLOGIES, INC.
                      AND HAS INCREASED THE OFFER PRICE TO
 
                         $39.125 NET PER SHARE IN CASH
 
    THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK
    CITY TIME, ON TUESDAY, DECEMBER 22, 1998, UNLESS THE OFFER IS EXTENDED.
 
     This Supplement amends and supplements the Offer to Purchase, dated
November 2, 1998, as amended (the "November 2 Offer to Purchase"), relating to
the Offer by Dexter Acquisition Delaware, Inc. ("Purchaser"), a wholly-owned
subsidiary of Dexter Corporation ("Parent"), to purchase any and all outstanding
shares of common stock, par value $.01 per share ("Shares"), of Life
Technologies, Inc. (the "Company") not owned by Parent (the "Publicly-held
Shares"). Purchaser hereby offers to purchase any and all Publicly-held Shares
at a purchase price of $39.125 per share, net to the seller in cash, without
interest thereon, upon the terms and subject to the conditions set forth in the
November 2 Offer to Purchase, this Supplement and in the revised Letter of
Transmittal.
 
     THE MINIMUM SHARE CONDITION TO THE OFFER SET FORTH IN THE NOVEMBER 2 OFFER
TO PURCHASE HAS BEEN ELIMINATED AND THE OFFER IS NO LONGER CONDITIONED UPON ANY
MINIMUM NUMBER OF SHARES BEING VALIDLY TENDERED AND NOT WITHDRAWN PRIOR TO THE
EXPIRATION DATE. THE OFFER, HOWEVER, REMAINS SUBJECT TO CERTAIN OTHER
CONDITIONS. SEE "THE AMENDED OFFER -- AMENDED CONDITIONS OF THE OFFER".
 
     THE OFFER IS NOT CONDITIONED ON THE AVAILABILITY OF FINANCING OR ON THE
APPROVAL OF THE BOARD OF DIRECTORS OF THE COMPANY OR ANY COMMITTEE THEREOF.
 
     PARENT CURRENTLY BENEFICIALLY OWNS 12,246,664 SHARES, REPRESENTING
APPROXIMATELY 51.5% OF THE OUTSTANDING SHARES AT OCTOBER 29, 1998.
 
     PURCHASER DOES NOT INTEND TO FURTHER EXTEND OR AMEND THE OFFER.
 
     THIS TRANSACTION HAS NOT BEEN APPROVED OR DISAPPROVED BY THE UNITED STATES
SECURITIES AND EXCHANGE COMMISSION (THE "COMMISSION") NOR HAS THE COMMISSION
PASSED UPON THE FAIRNESS OR MERITS OF SUCH TRANSACTION NOR UPON THE ACCURACY OR
ADEQUACY OF THE INFORMATION CONTAINED IN THIS DOCUMENT. ANY REPRESENTATION TO
THE CONTRARY IS UNLAWFUL.
 
                            ------------------------
 
                      The Dealer Manager for the Offer is:
 
                              MERRILL LYNCH & CO.
December 7, 1998
<PAGE>   2
 
                                   IMPORTANT
 
     Any stockholder desiring to tender all or a portion of such stockholder's
Shares should either (a)(i) complete and sign the revised Letter of Transmittal
or a facsimile thereof in accordance with the instructions in the revised Letter
of Transmittal, have such stockholder's signature thereon guaranteed if required
by Instruction 1 to the revised Letter of Transmittal and mail or deliver the
revised Letter of Transmittal together with the certificate(s) representing
tendered Shares and all other required documents to the Depositary, or (ii)
tender such Shares pursuant to the procedure for book-entry transfer set forth
in "THE TENDER OFFER -- Procedure for Tendering Shares" or (b) request such
stockholder's broker, dealer, commercial bank, trust company or other nominee to
effect the transaction for such stockholder. Stockholders having Shares
registered in the name of a broker, dealer, commercial bank, trust company or
other nominee must contact such person if they desire to tender their Shares.
Any stockholder who desires to tender Shares and whose certificates representing
such Shares are not immediately available, or who cannot comply with the
procedures for book-entry transfer on a timely basis, may tender such Shares
pursuant to the guaranteed delivery procedure set forth in "THE TENDER
OFFER -- Procedure for Tendering Shares" and "THE AMENDED OFFER -- Procedure for
Tendering Shares" herein.
 
     STOCKHOLDERS WHO PREVIOUSLY TENDERED THEIR SHARES PURSUANT TO THE OFFER ARE
NOT REQUIRED TO TAKE ANY FURTHER ACTION IN ORDER TO RECEIVE THE INCREASED PRICE
OF $39.125 PER SHARE, EXCEPT AS MAY BE REQUIRED BY THE PROCEDURE FOR GUARANTEED
DELIVERY IF SUCH PROCEDURE WAS UTILIZED.
 
     TENDERING STOCKHOLDERS OTHERWISE ENTITLED THERETO WILL RECEIVE THE
COMPANY'S DIVIDEND OF $.05 PER SHARE PAYABLE ON JANUARY 15, 1999 TO ALL
STOCKHOLDERS OF RECORD ON DECEMBER 18, 1998 WHICH WAS DECLARED ON NOVEMBER 10,
1998.
 
     TENDERING STOCKHOLDERS MAY CONTINUE TO USE THE ORIGINAL BLUE LETTER OF
TRANSMITTAL AND THE ORIGINAL PINK NOTICE OF GUARANTEED DELIVERY PREVIOUSLY
CIRCULATED WITH THE OFFER TO PURCHASE OR MAY USE THE REVISED GRAY LETTER OF
TRANSMITTAL AND THE REVISED SALMON NOTICE OF GUARANTEED DELIVERY CIRCULATED WITH
THIS SUPPLEMENT.
 
     Questions and requests for assistance may be directed to the Information
Agent or to the Dealer Manager at their respective addresses and telephone
numbers set forth on the back cover of this Supplement. Additional copies of
this Supplement, the revised Letter of Transmittal, the revised Notice of
Guaranteed Delivery and other related materials may be obtained from the
Information Agent or from brokers, dealers, commercial banks and trust
companies.
<PAGE>   3
 
                               TABLE OF CONTENTS
 
<TABLE>
<CAPTION>
                                                              PAGE
                                                              ----
<S>                                                           <C>
INTRODUCTION................................................    1
SPECIAL FACTORS.............................................    3
  Background of the Offer...................................    3
  Fairness of the Offer.....................................    5
  Purpose and Structure of the Offer; Plans for the Company
     after the Offer........................................    5
THE AMENDED OFFER...........................................    6
  Amended Terms of the Offer................................    6
  Procedure for Tendering Shares............................    6
  Certain Information Concerning the Company................    7
  Price Range of Shares; Dividends..........................    8
  Certain Effects of the Transaction........................    8
  Source and Amount of Funds................................    9
  Amended Conditions of the Offer...........................   10
  Miscellaneous.............................................   13
</TABLE>
<PAGE>   4
 
To the Holders of Common Stock of Life Technologies, Inc.:
 
                                  INTRODUCTION
 
     The following information amends and supplements the Offer to Purchase,
dated November 2, 1998, as amended by Amendments No. 1, 2, 3 and 4 to the Tender
Offer Statement on Schedule 14D-1 filed with the Securities and Exchange
Commission (the "Commission") on November 5, 1998, November 12, 1998, November
23, 1998 and December 2, 1998, respectively (as so amended, the "November 2
Offer to Purchase", and together with this Supplement, the "Offer to Purchase"),
of Dexter Acquisition Delaware, Inc., a Delaware corporation ("Purchaser") and a
wholly-owned subsidiary of Dexter Corporation, a Connecticut corporation
("Parent"). Purchaser hereby offers to purchase any and all outstanding shares
of common stock, par value $.01 per share of Life Technologies, Inc. (the
"Company") not owned by Parent (the "Publicly-held Shares") at a purchase price
of $39.125 per share (the "Revised Offer Price"), net to the seller in cash,
without interest thereon, upon the terms and subject to the conditions set forth
in the Offer to Purchase and the related revised Letter of Transmittal which, as
further amended and supplemented from time to time, constitute the "Offer."
 
     Except as otherwise set forth in this Supplement and the revised Letter of
Transmittal, the terms and conditions previously set forth in the November 2
Offer to Purchase and the related Letter of Transmittal remain applicable in all
respects to the Offer, and this Supplement should be read in conjunction with
the November 2 Offer to Purchase. Capitalized terms used and not otherwise
defined herein have the meaning ascribed to them in the November 2 Offer to
Purchase. Procedures for tendering Shares are set forth in the sections entitled
"THE TENDER OFFER -- Procedure for Tendering Shares" of the November 2 Offer to
Purchase and "THE AMENDED OFFER -- Procedure for Tendering Shares" herein.
 
     THE MINIMUM CONDITION TO THE OFFER SET FORTH IN THE NOVEMBER 2 OFFER TO
PURCHASE HAS BEEN WAIVED AND THE OFFER IS NO LONGER CONDITIONED UPON ANY MINIMUM
NUMBER OF SHARES BEING VALIDLY TENDERED AND NOT WITHDRAWN PRIOR TO THE
EXPIRATION DATE. THE OFFER, HOWEVER, REMAINS SUBJECT TO CERTAIN OTHER
CONDITIONS. SEE "THE AMENDED OFFER -- AMENDED CONDITIONS OF THE OFFER".
 
     THE OFFER TO PURCHASE AND THE REVISED LETTER OF TRANSMITTAL CONTAIN
IMPORTANT INFORMATION WHICH SHOULD BE READ BEFORE ANY DECISION IS MADE WITH
RESPECT TO THE OFFER.
 
     The fifth paragraph of the section entitled "Introduction" of the November
2 Offer to Purchase is hereby amended by amending and restating it in its
entirety as follows:
 
          Parent and Purchaser currently desire, following the consummation of
     the Offer, to have the Company effect a merger (the "Second Step Merger")
     in accordance with the relevant provisions of the General Corporation Law
     of the State of Delaware (the "DGCL") in which Purchaser will be merged
     with and into the Company. At the effective time of the Second Step Merger
     (the "Effective Time"), each Share not tendered pursuant to the Offer
     (other than Shares owned by the Company as treasury stock, Shares owned by
     Parent or Purchaser or any subsidiary thereof, or Shares with respect to
     which appraisal rights are properly exercised under Delaware law) would be
     converted into the right to receive an amount in cash equal to the Revised
     Offer Price (the "Merger Consideration"). Following consummation of the
     Second Step Merger, the Company would continue as the surviving corporation
     (the "Surviving Corporation") and would be a wholly-owned subsidiary of
     Parent.
 
     The seventh paragraph of the section entitled "Introduction" of the
November 2 Offer to Purchase is hereby amended by amending and restating it in
its entirety as three full paragraphs as follows:
 
          If a "short form" merger cannot be effectuated because Parent and
     Purchaser own less than 90% of the outstanding Shares following
     consummation of the Offer, consummation of the Second Step Merger would
     require the approval by the Company Board of an agreement between the
     Company, Parent and
<PAGE>   5
 
     Purchaser with respect to the Second Step Merger (a "Merger Agreement") and
     the adoption of a Merger Agreement by the holders of at least 80% of the
     outstanding Shares (including Parent and Purchaser, who would vote all
     Shares owned by them for such approval). Accordingly, if Parent and
     Purchaser own more than 80% of the outstanding Shares, they would have the
     power to cause the adoption of a Merger Agreement without the affirmative
     vote of any other stockholder.
 
          If Parent and Purchaser own 80% or more but less than 90% of the
     outstanding Shares following consummation of the Offer, Parent and
     Purchaser currently intend to promptly use their best efforts to take such
     steps as are necessary to cause the Second Step Merger to be effective
     pursuant to a Merger Agreement, including voting the Shares owned by them
     for adoption of the Merger Agreement which will, if the Shares remain
     registered under the Securities Exchange Act of 1934, as amended (the
     "Exchange Act"), require filing with the Commission of certain disclosure
     materials prior to adoption of the Second Step Merger by the Company's
     stockholders.
 
          If Parent and Purchaser own less than 80% of the outstanding Shares
     following consummation of the Offer, they may either seek to proceed with
     the Second Step Merger as described in the preceding paragraph or for an
     indeterminate period, delay the Second Step Merger and engage in certain
     open market or privately negotiated purchases, at prices which may be
     greater or less than the Revised Offer Price, in order to increase Parent
     and Purchaser's combined ownership of Shares. The timing and amount of, and
     prices paid for, such purchases would depend upon the number of Shares then
     held by Parent and Purchaser, the identity and intentions of the Company's
     other stockholders, prevailing market prices for the Shares, developments
     affecting the Company and other factors which cannot be predicted at this
     time. See "THE TENDER OFFER -- Certain Effects of the Transaction". As a
     consequence, no assurance can be given as to whether or when Purchaser will
     cause the Second Step Merger to be consummated. In addition, no assurance
     can be given as to whether or when the Merger Consideration will be paid to
     stockholders who do not tender their Shares in the Offer. IN NO EVENT WILL
     ANY INTEREST BE PAID ON THE MERGER CONSIDERATION. See "SPECIAL FACTORS --
     Purpose and Structure of the Offer; Plans for the Company after the Offer".
 
                                        2
<PAGE>   6
 
                                SPECIAL FACTORS
 
BACKGROUND OF THE OFFER
 
     The Purchaser previously amended and supplemented the discussion set forth
under the section entitled "SPECIAL FACTORS -- Background of the Offer" of the
November 2 Offer to Purchase in Amendment No. 3 to the Schedule 14D-1 filed with
the Commission on November 23, 1998, as follows:
 
          (a) The first full paragraph below replaces the third full paragraph
     under "SPECIAL FACTORS -- Background of the Offer" and the second full
     paragraph below was added as the new fourth paragraph under "SPECIAL
     FACTORS -- Background of the Offer":
 
             In 1998, as part of a strategic review of Parent's entire business,
        Parent's management evaluated its investment in the Company. In this
        regard, Merrill Lynch was engaged to provide Parent with financial
        advisory and investment banking services in accordance with an
        engagement letter dated May 1, 1998. The results of this strategic
        review were presented to Parent's Board of Directors (the "Parent
        Board") at an informal meeting held on June 23, 1998 and at a regular
        meeting held on June 24, 1998, including management's recommendation
        that Parent seek to acquire all of the Company's equity interest which
        Parent did not then own. The Parent Board concluded that, if such
        acquisition were to be sought and completed, it would be desirable for
        J. Stark Thompson, Ph.D., the chief executive officer of the Company, to
        continue in that capacity.
 
             The presentation of Merrill Lynch at such meetings (the "June
        Presentation") was based solely on publicly-available information and
        estimates of future financial results published by First Call
        Corporation and selected brokerage firms and was used to assist Parent
        in determining the appropriate price for the Proposal. Such presentation
        analyzed the pro forma effect on Parent of a transaction involving a
        hypothetical offer price of $38.00 per share and a sensitivity analysis
        of plus or minus $1.00 per share (the "Hypothetical Range"). The
        presentation also included analyses similar to those analyses described
        below under "-- Analysis of Financial Advisor to Parent-Analyses of
        Selected Comparable Publicly Traded Companies" and "-- Analysis of
        Change of Control Acquisitions". For purposes of comparing implied
        multiples, Merrill Lynch used the mid-point of the Hypothetical Range,
        which represented a premium of 19.2% over the Company's closing price on
        NASDAQ (as defined below) of $31.88 per share on June 22, 1998. The full
        text of the June Presentation has been included as Exhibit (g)(6) to the
        Schedule 13E-3 and the Schedule 14D-1 and the foregoing summary is
        qualified in its entirety by reference to such Exhibit. See the last
        five paragraphs under "-- Analysis of Financial Advisor to Parent" for
        qualifying statements as to the October 23, 1998 presentation of Merrill
        Lynch which qualifying statements apply to its June Presentation as
        well, including as to any projections included therein.
 
          (b) The fifth paragraph under "SPECIAL FACTORS -- Background of the
     Offer" was amended by amending and restating it in its entirety as follows:
 
             On July 6, 1998, in a special meeting of the Parent Board, the
        Parent Board authorized Mr. Walker to make a proposal on behalf of
        Parent to acquire all of the shares of the Company not currently owned
        by Parent for $37.00 in cash. Such price represented a premium of 20.1%
        over the Company's closing price on NASDAQ of $30.81 per share on July
        2, 1998.
 
          (c) The twenty-sixth paragraph under "SPECIAL FACTORS -- Background of
     the Offer" was amended by amending and restating it in its entirety as
     follows:
 
             On October 14, 1998, the Parent Board held a special telephonic
        meeting to receive reports on the Proposal from Parent's management and
        its financial advisor on the Special Committee's response to the
        Proposal and related matters. The presentation of Merrill Lynch set
        forth in its October 14, 1998 presentation contained analyses similar to
        those set forth in its October 23, 1998 presentation and described under
        "-- Analyses of Financial Advisor to Parent". Such presentation also
        analyzed the pro forma impact of the transaction on Parent. All such
        analyses used the Offer Price. The full text of Merrill Lynch's written
        presentation delivered to the Parent Board on October 14, 1998 has been
        included as Exhibit (g)(7) to the Schedule 13E-3 and the Schedule 14D-1
        and
                                        3
<PAGE>   7
 
        the foregoing summary is qualified in its entirety by reference to such
        Exhibit. See the last five paragraphs under "-- Analysis of Financial
        Advisor to Parent" for qualifying statements as to the October 23, 1998
        presentation of Merrill Lynch which qualifying statements apply to its
        October 14, 1998 presentation as well, including as to any projections
        included therein.
 
          (d) The second sentence contained in the twenty-ninth paragraph under
     "SPECIAL FACTORS -- Background of the Offer" was amended by amending and
     restating such second sentence in its entirety as set forth below:
 
             On October 23, 1998, at a regular meeting of the Parent Board,
        Parent's management and representatives of Parent's financial advisors
        and legal counsel reviewed with the Parent Board the status and fairness
        of the Proposal. See "Certain Factors -- Fairness of the Offer" and
        "-- Analysis of Financial Advisor to Parent". Mr. Walker advised the
        Parent Board that he had convened a special telephonic meeting of the
        Company Board for Tuesday, October 27, 1998, to receive a report on the
        status of the Special Committee's review of the Proposal from the
        Special Committee. The Parent Board authorized Mr. Walker to withdraw
        the Proposal if he believed that to be in Parent's best interest; the
        Parent Board also authorized Parent to proceed with the Offer if the
        Proposal was withdrawn.
 
     The following paragraphs are added after the last full paragraph under
"SPECIAL FACTORS -- Background of the Offer":
 
          On November 4, 1998 the Company issued a press release announcing that
     Messrs. Samuel and Wylie resigned as members of the Company Board effective
     November 3, 1998. In their letters of resignation and a Joint Statement of
     the Former Members of the Special Committee of Independent Directors of
     Life Technologies, Inc. (the "Joint Statement") (which were filed as
     Exhibits 17.1 and 17.2 to the Company's Current Report on Form 8-K, dated
     November 6, 1998), Messrs. Samuel and Wylie cited their disagreement with
     certain actions taken by the Company Board in connection with the Offer
     (including the decision to disband the Special Committee) and the reasons
     why they opposed the Proposal.
 
          On November 8, 1998, the Company issued a press release announcing
     that on November 6, 1998, an Amended and Consolidated Class Action
     Complaint and Motion for Preliminary Injunction (the "Motion") had been
     filed in the Court of Chancery of the State of Delaware in the action
     entitled In Re Life Technologies, Inc. Shareholders Litigation
     (Consolidated Civil Action No. 16513). The Company indicated in the press
     release that the amended complaint alleged, among other things, that Parent
     and the defendant directors of the Company who are affiliated with Parent
     had breached or may breach their respective fiduciary duties to the
     Company's public shareholders and sought to enjoin the defendants from
     consummating the Offer and sought monetary damages and costs. The Delaware
     Chancery Court denied the Motion on November 24, 1998.
 
          On November 16, 1998, the Company filed the Schedule 14D-9
     Solicitation/Recommendation Statement (the "Schedule 14D-9")which disclosed
     that the Company Board determined that the Company would express no opinion
     and would remain neutral with respect to the Offer because a majority of
     the Company Board is affiliated with Parent. The Company included in the
     Schedule 14D-9 the view of Dr. Adams that the shareholders should reject
     the Offer and not tender their Shares. The Schedule 14D-9 contains other
     information requested to be included by Dr. Adams, including without
     limitation the Joint Statement and "Analysis of Goldman Sachs," which
     summarizes certain analyses provided by Goldman Sachs to the Special
     Committee. The reasons given by Dr. Adams (set forth in the Joint
     Statement) included that the Offer omitted or ignored significant
     components to the Company's long-term inherent value and earning power,
     including the R&D Pipeline.
 
          On December 2, 1998 Parent issued a press release announcing the
     extension of the original Offer until 12:00 midnight, New York City time,
     on Friday, December 4, 1998 and that, based on information provided by the
     Depositary, as of 12:00 midnight on Tuesday, December 1, 1998,
     approximately 2,337,440 Publicly-held Shares had been tendered and not
     withdrawn. According to information provided
 
                                        4
<PAGE>   8
 
     by the Depositary, as of 12:00 midnight, New York City time, on Friday,
     December 4, 1998, approximately 2,255,412 Publicly-held Shares had been
     tendered and not withdrawn.
 
FAIRNESS OF THE OFFER
 
     The discussion set forth in the section entitled "SPECIAL
FACTORS -- Fairness of the Offer" of the November 2 Offer to Purchase is hereby
amended and supplemented by the addition of the following paragraph as the third
paragraph under such section:
 
          As noted above, following the Pre-Announcement Date, various stock
     market indices declined significantly. Since the preparation of the Merrill
     Lynch analysis presented to the Parent Board on October 23, 1998 and the
     commencement of the Offer on November 2, 1998, however, such indices have
     risen to levels which, in general, are consistent with their levels on the
     Pre-Announcement Date. Such market increases have not caused Parent to
     change its belief that the original Offer Price of $37.00 per Share remains
     fair. Parent also believes that the Revised Offer Price is fair. Since
     October 23, 1998 Merrill Lynch has not been requested to present to Parent
     any valuation analyses with respect to the Company and has not presented
     any such analyses.
 
PURPOSE AND STRUCTURE OF THE OFFER; PLANS FOR THE COMPANY AFTER THE OFFER
 
     The fourth paragraph of the section entitled "SPECIAL FACTORS -- Purpose
and Structure of the Offer; Plans for the Company after the Offer" of the
November 2 Offer to Purchase is hereby amended by amending and restating it in
its entirety as follows:
 
          Parent and Purchaser currently desire, following the consummation of
     the Offer, to have the Company consummate the Second Step Merger. In such
     event, in accordance with the relevant provisions of the DGCL, Purchaser
     would be merged with and into the Company. The purpose of the Second Step
     Merger would be to acquire all Publicly-held Shares not tendered and
     purchased pursuant to the Offer or otherwise held by Purchaser or Parent.
     In the Second Step Merger, each then-outstanding Share (other than Shares
     owned by the Company as treasury stock, Shares owned by Parent or
     Purchaser, or Shares with respect to which appraisal rights are properly
     exercised under Delaware law) would be converted into the right to receive
     the Merger Consideration. See "SPECIAL FACTORS -- Appraisal Rights in the
     Merger." Following consummation of the Second Step Merger, the Company
     would continue as the Surviving Corporation and be a wholly-owned
     subsidiary of Parent.
 
     The sixth paragraph of the section entitled "SPECIAL FACTORS -- Purpose and
Structure of the Offer; Plans for the Company after the Offer" of the November 2
Offer to Purchase is hereby amended by amending and restating it in its entirety
as three full paragraphs as follows:
 
          If a "short form" merger cannot be effectuated because Parent and
     Purchaser own less than 90% of the outstanding Shares following
     consummation of the Offer, consummation of the Second Step Merger would
     require the approval by the Company Board of a Merger Agreement and the
     adoption of a Merger Agreement by the holders of at least 80% of the
     outstanding Shares (including Parent and Purchaser, who would vote all
     Shares owned by them for such approval). Accordingly, if Parent and
     Purchaser own more than 80% of the outstanding Shares, they would have the
     power to cause the adoption of a Merger Agreement without the affirmative
     vote of any other stockholder.
 
          If Parent and Purchaser own 80% or more but less than 90% of the
     outstanding Shares following consummation of the Offer, Parent and
     Purchaser currently intend to promptly use their best efforts to take such
     steps as are necessary to cause the Second Step Merger to be effective
     pursuant to a Merger Agreement, including voting the Shares owned by them
     for adoption of a Merger Agreement which will, if the Shares remain
     registered under the Exchange Act, require filing with the Commission of
     certain disclosure materials prior to adoption of the Second Step Merger by
     the Company's stockholders.
 
          If Parent and Purchaser own less than 80% of the outstanding Shares
     following consummation of the Offer, they may either seek to proceed with
     the Second Step Merger as described in the preceding paragraph or for an
     indeterminate period, delay the Second Step Merger and engage in certain
     open
                                        5
<PAGE>   9
 
     market or privately negotiated purchases, at prices which may be greater or
     less than the Revised Offer Price, in order to increase Parent and
     Purchaser's combined ownership of Shares. Any such acquisition of Shares by
     Purchaser would have to be made in accordance with applicable legal
     requirements, including those of Regulation 13D and Rules 10b-18 and 13e-3
     under the Exchange Act. See "THE TENDER OFFER -- Certain Effects of the
     Transaction." The timing and amount of, and prices paid for, such purchases
     would depend upon the number of Shares then held by Parent and Purchaser,
     the identity and intentions of the Company's other stockholders, prevailing
     market prices for the Shares, developments affecting the Company and other
     factors which cannot be predicted at this time. As a consequence, no
     assurance can be given as to whether or when Purchaser will cause the
     Second Step Merger to be consummated. In addition, no assurance can be
     given as to whether or when the Merger Consideration will be paid to
     stockholders who do not tender their Shares in the Offer. IN NO EVENT WILL
     ANY INTEREST BE PAID ON THE MERGER CONSIDERATION. After completion or
     termination of the Offer, Parent and Purchaser also reserve the right, but
     have no current intention, to sell Shares in open market or negotiated
     transactions.
 
                               THE AMENDED OFFER
 
AMENDED TERMS OF THE OFFER
 
     The terms of the Offer set forth under the section entitled "THE TENDER
OFFER -- Terms of the Offer" of the November 2 Offer to Purchase are hereby
amended and supplemented as follows:
 
          The price to be paid for Shares purchased pursuant to the Offer has
     been increased from $37.00 to $39.125 per Share, net to the seller in cash,
     without interest thereon. Upon the terms and subject to the conditions of
     the Offer (including, if the Offer is extended or amended, the terms and
     conditions of any such extension or amendment), after the Expiration Date,
     Purchaser will promptly accept for payment and will pay for all Shares
     validly tendered prior to the Expiration Date and not properly withdrawn in
     accordance with the section entitled "THE TENDER OFFER -- Withdrawal
     Rights" of the Offer to Purchase. All stockholders whose Shares are
     tendered and purchased pursuant to the Offer (including those Shares
     tendered prior to the date hereof) will receive the increased price.
 
          THE EXPIRATION DATE OF THE OFFER HAS BEEN EXTENDED AND THE OFFER WILL
     NOW EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY TIME, ON TUESDAY, DECEMBER 22,
     1998, unless and until Purchaser extends the period of time during which
     the Offer is open, in which event the term "Expiration Date" shall refer to
     the latest time and date at which the Offer, as so extended by Purchaser,
     shall expire. Shares tendered pursuant to the Offer may be withdrawn in the
     manner set forth in the section entitled "THE TENDER OFFER -- Withdrawal
     Rights" of the Offer to Purchase at any time unless theretofore accepted
     for payment as provided in the Offer.
 
          Certain conditions of the Offer as set forth in the section entitled
     "THE TENDER OFFER -- Certain Conditions of the Offer" of the Offer to
     Purchase have been amended, as set forth in Amendment No. 3 to the Schedule
     14D-1 filed with the Commission on November 23, 1998. See "THE AMENDED
     OFFER -- Amended Conditions of the Offer". The minimum share condition to
     the Offer set forth in the November 2 Offer to Purchase has been eliminated
     and the Offer is no longer conditioned upon any minimum number of Shares
     being validly tendered and not withdrawn prior to the Expiration Date.
 
PROCEDURE FOR TENDERING SHARES
 
     The procedures for tendering Shares set forth in the section entitled "THE
TENDER OFFER -- Procedure for Tendering Shares" of the Offer to Purchase are
amended and supplemented as follows:
 
          Tendering stockholders may continue to use the original BLUE Letter of
     Transmittal and the original PINK Notice of Guaranteed Delivery previously
     circulated with the Offer to Purchase or may use the revised GRAY Letter of
     Transmittal and the revised SALMON Notice of Guaranteed Delivery circulated
     with this Supplement. Although the original BLUE Letter of Transmittal
     previously circulated
 
                                        6
<PAGE>   10
 
     with the Offer to Purchase refers only to the November 2 Offer to Purchase,
     stockholders using such document to tender their Shares will nevertheless
     receive the Revised Offer Price of $39.125 per Share for each Share validly
     tendered (and not properly withdrawn) and accepted for payment pursuant to
     the Offer, subject to the conditions of the Offer.
 
          STOCKHOLDERS WHO PREVIOUSLY TENDERED THEIR SHARES PURSUANT TO THE
     OFFER ARE NOT REQUIRED TO TAKE ANY FURTHER ACTION IN ORDER TO RECEIVE THE
     REVISED OFFER PRICE OF $39.125 PER SHARE, EXCEPT AS MAY BE REQUIRED BY THE
     PROCEDURE FOR GUARANTEED DELIVERY IF SUCH PROCEDURE WAS UTILIZED.
 
          See the section entitled "THE TENDER OFFER -- Withdrawal Rights" of
     the Offer to Purchase for the procedures for withdrawing Shares tendered
     pursuant to the Offer.
 
CERTAIN INFORMATION CONCERNING THE COMPANY
 
     Purchaser previously amended and restated in its entirety the third and
fourth full paragraphs set forth under the section entitled "THE TENDER
OFFER -- Certain Information Concerning the Company -- Projections" of the
November 2 Offer to Purchase in Amendment No. 3 to the Schedule 14D-1 filed with
the Commission on November 23, 1998, as follows:
 
          THE PROJECTIONS SET FORTH ABOVE WERE NOT PREPARED BY PARENT OR
     PURCHASER. THE PROJECTIONS ARE INCLUDED HEREIN SOLELY BECAUSE SUCH
     INFORMATION WAS FURNISHED TO PARENT ON BEHALF OF THE SPECIAL COMMITTEE. FOR
     THE REASONS SET FORTH AND REFERRED TO UNDER THE HEADINGS, "SPECIAL
     FACTORS -- BACKGROUND OF THE OFFER", " -- FAIRNESS OF THE OFFER" AND
     " -- ANALYSIS OF FINANCIAL ADVISOR TO PARENT", PARENT DISAGREES WITH
     CERTAIN IMPORTANT ASPECTS OF THE PROJECTIONS AND THE INCLUSION OF THE
     PROJECTIONS IN THIS OFFER TO PURCHASE SHOULD NOT BE REGARDED AS AN
     INDICATION THAT PARENT, PURCHASER OR PARENT'S FINANCIAL ADVISOR, OR
     PARENT'S OR PURCHASER'S OFFICERS AND DIRECTORS, CONSIDER SUCH INFORMATION
     TO BE ACCURATE OR RELIABLE. NONE OF SUCH PERSONS OR ENTITIES ASSUMES ANY
     RESPONSIBILITY FOR THE ACCURACY THEREOF.
 
          IN ADDITION, THE MATTERS DISCUSSED ABOVE UNDER THIS HEADING, "THE
     TENDER OFFER -- CERTAIN INFORMATION CONCERNING THE COMPANY -- PROJECTIONS"
     TOGETHER WITH OTHER MATTERS SET FORTH UNDER THE HEADING, "SPECIAL
     FACTORS -- BACKGROUND OF THE OFFER", "-- FAIRNESS OF THE OFFER" AND
     "-- ANALYSIS OF FINANCIAL ADVISOR TO PARENT" ARE FORWARD-LOOKING STATEMENTS
     THAT INVOLVE RISKS AND UNCERTAINTIES. STOCKHOLDERS ARE CAUTIONED THAT, IN
     ADDITION TO OTHER FACTORS SET FORTH UNDER "SPECIAL FACTORS -- BACKGROUND OF
     THE OFFER", "-- FAIRNESS OF THE OFFER" AND "--ANALYSIS OF FINANCIAL ADVISOR
     TO PARENT", THE FOLLOWING FACTORS MAY CAUSE THE COMPANY'S ACTUAL FINANCIAL
     PERFORMANCE TO DIFFER MATERIALLY FROM THOSE EXPRESSED IN SUCH
     FORWARD-LOOKING STATEMENTS; PRESSURE ON GROWTH RATES FROM COMPETITION AND
     REDIRECTED FOCUS FROM CORE BUSINESS; CURRENT ECONOMIC CONDITIONS;
     HISTORICALLY LOWER R&D PRODUCTIVITY THAN THAT PROJECTED IN THE R&D
     PROJECTIONS UTILIZED BY GOLDMAN SACHS; ABSENCE OF HISTORY OF COMPANY'S
     SUCCESSFUL COMMERCIALIZATION OF THE SIGNIFICANT NUMBER OF MAJOR NEW
     PRODUCTS REFLECTED IN SUCH R&D PROJECTIONS; TECHNOLOGICAL RISKS INHERENT IN
     R&D PIPELINE; AND ABSENCE OF HISTORY OF REVENUE AND PROFIT CONTRIBUTION
     FROM NEW PROJECTS COMPARABLE TO THAT PROJECTED IN THE R&D PROJECTIONS.
 
          THE PROTECTION OF THE DISCLOSURE LIABILITY SAFE HARBOR FOR
     FORWARD-LOOKING STATEMENTS CONTAINED IN THE PRIVATE SECURITIES LITIGA-
                                        7
<PAGE>   11
 
     TION REFORM ACT OF 1995 IS NOT APPLICABLE TO PROJECTIONS OR OTHER
     FORWARD-LOOKING INFORMATION CONTAINED IN THIS OFFER TO PURCHASE.
 
PRICE RANGE OF SHARES; DIVIDENDS
 
     The discussion set forth in the section entitled "THE TENDER OFFER -- Price
Range of Shares; Dividends" of the November 2 Offer to Purchase is hereby
amended and supplemented as follows:
 
          Tendering stockholders otherwise entitled thereto will receive the
     Company's dividend of $.05 per Share payable on January 15, 1999 to all
     stockholders of record on December 18, 1998 which was declared on November
     10, 1998.
 
          According to published sources, on December 4, 1998, the last full
     trading day prior to Parent's public announcement of the Revised Offer
     Price, the last closing price of the Shares on the Nasdaq National Market
     System was $37.25 per Share. STOCKHOLDERS ARE URGED TO OBTAIN A CURRENT
     MARKET QUOTATION FOR THE SHARES.
 
CERTAIN EFFECTS OF THE TRANSACTION
 
     The discussion set forth in the first five paragraphs in the section
entitled "THE TENDER OFFER -- Certain Effects of the Transaction" of the
November 2 Offer to Purchase is hereby restated in its entirety as follows.
 
          Effect upon the Shares.  The purchase of Publicly-held Shares by
     Purchaser pursuant to the Offer will reduce the number of Shares that might
     otherwise trade publicly and will reduce the number of holders of Shares,
     which could adversely affect the liquidity and market value of the
     remaining Publicly-held Shares. According to the Company's 10-K, as of
     February 20, 1998 there were approximately 553 holders of record of the
     Shares.
 
          Depending upon the number of Shares purchased pursuant to the Offer
     and the aggregate market value of any Shares not purchased pursuant to the
     Offer, the Shares may no longer meet the standards for continued listing
     for quotation on the Nasdaq National Market System and may, upon the
     initiative of the NASD, be delisted therefrom. The Nasdaq National Market
     System published guidelines indicate that the NASD would consider delisting
     the Shares if, among other things, the number of holders of Shares should
     fall below 400 or if the number of publicly held Shares should fall below
     750,000 or if the aggregate market value of the Publicly-held Shares should
     fall below $5,000,000.
 
          In the event that the Shares are no longer included in the Nasdaq
     National Market System, it is possible that the Shares would continue to
     trade in the over-the-counter market and that price quotations would be
     reported by other sources. The extent of the public market for the Shares
     and the availability of such quotations would, however, depend on the
     number of holders of Shares remaining at such time, the interest in
     maintaining a market in the Shares on the part of securities firms, the
     possible termination of registration of the Shares under the Exchange Act,
     as described below, and other factors. To the extent the Shares are
     delisted from quotation on the Nasdaq National Market System, the market
     for the Shares could be adversely affected. Further, Purchaser cannot
     predict whether the reduction in the number of Shares that might otherwise
     trade publicly, if any, effected by the Offer would have an adverse or
     beneficial effect on the market price for or marketability of the Shares or
     whether it would cause future market prices to be greater or less than the
     Offer Price.
 
     The Shares are currently registered under the Exchange Act. Such
     registration may be terminated upon application by the Company to the
     Commission if there are fewer than 300 holders of record of Shares. If such
     registration were terminated, the Company would no longer legally be
     required to disclose publicly in proxy materials distributed to
     stockholders the information which it now must provide under the Exchange
     Act or to make public disclosure of financial and other information in
     annual, quarterly and other reports required to be filed with the
     Commission under the Exchange Act; and the executive officers and directors
     of the Company and beneficial owners of more than 10% of the Shares would
     no longer be subject to the "short-swing" insider trading reporting and
     profit recovery provisions of the
                                        8
<PAGE>   12
 
     Exchange Act. Furthermore, if such registration were terminated, persons
     holding "restricted securities" of the Company may be deprived of their
     ability to dispose of such securities under Rule 144 or 144A promulgated
     under the Securities Act of 1933, as amended.
 
     If the registration of the Shares is not terminated and the Shares are not
     delisted after consummation of the Offer and prior to the Second Step
     Merger, then the Shares will cease to be listed on the Nasdaq National
     Market System, and the registration of the Shares under the Exchange Act
     will be terminated, following the Second Step Merger.
 
SOURCE AND AMOUNT OF FUNDS
 
     The information contained in the Section entitled "THE TENDER
OFFER -- Source and Amount of Funds" of the November 2 Offer to Purchase is
hereby amended and restated in its entirety as follows:
 
          Purchaser estimates that the total amount of funds required to
     purchase the Publicly-held Shares and the Option Shares pursuant to the
     Offer and the Second Step Merger will be approximately $470 million (after
     giving effect to the payment of the exercise price on the vested and
     exercisable Options and excluding $3.8 million for payment of estimated
     costs and expenses).
 
          Parent received a financing commitment for credit facilities (the
     "Credit Facilities") of up to $600 million from The First National Bank of
     Chicago ("First Chicago" and, in its capacity as administrative agent, the
     "Administrative Agent"). First Chicago's affiliate, First Chicago Capital
     Markets, Inc., acting as arranger (the "Arranger") with respect to the
     Credit Facilities, undertook to syndicate the Credit Facilities to a group
     of financial institutions (the "Lenders"). As of the date hereof, the
     Lenders have committed to provide the entire amount of the Credit
     Facilities.
 
          The Credit Facilities will consist of an unsecured 364-Day credit
     facility of up to $300 million (the "364-Day Facility") and an unsecured
     five-year revolving credit facility of up to $300 million (the "Revolving
     Credit Facility") that will be made available to Parent. A portion of the
     proceeds of both the 364-Day Facility and the Revolving Credit Facility
     will be used to finance the Offer. Parent will contribute approximately
     $170 million of proceeds from the 364-Day Facility and approximately $300
     million of proceeds of the Revolving Credit Facility to Purchaser (assuming
     all Publicly-held Shares and the Option Shares are purchased, after giving
     effect to the payment of the exercise price on the vested and exercisable
     Options), which funds will be used by Purchaser to pay for Shares accepted
     for payment in the Offer. Existing cash and the balance of the proceeds of
     the 364-Day Facility will be used by Parent to pay certain expenses and
     costs related to the Offer and to provide financing for the general
     corporate purposes of Parent and its subsidiaries after consummation of the
     Offer.
 
          The availability of the Credit Facilities is subject to the following
     conditions: (i) no amendment, waiver or modification of the terms of the
     Offer which is not reasonably acceptable to the Administrative Agent; (ii)
     the absence of any injunction or restraining order which, in the reasonable
     judgment of the Administrative Agent, would prohibit the funding of the
     Credit Facilities or the successful consummation of the Offer or the
     Scheduled Asset Sale (hereinafter defined); (iii) the absence of material
     litigation; (iv) the absence of any material adverse change with respect to
     Parent or Parent's principal operating subsidiaries and (v) certain other
     conditions customary for credit facilities of this type.
 
          Parent expects that the Credit Facilities will provide sufficient
     availability to finance the Offer and related costs and expenses and,
     together with other financing sources available to Parent, to provide for
     Parent's and its subsidiaries' (including, after the Second Step Merger,
     the Company's) ongoing working capital and general corporate needs.
 
          The interest rates on the Credit Facilities will be, at Parent's
     election, either the Alternate Base Rate (defined as the higher of First
     Chicago's base rate and the Federal Funds rate plus  1/2% per annum) or the
     Eurodollar Rate (defined as the sum of (i) the quotient of First Chicago's
     London interbank offering rate divided by one minus the maximum aggregate
     reserve requirement imposed under Regulation D on Eurocurrency liabilities,
     plus (ii) the applicable percentage rate per annum as set forth in the
     pricing schedule attached to the credit agreement (the "Pricing
     Schedule")). During the continuance of a
                                        9
<PAGE>   13
 
     default, the interest rate on any loan under the Credit Facilities will be
     the otherwise applicable interest rate plus 2% per annum. A facility fee
     will accrue at a per annum rate as set forth in the Pricing Schedule on the
     daily average commitment of such lender until and including the termination
     date of the Credit Facilities. A utilization fee will accrue for each day
     until and including the later of the termination date of the Credit
     Facilities and date all loans are paid in full, such utilization fee to be
     equal to the applicable utilization fee rate as set forth in the Pricing
     Schedule for such date multiplied by the aggregate principal amount of the
     loans and aggregate letter of credit obligations outstanding on such date,
     payable on each payment date and the termination date of the Credit
     Facilities.
 
          The Lenders' aggregate commitments under the 364-Day Facility will be
     reduced by (i) 100% of the net proceeds realized upon closing of the
     Scheduled Asset Sale (defined below) and (ii) 100% of the net proceeds
     realized upon the issuance or incurrence of indebtedness for borrowed money
     (exclusive of loans under the Credit Facilities), but only to the extent
     that such application of the proceeds described in the foregoing clauses
     (i) and (ii) is necessary to reduce the aggregate commitments of the
     Lenders under the 364-Day Facility to $100,000,000.
 
          The Credit Facilities will include certain representations and
     warranties and covenants customary for facilities of this type, including:
     (i) financial covenants consisting of a minimum net worth requirement and a
     maximum leverage ratio; (ii) preservation of corporate existence,
     compliance with laws, payment of taxes, maintenance of properties and
     insurance and financial and other reporting requirements; and (iii)
     limitations (subject to certain exceptions) on indebtedness, contingent
     obligations (including guarantees), liens, mergers and acquisitions, sales
     of assets, joint ventures and other investments, and transactions with
     affiliates. The Credit Facilities will also include customary events of
     default, including payment defaults, breaches of representations and
     warranties, covenant defaults, cross defaults to other indebtedness,
     bankruptcy events, defaults in satisfaction of money judgments, material
     adverse change, certain events under the Employee Retirement Income
     Security Act of 1974, as amended, and a change of control of Parent.
 
          On August 25, 1998, Parent announced that it had entered into a
     definitive agreement to sell its packaging coatings business to The Valspar
     Corporation (the "Scheduled Asset Sale"). The transaction is presently
     expected to close prior to December 31, 1998. Under the terms of the
     364-Day Facility, the net proceeds to Parent from such sale must be used to
     reduce the 364-Day Facility to a maximum of $100,000,000. Parent has made
     no additional plans or arrangements to finance or repay the Credit
     Facilities other than in accordance with the terms of the Credit Facilities
     as described herein.
 
     Purchaser's obligation to purchase Shares tendered pursuant to the Offer is
not subject to financing.
 
AMENDED CONDITIONS OF THE OFFER
 
     The Purchaser hereby amends and restates in its entirety the discussion set
forth in the section entitled "THE TENDER OFFER -- Certain Conditions of the
Offer" of the November 2 Offer to Purchase which had been previously amended, in
part, in Amendment No. 3 to the Schedule 14D-1 filed with the Commission on
November 23, 1998, as follows:
 
     CERTAIN CONDITIONS OF THE OFFER
 
          Notwithstanding any other term or provision of the Offer, Purchaser
     shall not be required to accept for payment, or, subject to any applicable
     rules and regulations of the Commission, including Rule 14e-1(c) under the
     Exchange Act (relating to Purchaser's obligation to pay for or return
     tendered Shares promptly after termination or withdrawal of the Offer),
     accept for payment, purchase or pay for any Shares of the Company tendered,
     and may terminate or amend the Offer and may postpone the acceptance for
     payment of and payment for any Shares, if at any time prior to the
     Expiration Date, any of the following shall occur or exist:
 
             (a) there shall have been threatened, instituted or be pending any
        action, proceeding, application, claim or counterclaim by any government
        or governmental authority or agency,
 
                                       10
<PAGE>   14
 
        domestic or foreign, or by any other person, domestic or foreign, before
        any court or governmental regulatory or administrative agency, authority
        or tribunal, domestic or foreign, (i) challenging the acquisition by
        Parent or Purchaser of the Shares or seeking to restrain or prohibit the
        making or consummation of the Offer or the Second Step Merger; (ii)
        seeking to obtain from Parent or Purchaser any damages, fines or legal
        sanctions relating to the Offer or the Second Step Merger; (iii) seeking
        to prohibit or limit the ownership or operation by Parent or Purchaser
        or any of their affiliates of any portion of the business or assets of
        the Company or to compel Parent or Purchaser or any of their affiliates
        to dispose of or hold separate all or any portion of the business or
        assets of the Company or seeking to impose any limitation on the ability
        of Parent or Purchaser or any of their affiliates to conduct such
        business or own such assets; (iv) seeking to impose or confirm
        limitations on the ability of Parent or Purchaser or any of their
        affiliates effectively to exercise full rights of ownership of the
        Shares, including, without limitation, the right to vote any Shares
        acquired or owned by Parent or Purchaser or any of their affiliates on
        all matters properly presented to the Company's stockholders; (v)
        seeking to require divestiture by Parent or Purchaser or any of their
        affiliates of any Shares; or (vi) which would otherwise in the judgment
        of Purchaser or Parent (which shall be reasonably exercised), materially
        adversely affect the Company or adversely affect the benefits which
        Purchaser or Parent expects to derive from the successful completion of
        the Offer and/or the Second Step Merger; or
 
             (b) there shall be any statute, rule, regulation, legislation,
        interpretation, judgment, order or injunction proposed, enacted,
        promulgated, entered, enforced, issued or deemed applicable to the
        Offer, the Second Step Merger, or other similar business combination by
        Purchaser or any affiliate of Parent with the Company, or any other
        action shall have been taken by any government, governmental authority
        or agency or court with respect to a proceeding described in paragraph
        (a) above, domestic or foreign, that has, or, in Parent's discretion
        (which shall be reasonably exercised), could be expected to result in,
        any of the consequences referred to in paragraph (a) above; or
 
             (c) any approval, permit, authorization, favorable review or
        consent of any court or governmental entity shall not have been obtained
        on terms satisfactory to Parent or Purchaser in their discretion (which
        shall be reasonably exercised) or Parent or Purchaser is advised, or
        otherwise has reason to believe, that any such approval, permit,
        authorization, review or consent will be denied or substantially
        delayed, or will not be given other than upon terms or conditions that
        would, in Parent's or Purchaser's judgment (which shall be reasonably
        exercised), make it impracticable to proceed with the Offer; or
 
             (d) any change shall have occurred or been threatened (or any
        condition, event or development shall have occurred or been threatened
        involving a prospective change) in the business, properties, assets,
        liabilities, capitalization, stockholder's equity, condition (financial
        or otherwise), operations, licenses or franchises, results of operations
        or prospects of the Company that, in the judgment of Parent(which shall
        be reasonably exercised), is or may be materially adverse to the Company
        or to the value of the Shares to Purchaser, Parent or any other
        affiliate of Parent or Purchaser, or Parent or Purchaser shall have
        become aware of any facts that, in the judgment of Parent or Purchaser
        (which shall be reasonably exercised), have or may have material adverse
        significance with respect to either the value of the Company or the
        value of the Shares to Purchaser, Parent or any other affiliate of
        Parent; or
 
             (e) there shall have occurred or been threatened (i) any general
        suspension of trading in, or limitation on prices for, securities on the
        New York Stock Exchange, Inc., any other national securities exchange or
        in the over-the-counter market in the United States; (ii) the
        declaration of a banking moratorium or any suspension of payments in
        respect of banks in the United States (whether or not mandatory); (iii)
        any extraordinary or material adverse change in the financial markets or
        major stock exchange indices in the United States or abroad or in the
        market price of Shares; (iv) any material change in United States
        currency exchange rates or any other currency exchange rates or a
        suspension of, or limitation on, the markets therefor; (v) the
        commencement of a war or armed hostilities or other international
        calamity directly or indirectly involving the United
                                       11
<PAGE>   15
 
        States; or (vi) in the case of any of the foregoing existing at the time
        of the commencement of the Offer, a material acceleration or worsening
        thereof; or
 
             (f) unless Parent shall have consented in writing, the Company
        shall have (i) split, combined or otherwise changed, or authorized or
        proposed a split, combination or other change of, the Shares or its
        capitalization; (ii) issued, distributed, pledged or sold, or
        authorized, proposed or announced the issuance, distribution, pledge or
        sale of (A) any shares of capital stock (including, without limitation,
        the Shares), or securities convertible into any such shares, or any
        rights, warrants or options to acquire any such shares or convertible
        securities, or (B) any other securities in respect of, in lieu of, or in
        substitution for Shares; (iii) purchased or otherwise acquired or caused
        a reduction in the number of, or proposed or offered to purchase or
        otherwise acquire or cause a reduction in the number of, any outstanding
        Shares or other securities of the Company; (iv) declared or paid any
        dividend or distribution on any shares of capital stock or issued, or
        authorized, recommended or proposed the issuance of, any other
        distribution in respect of the Shares, whether payable in cash,
        securities or other property, or altered or proposed to alter any
        material term of any outstanding security; (v) issued, or announced its
        intention to issue, any debt securities or any rights, warrants or
        options entitling the holder thereof to purchase or otherwise acquire
        any debt securities, or incurred, or announced its intention to incur,
        any debt other than in the ordinary course of business and consistent
        with its past practice; (vi) authorized, recommended, proposed or
        publicly announced its intention to enter into (A) any merger,
        consolidation, liquidation, dissolution, business combination,
        acquisition of assets or securities or disposition of assets or
        securities other than in the ordinary course of business, (B) any
        material change in its capitalization, (C) any release or relinquishment
        of any material contract rights, or (D) any comparable event not in the
        ordinary course of business; (vii) authorized, recommended or proposed
        or announced its intention to authorize, recommend or propose any
        transaction which could adversely affect the value of the Shares; (viii)
        proposed, adopted or authorized any amendment to its Certificate of
        Incorporation or Bylaws or similar organizational documents or Purchaser
        or Parent shall have learned about any such proposal or amendment which
        shall not have been previously disclosed; (ix) entered into any new
        material contracts or canceled or substantially changed the terms of any
        existing material contracts; or (x) agreed in writing or otherwise to
        take any of the foregoing actions; or
 
             (g) the Company shall have (i) entered into any employment,
        severance or similar agreement, arrangement or plan with any of its
        employees other than in the ordinary course of business; (ii) entered
        into or amended any agreements, arrangements or plans so as to provide
        for increased or accelerated benefits to any employee as a result of or
        in connection with the transactions contemplated by the Offer, the
        Second Step Merger or other business combination; or (iii) except as may
        be required by law, taken any action to terminate or amend any employee
        benefit plan (as defined in Section 3(2) of the Employee Retirement and
        Income Security Act of 1974, as amended) of the Company, or Purchaser
        shall have become aware of any such action that was not disclosed in
        publicly available filings prior to the date of this Offer to Purchase;
        or
 
             (h) Purchaser, Parent or another affiliate of Parent and the
        Company shall have entered into an agreement that the Offer be
        terminated or amended or Purchaser, Parent or another affiliate of
        Parent shall have entered into an agreement with the Company providing
        for a merger or other business combination with the Company,
 
     which, in the judgment of Parent or Purchaser (which shall be reasonably
     exercised) in any such case, and regardless of the circumstances (including
     any action or inaction by Purchaser, Parent or any affiliate of Parent)
     giving rise to any such condition, makes it inadvisable to proceed with the
     Offer and/or with such acceptance for payment or payment.
 
          The foregoing conditions are for the sole benefit of Parent and
     Purchaser and may be asserted by Parent or Purchaser regardless of the
     circumstances giving rise to any such condition and may be waived by Parent
     or Purchaser, in whole or in part, at any time and from time to time, in
     its discretion. The failure by Parent or Purchaser at any time to exercise
     any of the foregoing rights will not be deemed a waiver of any such right,
     and the waiver of such right with respect to any particular facts or
     circumstances
                                       12
<PAGE>   16
 
     shall not be deemed a waiver with respect to any other facts or
     circumstances, and each such right will be deemed an ongoing right which
     may be asserted at any time and from time to time. Any determination by
     Parent or Purchaser concerning the events described above will be final and
     binding upon all parties.
 
          Should the Offer be terminated pursuant to the foregoing provisions,
     all tendered Shares not theretofore accepted for payment shall forthwith be
     returned by the Depositary to the tendering stockholders.
 
MISCELLANEOUS
 
     The information set forth in the section entitled "THE TENDER
OFFER -- Miscellaneous" of the November 2 Offer to Purchase is hereby amended
and restated in its entirety as follows:
 
          Neither Parent nor Purchaser is aware of any state where the making of
     the Offer is prohibited by administrative or judicial action pursuant to
     any valid state statute. If Parent or Purchaser becomes aware of any valid
     state statute prohibiting the making of the Offer or the acceptance of
     Shares pursuant thereto, Parent and Purchaser will make a good faith effort
     to comply with such state statute. If, after such good faith effort, the
     Offer cannot comply with such state statute, the Offer will not be made to
     (nor will tenders be accepted from or on behalf of) the holders of Shares
     in such state. Each of Parent or Purchaser may, in its discretion, however,
     take such action as it may deem necessary to make the Offer in any
     jurisdiction and extend the Offer to holders of Shares in any such
     jurisdiction. In any jurisdiction where the securities, blue sky or other
     laws require the offer to be made by a licensed broker or dealer, the Offer
     shall be deemed to be made on behalf of Purchaser by the Dealer Manager or
     one or more registered brokers or dealers licensed under the laws of such
     jurisdiction.
 
          NO PERSON HAS BEEN AUTHORIZED TO GIVE ANY INFORMATION OR TO MAKE ANY
     REPRESENTATION ON BEHALF OF PURCHASER OR PARENT NOT CONTAINED HEREIN, IN
     THE OFFER TO PURCHASE OR IN THE LETTER OF TRANSMITTAL AND, IF GIVEN OR
     MADE, SUCH INFORMATION OR REPRESENTATION MUST NOT BE RELIED UPON AS HAVING
     BEEN AUTHORIZED. NEITHER THE DELIVERY OF THIS SUPPLEMENT TO THE OFFER TO
     PURCHASE NOR ANY PURCHASE PURSUANT TO THE OFFER SHALL, UNDER ANY
     CIRCUMSTANCES, CREATE ANY IMPLICATION THAT THERE HAS BEEN NO CHANGE IN THE
     AFFAIRS OF PURCHASER, PARENT OR THE COMPANY SINCE THE DATE AS OF WHICH
     INFORMATION IS FURNISHED OR THE DATE OF THIS SUPPLEMENT.
 
          Purchaser and Parent have filed with the Commission a Tender Offer
     Statement on Schedule 14D-1, together with exhibits, pursuant to Rule 14d-3
     under the Exchange Act, furnishing certain additional information with
     respect to the Offer. In addition, Parent and Purchaser have filed with the
     Commission the Schedule 13E-3, together with exhibits, pursuant to Rule
     13e-3 under the Exchange Act. Such Schedules and any amendments thereto,
     including exhibits, may be inspected and copies may be obtained from the
     Commission in the manner set forth herein (except that they will not be
     available at the regional offices of the Commission).
                                          DEXTER ACQUISITION DELAWARE, INC.
December 7, 1998
 
                                       13
<PAGE>   17
 
     Manually signed facsimile copies of the Letter of Transmittal will be
accepted. Revised Letters of Transmittal and certificates for Shares should be
sent or delivered by each stockholder of the Company or his broker, dealer,
commercial bank or trust company to the Depositary at one of its addresses set
forth below:
                        The Depositary for the Offer is:
                                BANKBOSTON, N.A.
 
<TABLE>
<S>                                <C>                                <C>
             By Mail:                           By Hand:                    By Overnight Delivery:
         BankBoston, N.A.           Securities Transfer & Reporting            BankBoston, N.A.
          P. O. Box 9573                     Services, Inc.                  40 Campanelli Drive
 Boston, Massachusetts 02205-9573      c/o Boston EquiServe L.P.        Braintree, Massachusetts 02184
       Attention: Corporate               100 Williams Street                Attention: Corporate
          Reorganization                        Galleria                        Reorganization
                                        New York, New York 10038
                                          Attention: Corporate
                                             Reorganization
 
                                       By Facsimile Transmission:
                                      (Eligible Institutions Only)
                                             (781) 794-6333
                                       Confirm Fax by Telephone:
                                             (781) 794-6388
</TABLE>
 
     Questions and requests for assistance should be directed to the Information
Agent at its address or telephone numbers set forth below. Additional copies of
the Offer to Purchase, this Supplement, the Letter of Transmittal and all other
tender offer materials may be obtained from the Information Agent as set forth
below, and will be furnished promptly at the Purchaser's expense. You may also
contact your broker, dealer, commercial bank, trust company or other nominee for
assistance concerning the Offer.
 
                    The Information Agent for the Offer is:
 
                                [MACKENZIE LOGO]
                                156 Fifth Avenue
                            New York, New York 10010
                         (212) 929-5500 (Call Collect)
                                       or
                         CALL TOLL-FREE (800) 322-2885
                      The Dealer Manager for the Offer is:
                              MERRILL LYNCH & CO.
                             World Financial Center
                                  North Tower
                         New York, New York 10281-1314
                         (212) 449-8971 (Call Collect)

<PAGE>   1
 
                             LETTER OF TRANSMITTAL
 
                        TO TENDER SHARES OF COMMON STOCK
 
                                       OF
 
                            LIFE TECHNOLOGIES, INC.
            PURSUANT TO THE OFFER TO PURCHASE DATED NOVEMBER 2, 1998
                                    AND THE
                       SUPPLEMENT DATED DECEMBER 7, 1998
 
                                       BY
 
                       DEXTER ACQUISITION DELAWARE, INC.
                          A WHOLLY-OWNED SUBSIDIARY OF
 
                               DEXTER CORPORATION
 
         THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT,
NEW YORK CITY TIME, ON TUESDAY, DECEMBER 22, 1998, UNLESS THE OFFER IS EXTENDED.
 
                        The Depositary for the Offer is:
 
                                BANKBOSTON, N.A.
 
<TABLE>
<S>                                <C>                                <C>
             By Mail:                           By Hand:                    By Overnight Delivery:
         BankBoston, N.A.           Securities Transfer & Reporting            BankBoston, N.A.
          P.O. Box 9573                      Services, Inc.                  40 Campanelli Drive
 Boston, Massachusetts 02205-9573      c/o Boston EquiServe L.P.        Braintree, Massachusetts 02184
       Attention: Corporate               100 Williams Street                Attention: Corporate
          Reorganization                        Galleria                        Reorganization
                                        New York, New York 10038
                                          Attention: Corporate
                                             Reorganization
</TABLE>
 
                           By Facsimile Transmission:
                          (Eligible Institutions Only)
                                 (781) 794-6333
 
                           Confirm Fax by Telephone:
                                 (781) 794-6388
                            -----------------------
 
     DELIVERY OF THIS LETTER OF TRANSMITTAL TO AN ADDRESS, OR TRANSMISSION OF
INSTRUCTIONS VIA FACSIMILE, OTHER THAN AS SET FORTH ABOVE WILL NOT CONSTITUTE A
VALID DELIVERY TO THE DEPOSITARY. YOU MUST SIGN THIS LETTER OF TRANSMITTAL WHERE
INDICATED BELOW AND COMPLETE THE SUBSTITUTE FORM W-9 PROVIDED BELOW.
 
     THE INSTRUCTIONS ACCOMPANYING THIS LETTER OF TRANSMITTAL SHOULD BE READ
CAREFULLY BEFORE THIS LETTER OF TRANSMITTAL IS COMPLETED.
 
     Either this gray Letter of Transmittal or the blue Letter of Transmittal
delivered with the Offer to Purchase must be completed by stockholders of Life
Technologies, Inc. (the "Company") if certificates representing Shares (as
defined below) ("Share Certificates") are to be forwarded with a Letter of
Transmittal or, unless an Agent's Message (as defined in the Supplement (as
defined below)) is utilized, if delivery of Shares is to be made by book-entry
transfer to the Depositary's account at The Depository Trust Company ("DTC")
(the "Book-Entry Transfer Facility") pursuant to the procedures set forth in the
sections entitled "THE TENDER OFFER -- Procedure for Tendering Shares" of the
Offer to Purchase.
 
     Stockholders whose Share Certificates are not immediately available or who
cannot deliver their Share Certificates and all other documents required hereby
to the Depositary prior to the Expiration Date (as defined in the Supplement (as
defined below)) or who cannot comply with the book-entry transfer procedures on
a timely basis, may nevertheless tender their Shares pursuant to the guaranteed
delivery procedures set forth in the sections entitled "THE TENDER OFFER --
Procedure for Tendering Shares" of the Offer to Purchase and "THE AMENDED
OFFER -- Procedure for Tendering Shares" of the Supplement. See Instruction 2.
DELIVERY OF DOCUMENTS TO THE BOOK-ENTRY TRANSFER FACILITY DOES NOT CONSTITUTE
DELIVERY TO THE DEPOSITARY.
<PAGE>   2
 
<TABLE>
<CAPTION>
 
- -----------------------------------------------------------------------------------------------------------------
                                 NAME(S) AND ADDRESS(ES) OF REGISTERED OWNER(S)
                   (PLEASE FILL IN, IF BLANK, EXACTLY AS NAME(S) APPEAR(S) ON CERTIFICATE(S))
<S>                                                      <C>
- -----------------------------------------------------------------------------------------------------------------
 
- -----------------------------------------------------------------------------------------------------------------
                                   (TAX IDENTIFICATION OR SOCIAL SECURITY NO.)
- -----------------------------------------------------------------------------------------------------------------
</TABLE>
 
<TABLE>
<CAPTION>
 
- -----------------------------------------------------------------------------------------------------------------
                                         DESCRIPTION OF SHARES ENCLOSED
- -----------------------------------------------------------------------------------------------------------------
                                             CERTIFICATE(S) ENCLOSED
                                      (ATTACH ADDITIONAL LIST IF NECESSARY)
<S>                                                      <C>
- -----------------------------------------------------------------------------------------------------------------
                                                                          TOTAL NUMBER OF SHARES
  CERTIFICATE NUMBER(S)                                               REPRESENTED BY CERTIFICATE(S)
- -----------------------------------------------------------------------------------------------------------------
 
- -----------------------------------------------------------------------------------------------------------------
 
- -----------------------------------------------------------------------------------------------------------------
 
- -----------------------------------------------------------------------------------------------------------------
 
- -----------------------------------------------------------------------------------------------------------------
 
  TOTAL SHARES TENDERED*
- -----------------------------------------------------------------------------------------------------------------
 
  TOTAL SHARES
- -----------------------------------------------------------------------------------------------------------------
 
- -----------------------------------------------------------------------------------------------------------------
 
  * UNLESS OTHERWISE INDICATED, IT WILL BE ASSUMED THAT ALL SHARES REPRESENTED BY ANY CERTIFICATES DELIVERED TO
    THE DEPOSITARY ARE BEING TENDERED. SEE INSTRUCTION 4.
- -----------------------------------------------------------------------------------------------------------------
</TABLE>
 
[ ] CHECK HERE IF SHARES ARE BEING DELIVERED BY BOOK-ENTRY TRANSFER TO THE
    DEPOSITARY'S ACCOUNT AT THE BOOK-ENTRY TRANSFER FACILITY AND COMPLETE THE
    FOLLOWING:
 
   Name of Tendering Institution:
   -----------------------------------------------------------------------------
 
   Account Number at DTC:
   -----------------------------------------------------------------------------
 
   Transaction Code Number:
   -----------------------------------------------------------------------------
 
[ ] CHECK HERE IF SHARES ARE BEING DELIVERED PURSUANT TO A NOTICE OF GUARANTEED
    DELIVERY PREVIOUSLY SENT TO THE DEPOSITARY AND COMPLETE THE FOLLOWING:
 
   Name(s) of Registered Holder(s):
   -----------------------------------------------------------------------------
 
   Window Ticket No. (if any): ------------------------------------------------
 
   Date of Execution of Notice of Guaranteed Delivery: ------------------------
 
   Name of Institution which Guaranteed Delivery: -----------------------------
<PAGE>   3
 
                    NOTE: SIGNATURES MUST BE PROVIDED BELOW.
              PLEASE READ THE ACCOMPANYING INSTRUCTIONS CAREFULLY.
 
Ladies and Gentlemen:
 
     The undersigned hereby tenders to Dexter Acquisition Delaware, Inc., a
Delaware corporation ("Purchaser"), and a wholly-owned subsidiary of Dexter
Corporation, a Connecticut corporation ("Parent"), the above-described shares of
common stock, par value $0.01 per share (the "Shares"), of Life Technologies,
Inc., a Delaware corporation (the "Company"), not owned by Parent, pursuant to
Purchaser's offer to purchase all outstanding Shares at a purchase price of
$39.125 per Share (the "Offer Price"), net to the seller in cash, without
interest, upon the terms and subject to the conditions set forth in the Offer to
Purchase dated November 2, 1998 (the "Offer to Purchase"), the Supplement
thereto dated December 7, 1998 (the "Supplement"), receipt of which is hereby
acknowledged, and in this Letter of Transmittal (which, together with the Offer
to Purchase and the Supplement, constitute the "Offer").
 
     Subject to, and effective upon, acceptance for payment of the Shares
tendered herewith, the undersigned hereby sells, assigns and transfers to, or
upon the order of Purchaser, all right, title and interest in and to all the
Shares that are being tendered hereby and any and all other Shares or securities
issued or issuable in respect thereof on or after November 2, 1998 (a
"Distribution") and appoints the Depositary the true and lawful agent and
attorney-in-fact of the undersigned with respect to such Shares (and any
Distributions) with full power of substitution (such power of attorney being
deemed to be an irrevocable power coupled with an interest), to (a) deliver
Share Certificates (and any Distributions), or transfer ownership of such Shares
(and any Distributions) on the account books maintained by the Book-Entry
Transfer Facility, together in any such case with all accompanying evidences of
transfer and authenticity, to or upon the order of Purchaser, (b) present such
Shares (and any Distributions) for transfer on the books of the Company and (c)
receive all benefits and otherwise exercise all rights of beneficial ownership
of such Shares, all in accordance with the terms of and subject to the
conditions of the Offer.
 
     The undersigned hereby irrevocably appoints designees of Purchaser as the
attorneys and proxies of the undersigned, each with full power of substitution,
to exercise all voting and other rights of the undersigned in such manner as
each such attorney and proxy or his substitute shall in his sole judgment deem
proper, with respect to all of the Shares tendered hereby which have been
accepted for payment by Purchaser prior to the time of any vote or other action
(and any Distributions), at any meeting of stockholders of the Company (whether
annual or special and whether or not an adjourned meeting) or otherwise. This
power of attorney and proxy are irrevocable, are coupled with an interest in the
Shares tendered hereby and are granted in consideration of, and effective upon,
the acceptance for payment of such Shares by Purchaser in accordance with the
terms of the Offer. Such acceptance for payment shall revoke any other proxy and
written consent granted by the undersigned at any time with respect to such
Shares (and any Distributions) and no subsequent proxies will be given or
written consents executed by the undersigned (and if given or executed will be
not be deemed effective).
 
     The undersigned hereby represents and warrants that the undersigned has
full power and authority to tender, sell, assign and transfer the Shares
tendered hereby (and any Distributions) and that, when the same are accepted for
payment by Purchaser, Purchaser will acquire good and unencumbered title
thereto, free and clear of all liens, restrictions, charges and encumbrances and
not subject to any adverse claims. The undersigned will, upon request, execute
and deliver any additional documents deemed by the Depositary or Purchaser to be
necessary or desirable to complete the sale, assignment and transfer of the
Shares tendered hereby (and any Distributions). All authority herein conferred
or agreed to be conferred shall survive the death or incapacity of the
undersigned and any obligation of the undersigned hereunder shall be binding
upon the heirs, personal representatives, successors and assigns of the
undersigned. Except as stated in the Offer, this tender is irrevocable.
 
     The undersigned understands that tenders of Shares pursuant to any one of
the procedures described in the sections entitled "THE TENDER OFFER -- Procedure
for Tendering Shares" of the Offer to Purchase and "THE AMENDED
OFFER -- Procedure for Tendering Shares" of the Supplement and in the
instructions hereto will constitute an agreement between the undersigned and
Purchaser upon the terms and subject to the conditions of the Offer. The
undersigned acknowledges that no interest will be paid on the Offer Price for
tendered Shares regardless of any extension of the Offer or any delay in making
such payment.
<PAGE>   4
 
     Unless otherwise indicated herein in the box entitled "Special Payment
Instructions," please issue the check for the purchase price of any Shares
purchased, and return any Share Certificates evidencing any Shares not tendered
or not purchased, in the name(s) of the undersigned (and, in the case of Shares
tendered by book-entry transfer, by credit to the account at the Book-Entry
Transfer Facility). Similarly, unless otherwise indicated in the box entitled
"Special Delivery Instructions," please mail the check for the purchase price of
any Shares purchased and return any Share Certificates not tendered or not
purchased (and accompanying documents, as appropriate) to the undersigned at the
address shown below the undersigned's signature(s). In the event that the boxes
entitled "Special Delivery Instructions" and "Special Payment Instructions" are
both completed, please issue the check for the purchase price of any Shares
purchased and return any Share Certificates evidencing any Shares not tendered
or not purchased in the name(s) of, and mail said check and Share Certificates
to, the person(s) so indicated. The undersigned acknowledges that Purchaser has
no obligation, pursuant to the "Special Payment Instructions," to transfer any
Shares from the name of the registered holder(s) thereof if Purchaser does not
accept for payment any of the Shares so tendered.
 
     Effective upon the receipt of payment for tendered Shares by the
undersigned stockholder(s), the undersigned stockholder(s), on behalf of
themselves and on behalf of any beneficial owner of the tendered Shares, and on
behalf of all spouses, heirs, predecessors, successors, assigns,
representatives, agents, parent or subsidiary corporations of such tendering
stockholder(s) or such beneficial owner of the tendered Shares (including
without limitation any trust of which the undersigned tendering stockholder(s)
is the trustee or which is for the benefit of any undersigned tendering
stockholder(s) or member of his family), releases and discharges any and all
claims that any such person or entity has, had or may have against Parent,
Purchaser, the Company and, without limitation, the Other Related Persons (as
defined in the following sentence) arising out of, or related to, the price
offered in the Offer or the consideration received by tendering stockholder(s)
in the Offer. The term "Other Related Persons" as used in the preceding sentence
shall mean each of Purchaser's past or present directors, officers, employees,
partners, principals, agents, insurers or co-insurers, controlling stockholders,
parent or subsidiary corporations, affiliates, attorneys, advisors, legal
representatives, and assigns.
<PAGE>   5
 
          ------------------------------------------------------------
 
                          SPECIAL PAYMENT INSTRUCTIONS
                        (SEE INSTRUCTIONS 1, 5, 6 AND 7)
 
        To be completed ONLY if the check for the purchase price of Shares
   purchased or Share Certificates evidencing Shares not tendered or not
   purchased are to be issued in the name of someone other than the
   undersigned, or if Shares tendered hereby and delivered by book-entry
   transfer which are not purchased are to be returned by credit to an
   account at the Book-Entry Transfer Facility other than that designated
   above.
 
   Issue  [ ] Check  [ ] Share Certificate(s) to:
 
   Name:
   ----------------------------------------------------
                                    (PLEASE PRINT)
 
   Address:
   --------------------------------------------------
 
   ------------------------------------------------------------
 
   ------------------------------------------------------------
                               (INCLUDE ZIP CODE)
 
   ------------------------------------------------------------
                  (TAXPAYER IDENTIFICATION OR SOCIAL SECURITY
                       NUMBER) (SEE SUBSTITUTE FORM W-9)
 
          ------------------------------------------------------------
          ------------------------------------------------------------
 
                         SPECIAL DELIVERY INSTRUCTIONS
                        (SEE INSTRUCTIONS 1, 5, 6 AND 7)
 
        To be completed ONLY if the check for the purchase price of Shares
   purchased or Share Certificates evidencing Shares not tendered or not
   purchased are to be mailed to someone other than the undersigned, or to
   the undersigned at an address other than that shown under the
   undersigned's signature.
 
   Mail  [ ] Check  [ ] Share Certificate(s) to:
 
   Name:
   ----------------------------------------------------
                                    (PLEASE PRINT)
 
   Address:
   --------------------------------------------------
 
   ------------------------------------------------------------
 
   ------------------------------------------------------------
                               (INCLUDE ZIP CODE)
 
   ------------------------------------------------------------
                  (TAXPAYER IDENTIFICATION OR SOCIAL SECURITY
                       NUMBER) (SEE SUBSTITUTE FORM W-9)
 
          ------------------------------------------------------------
<PAGE>   6
 
                                   IMPORTANT
 
                            STOCKHOLDERS: SIGN HERE
                  (PLEASE COMPLETE SUBSTITUTE FORM W-9 BELOW)
 
- --------------------------------------------------------------------------------
 
- --------------------------------------------------------------------------------
                        (SIGNATURE(S) OF STOCKHOLDER(S))
 
Dated:
- ---------------------------
 
(Must be signed by registered holder(s) exactly as name(s) appear(s) on share
certificate(s) or on a security position listing or by person(s) authorized to
become registered holder(s) by certificates and documents transmitted herewith.
If signature is by a trustee, executor, administrator, guardian,
attorney-in-fact, agent, officer of a corporation or other person acting in a
fiduciary or representative capacity, please provide the following information
and see Instruction 5.)
 
Name(s) ------------------------------------------------------------------------
 
- --------------------------------------------------------------------------------
                                 (PLEASE PRINT)
 
Capacity (Full Title)
                ----------------------------------------------------------------
 
Address-------------------------------------------------------------------------
 
- --------------------------------------------------------------------------------
                               (INCLUDE ZIP CODE)
 
Area Code and Telephone Number (   )
                                ------------------------------------------------
 
Tax Identification or Social Security Number:
                                  ----------------------------------------------
                                         (SEE SUBSTITUTE FORM W-9 BELOW)
 
                           GUARANTEE OF SIGNATURE(S)
                           (SEE INSTRUCTIONS 1 AND 5)
 
Authorized Signature
                ----------------------------------------------------------------
 
Name  --------------------------------------------------------------------------
                             (PLEASE PRINT OR TYPE)
 
Title---------------------------------------------------------------------------
 
Name of Firm
           ---------------------------------------------------------------------
 
Address-------------------------------------------------------------------------
                               (INCLUDE ZIP CODE)
 
Area Code and Telephone Number (   )
                                ------------------------------------------------
 
Dated:
- ---------------------------
<PAGE>   7
 
                                  INSTRUCTIONS
 
             FORMING PART OF THE TERMS AND CONDITIONS OF THE OFFER
 
     1.  Guarantee of Signatures.  Except as otherwise provided below,
signatures on all Letters of Transmittal must be guaranteed by a firm that is a
bank, broker, dealer, credit union, savings association or other entity which is
a member in good standing of the Securities Transfer Agents Medallion Program or
by any other bank, broker, dealer, credit union, savings association or other
entity which is an "eligible guarantor institution," as such term is defined in
Rule 17Ad-15 under the Securities Exchange Act of 1934, as amended (each of the
foregoing constituting an "Eligible Institution"), unless the Shares tendered
thereby are tendered (i) by a registered holder of Shares who has not completed
either the box labeled "Special Payment Instructions" or the box labeled
"Special Delivery Instructions" on the Letter of Transmittal or (ii) for the
account of an Eligible Institution. See Instruction 5. If Share Certificates are
registered in the name of a person or persons other than the signer of this
Letter of Transmittal, or if payment is to be made or delivered to, or
certificates evidencing unpurchased Shares are to be issued or returned to, a
person other than the registered owner or owners, then the tendered Share
Certificates must be endorsed or accompanied by duly executed stock powers, in
either case signed exactly as the name or names of the registered owner or
owners appear on the Share Certificates or stock powers, with the signatures on
the Share Certificates or stock powers guaranteed by an Eligible Institution as
provided herein. See Instruction 5.
 
     2.  Delivery of Letter of Transmittal and Share Certificates.  This Letter
of Transmittal is to be used either if Share Certificates are to be forwarded
herewith or, unless an Agent's Message (as defined in the Offer to Purchase) is
utilized, if the delivery of Shares is to be made by book-entry transfer
pursuant to the procedures set forth in the section entitled "THE TENDER
OFFER -- Procedure for Tendering Shares" of the Offer to Purchase. Certificates
for all physically delivered Shares, or a confirmation of a book-entry transfer
into the Depositary's account at the Book-Entry Transfer Facility of all Shares
delivered electronically, as well as a properly completed and duly executed
Letter of Transmittal (or a manually signed facsimile thereof) and any other
documents required by this Letter of Transmittal, or an Agent's Message in the
case of a book-entry delivery, must be received by the Depositary at one of its
addresses set forth on the front page of this Letter of Transmittal by the
Expiration Date. Stockholders who cannot deliver their Share Certificates and
all other required documents to the Depositary by the Expiration Date may tender
their Shares pursuant to the guaranteed delivery procedure set forth in the
sections entitled "THE TENDER OFFER -- Procedure for Tendering Shares" of the
Offer to Purchase and "THE AMENDED OFFER -- Procedure for Tendering Shares" of
the Supplement. Pursuant to such procedure: (i) such tender must be made by or
through an Eligible Institution; (ii) a properly completed and duly executed
Notice of Guaranteed Delivery, substantially in the form provided by Purchaser,
must be received by the Depositary prior to the Expiration Date; and (iii) the
Share Certificates for all tendered Shares in proper form for tender or a
confirmation of a book-entry transfer into the Depositary's account at the
Book-Entry Transfer Facility of all Shares delivered electronically, as well as
a properly completed and duly executed Letter of Transmittal (or a manually
signed facsimile thereof), and any other documents required by this Letter of
Transmittal, must be received by the Depositary within three NASDAQ trading days
after the date of execution of such Notice of Guaranteed Delivery, all as
provided in the section entitled "THE TENDER OFFER -- Procedure for Tendering
Shares" of the Offer to Purchase. A "NASDAQ trading day" is any day on which The
Nasdaq Stock Market, Inc.'s Nasdaq National Market is open for business.
 
     THE METHOD OF DELIVERY OF THIS LETTER OF TRANSMITTAL, SHARE CERTIFICATES
AND ALL OTHER REQUIRED DOCUMENTS, INCLUDING DELIVERY THROUGH THE BOOK-ENTRY
TRANSFER FACILITY, IS AT THE OPTION AND RISK OF THE TENDERING PERSON AND THE
DELIVERY WILL BE DEEMED MADE ONLY WHEN ACTUALLY RECEIVED BY THE DEPOSITARY. IF
DELIVERY IS BY MAIL, REGISTERED MAIL WITH RETURN RECEIPT REQUESTED, PROPERLY
INSURED, IS RECOMMENDED. IN ALL CASES, SUFFICIENT TIME SHOULD BE ALLOWED TO
ENSURE TIMELY DELIVERY.
 
     No alternative, conditional or contingent tenders will be accepted. By
execution of this Letter of Transmittal (or a manually signed facsimile
thereof), all tendering stockholders waive any right to receive any notice of
the acceptance of their Shares for payment.
 
     3.  Inadequate Space.  If the space provided herein is inadequate, the
certificate numbers and/or the number of Shares should be listed on a separate
schedule attached hereto.
<PAGE>   8
 
     4.  Partial Tenders.  (Not applicable to stockholders who tender by
book-entry transfer.) If fewer than all the Shares represented by any Share
Certificate delivered to the Depositary are to be tendered, fill in the number
of Shares which are to be tendered on the line entitled "Total Shares Tendered."
In such case, a new Share Certificate(s) for the remainder of the Shares
represented by the old Share Certificate(s) will be sent to the person(s)
signing this Letter of Transmittal, unless otherwise provided in the box
entitled "Special Delivery Instructions" herein, as promptly as practicable
following the expiration or termination of the Offer. All Shares represented by
Share Certificates delivered to the Depositary will be deemed to have been
tendered unless otherwise indicated.
 
     5.  Signatures on Letter of Transmittal; Stock Powers and Endorsements.  If
this Letter of Transmittal is signed by the registered holder(s) of the Shares
tendered hereby, the signature(s) must correspond exactly with the name(s) as
written on the face of the certificates without alteration, enlargement or any
change whatsoever.
 
     If any of the Shares tendered hereby are owned of record by two or more
persons, all such persons must sign this Letter of Transmittal.
 
     If any of the Shares tendered hereby are registered in different names on
different certificates, it will be necessary to complete, sign and submit as
many separate Letters of Transmittal as there are different registrations of
certificates.
 
     If this Letter of Transmittal is signed by the registered holder(s) of the
Shares tendered hereby, no endorsements of Share Certificate(s) or separate
stock powers are required, unless payment of the purchase price is to be made or
Share Certificate(s) evidencing Shares not tendered or not purchased are to be
returned, in the name of any person other than the registered holder(s).
Signatures on any such Share Certificates or stock powers must be guaranteed by
an Eligible Institution.
 
     If this Letter of Transmittal is signed by a person other than the
registered holder(s) of the Shares tendered hereby, the Share Certificate(s)
evidencing the Shares tendered hereby must be endorsed or accompanied by,
appropriate stock powers, in either case, signed exactly as the name(s) of the
registered holder(s) appear(s) on such Share Certificate(s). Signature(s) on any
such Share Certificate(s) or stock powers must be guaranteed by an Eligible
Institution.
 
     If this Letter of Transmittal or any Share Certificate or stock power is
signed by a trustee, executor, administrator, guardian, attorney-in-fact,
officer of a corporation or other person acting in a fiduciary or representative
capacity, such person should so indicate when signing, and proper evidence
satisfactory to Purchaser of the authority of such person so to act must be
submitted.
 
     6.  Stock Transfer Taxes.  Purchaser will pay any stock transfer taxes with
respect to the transfer and sale of any Shares to it or its order pursuant to
the Offer. If, however, payment of the purchase price is to be made to, or
Shares not tendered or not purchased are to be returned in the name of, any
person other than the registered holder(s), then the amount of any stock
transfer taxes (whether imposed on the registered holder(s), such person or
otherwise) payable on account of the transfer to such person will be deducted
from the purchase price unless satisfactory evidence of the payment of such
taxes or exemption therefrom is submitted. EXCEPT AS PROVIDED IN THIS
INSTRUCTION 6, IT WILL NOT BE NECESSARY FOR TRANSFER TAX STAMPS TO BE AFFIXED TO
THE CERTIFICATE(S) LISTED IN THIS LETTER OF TRANSMITTAL.
 
     7.  Special Payment and Delivery Instructions.  If the check for the
purchase price is to be issued, or any Shares not tendered or not purchased are
to be returned in the name of a person other than the person(s) signing this
Letter of Transmittal or if the check or any Share Certificates not tendered or
not purchased are to be mailed to someone other than the person(s) signing this
Letter of Transmittal or to the person(s) signing this Letter of Transmittal at
an address other than that shown above, the appropriate boxes on this Letter of
Transmittal should be completed. Persons tendering Shares by book-entry transfer
may request that Shares not purchased be credited to such account at the
Book-Entry Transfer Facility. If no such instructions are given, any such Shares
not purchased will be returned by crediting the account at the Book-Entry
Transfer Facility.
 
     8.  Substitute Form W-9.  The tendering holder of Shares is required to
provide the Depositary with such holder's correct taxpayer identification number
("TIN") on Substitute Form W-9, which is provided below, unless an exemption
applies. In the case of such a holder who has completed the box entitled
"Special Payment Instructions" above, however, the correct TIN or Substitute
Form W-9 should be provided for the recipient of the payment pursuant to such
instructions. Failure to provide the information on the Substitute Form W-9 may
subject the tendering holder of Shares to a $50 penalty and to 31% federal
income tax backup withholding on the payment of the purchase price for the
Shares.
<PAGE>   9
 
     9.  Questions and Requests for Assistance or Additional Copies.  Questions
and requests for assistance may be directed to the Information Agent or the
Dealer-Manager at their respective addresses and telephone numbers set forth on
the back cover of the Offer to Purchase and the Supplement. Additional copies of
the Offer to Purchase, the Supplement, the Letter of Transmittal, the Notice of
Guaranteed Delivery and other related materials may be obtained from the
Information Agent or from brokers, dealers, commercial banks and trust
companies.
 
     10.  Lost, Destroyed or Stolen Certificates.  If any Share Certificate(s)
evidencing Shares has been lost, destroyed or stolen, the stockholder should
promptly notify the Depositary. The stockholder will then be instructed as to
the steps that must be taken in order to replace the Share Certificate(s). This
Letter of Transmittal and related documents cannot be processed until the
procedures for replacing lost or destroyed certificates have been followed.
 
     THIS LETTER OF TRANSMITTAL (OR A MANUALLY SIGNED FACSIMILE HEREOF),
TOGETHER WITH SHARE CERTIFICATES OR CONFIRMATION OF BOOK-ENTRY TRANSFER AND ALL
OTHER REQUIRED DOCUMENTS OR NOTICE OF GUARANTEED DELIVERY MUST BE RECEIVED BY
THE DEPOSITARY, ON OR PRIOR TO THE EXPIRATION DATE (AS DEFINED IN THE
SUPPLEMENT).
 
                           IMPORTANT TAX INFORMATION
 
     Under the federal income tax law, a holder of Shares whose tendered Shares
are accepted for payment is required to provide the Depositary (as payer) with
such holder's correct TIN on Substitute Form W-9 below. The holder of Shares
must also state that (i) such holder has not been notified by the Internal
Revenue Service that such holder is subject to backup withholding as a result of
a failure to report all interest or dividends or (ii) the Internal Revenue
Service has notified such holder that such holder is no longer subject to backup
withholding. If the Depositary is not provided with the correct TIN, the
shareholder may be subject to a $50 penalty imposed by the Internal Revenue
Service and payments that are made to such holder may be subject to backup
withholding.
 
     Certain holders of shares (including, among others, all corporations and
certain foreign individuals) are not subject to these backup withholding and
reporting requirements. In order for a foreign individual to qualify as an
exempt recipient, such individual must submit a statement, signed under
penalties of perjury, attesting to such individual's exempt status. Forms of
such statements can be obtained from the Depositary. See the enclosed Guidelines
for Certification of Taxpayer Identification Number on Substitute Form W-9 for
additional instructions.
 
     If backup withholding applies, the Depositary is required to withhold 31%
of any payments made to the holder of shares. Backup withholding is not an
additional tax. Rather, the tax withheld pursuant to backup withholding rules
will be available as a credit against such holder's tax liabilities from the
Internal Revenue Service. If withholding results in an overpayment of taxes, a
refund may be obtained from the Internal Revenue Service.
 
                       WHAT NUMBER TO GIVE THE DEPOSITARY
 
     If the holder of Shares is an individual, the correct TIN is his or her
social security number. In other cases, the correct TIN may be the employer
identification number of the record holder of the Shares tendered hereby. If the
Shares are in more than one name or are not in the name of the actual owner,
consult the enclosed Guidelines for Certification of Taxpayer Identification
Number on Substitute Form W-9 for additional guidance on which number to report.
If the tendering holder of Shares has not been issued a TIN and has applied for
a number or intends to apply for a number in the near future, the holder should
write "Applied For" in the space provided for the TIN in Part I, and sign and
date the Substitute Form W-9. If "Applied For" is written in Part I and the
Depositary is not provided with a TIN within 30 days, the Depositary may
withhold 31% of all payments of the purchase price to such holder until a TIN is
provided to the Depositary.
<PAGE>   10
 
<TABLE>
<S>                          <C>                                                      <C>
 
- ------------------------------------------------------------------------------------------------------------------------
PAYER'S NAME: BANKBOSTON, N.A.
- ------------------------------------------------------------------------------------------------------------------------
 
  SUBSTITUTE                   PART I--PLEASE PROVIDE YOUR TIN IN THE BOX AT RIGHT     -------------------------------
  FORMW-9                      AND CERTIFY BY SIGNING AND DATING BELOW.                     Social Security Number
                                                                                                      OR
                                                                                       -------------------------------
                                                                                        Employer Identification Number
                                                                                       (If awaiting TIN write "Applied
                                                                                                    For")
                             -------------------------------------------------------------------------------------------
 
 Department of the
  Treasury
  Internal Revenue             PART II--For Payees exempt from backup withholding, see the enclosed Guidelines for
  Service                      Certification of Taxpayer Identification Number on Substitute Form W-9 and complete as
  PAYER'S REQUEST FOR          instructed therein.
  TAXPAYER IDENTIFICATION
  NUMBER (TIN) AND             CERTIFICATION--Under penalties of perjury, I certify that:
  CERTIFICATION
                               (1) The number shown on this form is my correct Taxpayer Identification Number (or a
                               Taxpayer Identification Number has not been issued to me and either (a) I have mailed or
                               delivered an application to receive a Taxpayer Identification Number to the appropriate
                               Internal Revenue Service ("IRS") or Social Security administration office or (b) I intend
                               to mail or deliver an application in the near future. I understand that if I do not
                               provide a Taxpayer Identification Number within thirty (30) days, 31% of all reportable
                               payments made to me hereafter will be withheld until I provide a number), and
                               (2) I am not subject to backup withholding because (a) I am exempt from backup
                                   withholding, (b) I have not been notified by the IRS that I am subject to backup
                                   withholding as a result of failure to report all interest or dividends or (c) the IRS
                                   has notified me that I am no longer subject to backup withholding.
                               -----------------------------------------------------------------------------------------
                               CERTIFICATION INSTRUCTIONS--You must cross out item (2) above if you have been notified
                               by the IRS that you are subject to backup withholding because of under reporting interest
                               or dividends on your tax return. However, if after being notified by the IRS that you
                               were subject to backup withholding you received another notification from the IRS that
                               you are no longer subject to backup withholding, do not cross out item (2). (Also see
                               instructions in the enclosed Guidelines.)
                             -----------------------------------------------------------------------------------------
                               SIGNATURE:-------------------------------------------
                               DATE:-----------------------
- ------------------------------------------------------------------------------------------------------------------------
</TABLE>
 
NOTE: FAILURE TO COMPLETE AND RETURN THE SUBSTITUTE FORM W-9 MAY RESULT IN
      BACKUP WITHHOLDING OF 31% OF ANY PAYMENTS MADE TO YOU PURSUANT TO THE
      OFFER TO PURCHASE. PLEASE REVIEW THE ENCLOSED GUIDELINES FOR CERTIFICATION
      OF TAXPAYER IDENTIFICATION NUMBER ON SUBSTITUTE FORM W-9 FOR ADDITIONAL
      DETAILS.
 
      YOU MUST COMPLETE THE FOLLOWING CERTIFICATE IF YOU ARE AWAITING (OR WILL
      SOON APPLY FOR) A TAXPAYER IDENTIFICATION NUMBER
 
             CERTIFICATE OF AWAITING TAXPAYER IDENTIFICATION NUMBER
 
I certify under penalties of perjury that a taxpayer identification number has
not been issued to me, and either (1) I have mailed or delivered an application
to receive a taxpayer identification number to the appropriate Internal Revenue
Service Center or Social Security Administration Office or (2) I intend to mail
or deliver an application in the near future. I understand that if I do not
provide a taxpayer identification number within thirty (30) days, 31% of all
reportable payments made to me will be withheld.

Signature                                        Date 
- ------------------------------------------------ ---------------------------
<PAGE>   11
 
     If you have any questions regarding the Offer, please contact the
Information Agent or the Dealer Manager.
 
                    The Information Agent for the Offer is:
 
                                [MACKENZIE LOGO]
 
                                156 Fifth Avenue
                            New York, New York 10010
                         (212) 929-5500 (Call Collect)
                                       or
                         CALL TOLL-FREE (800) 322-2885
 
                      The Dealer Manager for the Offer is:
                              MERRILL LYNCH & CO.
                             World Financial Center
                                  North Tower
                         New York, New York 10281-1314
                         (212) 449-8971 (Call Collect)

<PAGE>   1
 
                         NOTICE OF GUARANTEED DELIVERY
                                      FOR
                        TENDER OF SHARES OF COMMON STOCK
 
                                       OF
 
                            LIFE TECHNOLOGIES, INC.
                                       TO
 
                       DEXTER ACQUISITION DELAWARE, INC.
                          A WHOLLY-OWNED SUBSIDIARY OF
 
                               DEXTER CORPORATION
                   (NOT TO BE USED FOR SIGNATURE GUARANTEES)
 
         THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT,
NEW YORK CITY TIME, ON TUESDAY, DECEMBER 22, 1998, UNLESS THE OFFER IS EXTENDED.
 
     This Notice of Guaranteed Delivery, or one substantially in the form
hereof, must be used to accept the Offer (as defined below) if certificates
evidencing shares of common stock, par value $0.01 per share (the "Shares"), of
Life Technologies, Inc., a Delaware corporation (the "Company"), are not
immediately available, or if the procedure for book-entry transfer cannot be
completed on a timely basis or if time will not permit all required documents to
reach the Depositary on or prior to the Expiration Date (as defined in the
Supplement (as defined below)). Such form may be delivered by hand or facsimile
transmission or mail to the Depositary. See the sections entitled "THE TENDER
OFFER -- Procedure for Tendering Shares" of the Offer to Purchase (as defined
below) and "THE AMENDED OFFER -- Procedure for Tendering Shares" of the
Supplement.
 
                        The Depositary for the Offer is:
 
                                BANKBOSTON, N.A.
 
<TABLE>
<S>                                <C>                                <C>
             By Mail:                           By Hand:                    By Overnight Delivery:
 
         BankBoston, N.A.           Securities Transfer & Reporting            BankBoston, N.A.
          P.O. Box 9573                      Services, Inc.                  40 Campanelli Drive
 Boston, Massachusetts 02205-9573      c/o Boston EquiServe L.P.        Braintree, Massachusetts 02184
       Attention: Corporate               100 Williams Street                Attention: Corporate
           Reorganization                       Galleria                        Reorganization
                                        New York, New York 10038
                                          Attention: Corporate
                                             Reorganization
</TABLE>
 
                           By Facsimile Transmission:
                          (Eligible Institutions Only)
                                 (781) 794-6333
 
                           Confirm Fax by Telephone:
                                 (781) 794-6388
 
     DELIVERY OF THIS NOTICE OF GUARANTEED DELIVERY TO AN ADDRESS, OR
TRANSMISSION OF INSTRUCTIONS VIA FACSIMILE, OTHER THAN AS SET FORTH ABOVE WILL
NOT CONSTITUTE A VALID DELIVERY TO THE DEPOSITARY.
 
     THIS NOTICE OF GUARANTEED DELIVERY IS NOT TO BE USED TO GUARANTEE
SIGNATURES. IF A SIGNATURE ON A LETTER OF TRANSMITTAL IS REQUIRED TO BE
GUARANTEED BY AN "ELIGIBLE INSTITUTION" UNDER THE INSTRUCTION THERETO, SUCH
SIGNATURE GUARANTEE MUST APPEAR IN THE APPLICABLE SPACE PROVIDED IN THE
SIGNATURE BOX ON THE LETTER OF TRANSMITTAL.
<PAGE>   2
 
Ladies and Gentlemen:
 
     The undersigned hereby tenders to Dexter Acquisition Delaware, Inc., a
Delaware corporation (the "Purchaser") and a wholly-owned subsidiary of Dexter
Corporation, a Connecticut corporation, upon the terms and subject to the
conditions set forth in the Offer to Purchase dated November 2, 1998 (the "Offer
to Purchase"), the Supplement to the Offer to Purchase dated December 7, 1998
(the "Supplement") and the related revised Letter of Transmittal (which, as
amended and supplemented from time to time, together constitute the "Offer"),
receipt of which are hereby acknowledged, the number of Shares specified below
pursuant to the guaranteed delivery procedures described in the sections
entitled "THE TENDER OFFER -- Procedure for Tendering Shares" of the Offer to
Purchase and "THE AMENDED OFFER -- Procedure for Tendering Shares" of the
Supplement.
 
 Number of Shares Tendered:
 ---------------------------
 
 Certificate No(s). (if available):
 
 -----------------------------------------------------------
 
 -----------------------------------------------------------
 
 -----------------------------------------------------------
 
 Account Number at The Depository Trust Company:
 
 -----------------------------------------------------------
 
 Dated:
 ---------------------------------------------------
Name(s) of Holder(s) (Please Type or Print):
 
- -----------------------------------------------------------
 
- -----------------------------------------------------------
 
Address(es) (incl. Zip Code):
 
- -----------------------------------------------------------
 
- -----------------------------------------------------------
 
Area Code and Telephone No.:
- -------------------------
 
Signature(s) of Holder(s):
- ------------------------------
 
- -----------------------------------------------------------
 
                                   GUARANTEE
                    (NOT TO BE USED FOR SIGNATURE GUARANTEE)
 
      The undersigned, a bank, broker, dealer, credit union, savings
 association or other entity which is a member in good standing of the
 Securities Transfer Agents Medallion Program or a bank, broker, dealer, credit
 union, savings association or other entity which is an "eligible guarantor
 institution," as such term is defined in Rule 17Ad-15 under the Securities
 Exchange Act of 1934, as amended, guarantees the delivery to the Depositary of
 the Shares tendered hereby, together with a properly completed and duly
 executed Letter of Transmittal (or manually signed facsimile(s) thereof) and
 any other required documents, or an Agent's Message (as defined in the Offer
 to Purchase) in the case of a book-entry delivery of Shares, all within three
 NASDAQ trading days of the date hereof.
 
      The Eligible Institution that completes this form must communicate the
 guarantee to the Depositary and must deliver the Letter of Transmittal and
 certificates representing Shares to the Depositary within the time period
 shown herein. Failure to do so could result in a financial loss to such
 Eligible Institution.
 
 -----------------------------------------------------
                                  Name of Firm
 
 -----------------------------------------------------
                                     Address
 
 -----------------------------------------------------
                                   City, State
 
 -----------------------------------------------------
                                    Zip Code
 
 -----------------------------------------------------
                             Area Code and Tel. No.
 -----------------------------------------------------
                              Authorized Signature
 
 -----------------------------------------------------
                                      Title
 
 Name:   -----------------------------------------------------
                                  Please Type or Print
 
Dated:
- ----------------------------------------------
 
             NOTE: DO NOT SEND SHARE CERTIFICATES WITH THIS NOTICE.
       SHARE CERTIFICATES SHOULD BE SENT WITH YOUR LETTER OF TRANSMITTAL.

<PAGE>   1


Contact:        
                                                          Dexter Corporation
                                                          One Elm Street
Investors                           Media                 Windsor Locks
                                                          Connecticut 06096-2334
Kathleen Burdett                    Michael Freitag       T: 860.292.7675
John D. Thompson                    Mark Semer            F: 860.292.7627
Dexter Corporation                  Kekst & Company
860.292.7675                        212.521.4800
    or
Mark Harnett
MacKenzie Partners, Inc.
212.929.5877
                                                   
For Immediate Release
                                                   
                                                   
                                                   
DEXTER INCREASES OFFER FOR LIFE TECHNOLOGIES, ELIMINATES MINIMUM SHARE CONDITION
- --------------------------------------------------------------------------------

WINDSOR LOCKS, CONNECTICUT, December 7, 1998 -- Dexter Corporation (NYSE:DEX)
announced today a revised offer to acquire all of the shares of Life
Technologies, Inc. (NASDAQ:LTEK), that Dexter does not presently own. Dexter is
now offering to purchase all such shares for $39.125 per share in cash, net to
the seller without interest thereon, an increase over the original price of
$37.00 per share.

In addition, Dexter announced that it has eliminated the minimum share condition
to the offer and therefore any and all shares properly tendered and not
withdrawn will be purchased. The offer is not subject to financing, which has
been arranged, but remains subject to other conditions set forth in the Offer to
Purchase which remain unchanged.

Tendering shareholders will be entitled to receive the Life Technologies, Inc. 
dividend of $.05 per share payable on January 15, 1999 to all shareholders of 
record on December 18, 1998 which was declared on November 10, 1998.

Dexter also announced that it has extended the expiration of the offer until
12:00 midnight, New York City time, on Tuesday, December 22, 1998. Dexter does
not intend to further extend or amend the offer.

                                    - more -




<PAGE>   2
K. Grahame Walker, Chairman and Chief Executive Officer of Dexter Corporation,
said, "We intend to buy any and all shares tendered at this increased offer
price of $39.125 per share. We believe that Life Technologies, Inc.
shareholders will tender so that they can promptly realize the full and fair
value being offered today." 

Dexter reported that, based on information provided by the depositary for the
offer, as of 12:00 midnight on Friday, December 4, 1998, approximately 2,255,412
shares of Life Technologies, Inc. common stock had been tendered and not
withdrawn. Such number of shares represents approximately 9.5% of the
outstanding Life Technologies, Inc. shares. Dexter currently owns 51.5% of the
outstanding Life Technologies, Inc. shares.
         
Dexter Corporation is a global specialty materials supplier with three operating
segments: specialty polymers, nonwovens, and a majority ownership in Life
Technologies. The company supplies specialty materials to the aerospace,
electronics, food packaging and medical markets.

                      Special Materials for Special Effects

                                     ####



<PAGE>   1
                                                                  EXHIBIT (b)(2)

     [LETTERHEAD OF FRANK L. GROSSMAN, FIRST CHICAGO CAPITAL MARKETS, INC.]



                                                                December 5, 1998



Dexter Corporation
One Elm Street
Windsor Locks, CT 06096-2334

Attention:  Ms. Kathleen Burdett
            Vice President and
            Chief Financial Officer

Gentlemen/Ladies:

Dexter Corporation (the "Borrower"), The First National Bank of Chicago (the
"Agent") and First Chicago Capital Markets, Inc. (the "Arranger") are party to a
certain commitment letter (as amended, the "Commitment Letter"), dated July 6,
1998. The commitment Letter relates to proposed Credit Facilities aggregating
$600,000,000 (the "Facilities") to be used by Dexter for various corporate
purposes, including the financing of the acquisition of Life Technologies, Inc.

In order to accommodate certain potential changes in the transactions
contemplated by the Commitment Letter, the Borrower has asked the Agent and the
Arranger to agree to certain amendments to the Term Sheet (as defined in the
Commitment Letter) and to seek the consent to such amendments of the Lenders
which have previously committed to participate in the Facilities. Subject to the
following sentence, upon the acceptance of this letter by the Borrower, the Term
Sheet shall be amended as set forth on Exhibit A to this letter. Notwithstanding
the foregoing, the Term Sheet shall not be amended, and this letter shall be
without effect, unless and until such time as the Exhibit A changes to the Term
Sheet have also been agreed to by Lenders that have previously committed an
aggregate amount of not less than $600 million to the Facilities.

Except as provided herein, the Commitment Letter and Term Sheet shall be
unmodified and remain in full force and effect.
<PAGE>   2
Please sign and return the acceptance copy of this letter to the Agent to
evidence your agreement herewith. The proposed amendment shall not become
effective unless the Borrower has accepted this letter on or prior to December
10, 1998.

                                            Yours truly,

                                            The First National Bank of Chicago


                                            By: /s/ Frank L. Grossman
                                                -------------------------------
                                                Title: First Vice President


                                            First Chicago Capital Markets, Inc.


                                            By: /s/ Frank L. Grossman
                                                -------------------------------
                                                Title: Managing Director


Accepted and Agreed:
Dexter Corporation


By: /s/ Kathleen Burdett
    -------------------------------------------------
    Title: Vice President and Chief Financial Officer


Date: 12/6/98
      -------------------------------------------
<PAGE>   3
                                    EXHIBIT A

                  The condition set forth under "Acquisition" is hereby amended
by deleting the requirement that, after giving effect to the consummation of the
offer to purchase, the Borrower will not own less than 80% of the shares of each
outstanding class of equity securities of the Target. As a result of such
Amendment, the language under the heading "The Credit Agreement: -Conditions
Precedent: -Acquisition" is hereby amended and restated as follows:

                  Acquisition:      The material terms and conditions of the
                                    offer to purchase pursuant to which the
                                    Acquisition is to be effected, including
                                    without limitation the consideration for and
                                    structure of the Acquisition, shall be
                                    reasonably acceptable to the Agent, and the
                                    conditions therein shall have been satisfied
                                    (or waived with the consent of the Agent,
                                    which consent shall not be unreasonably
                                    withheld). There shall exist no legal or
                                    practical impediment to the consummation of
                                    a merger (other than receipt of the
                                    requisite number of votes of LTI
                                    shareholders sufficient to consummate such
                                    merger).


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