<PAGE>   1

EXHIBIT 4.2

NEITHER THESE SECURITIES NOR THE SECURITIES ISSUABLE UPON EXERCISE HAVE BEEN
REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR ANY APPLICABLE STATE
SECURITIES LAWS. SUCH SECURITIES MAY NOT BE SOLD, OFFERED FOR SALE, PLEDGED OR
HYPOTHECATED IN THE ABSENCE OF A REGISTRATION STATEMENT IN EFFECT WITH RESPECT
TO THE SECURITIES UNDER SUCH ACT OR AN OPINION OF COUNSEL SATISFACTORY TO THE
COMPANY THAT SUCH REGISTRATION IS NOT REQUIRED OR UNLESS SOLD PURSUANT TO RULE
144 OF SUCH ACT. ANY SUCH TRANSFER MAY ALSO BE SUBJECT TO APPLICABLE STATE
SECURITIES LAWS.


                             GENOMETRIX INCORPORATED
                                     WARRANT

         FOR VALUE RECEIVED, GENOMETRIX INCORPORATED, a Delaware corporation
(the "Company"), hereby certifies that ______________ (the "Holder", which term
shall include any subsequent holder hereof) is entitled to purchase from the
Company fully paid and nonassessable shares (subject to adjustment as provided
below) of the Capital Stock (as defined below), determined as provided herein.

         This Warrant has been issued pursuant to a Note and Warrant Purchase
Agreement of dated as of January 24, 1996 between the Company and the Holder
(the "Agreement"). Hereinafter, (i) "Capital Stock," "Conversion Date",
"Financing" and "Purchase Price" shall have the respective meanings set forth in
the Convertible Note (the "Convertible Note") issued contemporaneously herewith,
and (ii) the shares of Capital Stock purchasable hereunder are referred to as
the "Warrant Shares," (iii) the aggregate purchase price payable for the Warrant
Shares hereunder is referred to as the "Aggregate Warrant Price," and (iv) the
price payable for each of the Warrant Shares hereunder is referred to as the
"Per Share Warrant Price."

         1.       EXERCISE OF WARRANT.

         (a) This Warrant may be exercised, in whole at any time or in part from
time to time by the Holder commencing on the Conversion Date and prior to 5:00
p.m., The Woodlands, Texas time, on the later of (1) [THREE YEARS FROM DATE OF
ISSUE] or (2) the first (1st) anniversary of the Conversion Date, by the
surrender of this Warrant (with the subscription form at the end hereof duly
executed) at the address set forth in Section 8 hereof, together with proper
payment of the Aggregate Warrant Price made by certified or official bank check
payable to the order of the Company.

         (b) This Warrant shall be exercisable for that number of shares as
equals six tenths


                                      -1-

<PAGE>   2

(.6) times the number of shares of Capital Stock determined by dividing (i) the
sum of the outstanding principal amount of the Convertible Note and all accrued
but unpaid interest thereon as of the Conversion Date by (ii) the Purchase Price
per such share of Capital Stock, subject to adjustment as provided herein, and
the Per Share Warrant Price shall be equal to the Purchase Price per share,
subject to adjustment as provided herein.

         (c) If this Warrant is exercised in part, this Warrant must be
exercised for a number of whole shares of the Capital Stock, and the holder is
entitled to receive a new Warrant covering the Warrant Shares as to which this
Warrant has not been exercised. Upon exercise of this Warrant, the Company will
(i) issue a certificate or certificates in the name of the holder for the
largest number of whole shares of the Capital Stock to which the holder shall be
entitled, and (ii) deliver the other securities and properties receivable upon
the exercise of this Warrant.

         2. RESERVATION OF WARRANT SHARES. The Company agrees that, prior to the
expiration of this Warrant, the Company will at all times have authorized and in
reserve, and will keep available, solely for issuance or delivery upon the
exercise of this Warrant, the shares of the Capital Stock and other securities
and properties as from time to time shall be receivable upon the exercise of
this Warrant, free and clear of all restrictions on sale or transfer and free
and clear of all preemptive rights and rights of first refusal.

         3. ADJUSTMENTS OF PER SHARE WARRANT PRICE.

         (a) In case the Company shall, after the Conversion Date (i) pay a
dividend or make a distribution on its Capital Stock in shares of Capital Stock,
(ii) subdivide its outstanding shares of Capital Stock into a greater number of
shares (by a stock split or otherwise), (iii) combine its outstanding shares of
Capital Stock into a smaller number of shares (by a reverse stock split or
otherwise) or (iv) issue by reclassification of its Capital Stock any shares of
capital stock of the Company (whether or not Capital Stock), the Per Share
Warrant Price shall be adjusted so that the holder upon the exercise hereof
shall be entitled to receive the number of shares of Capital Stock or other
capital stock of the Company which it would have owned immediately following
such action had such Warrant been exercised immediately prior thereto. An
adjustment made pursuant to this Section 3(a) shall become effective on the
record date in the case of a dividend or distribution and shall become effective
on the effective date in the case of a subdivision, combination or
reclassification.

         (b) In case of any capital reorganization or reclassification, or any
consolidation or merger to which the Company is a party other than a merger or
consolidation in which the Company is the continuing corporation, or in case of
any sale or conveyance to another entity of the property of the Company as an
entirety or substantially as a entirety, or in the case of any statutory
exchange of securities with another corporation (including any exchange effected
in connection with a merger of a third corporation into the Company) (which
consolidation, merger, sale, conveyance and statutory exchange is referred to
below as a "Sale"), the Holder of this Warrant shall have the right thereafter
to receive on the exercise of this Warrant the kind and


                                      -2-
<PAGE>   3

amount of securities, cash or other property which the Holder would have owned
or have been entitled to receive immediately after such reorganization or
reclassification (as if such transaction had already occurred for the Purchase
Price contemplated in such reorganization or reclassification as the value
attributable to each share of Common Stock by the Company's Board of Directors
in the reorganization or reclassification approved thereby) or Sale had this
Warrant been exercised immediately prior to the effective date of such
reorganization, reclassification or Sale and in any such case, if necessary,
appropriate adjustment shall be made in the application of the provisions set
forth in this Section 3 with respect to the rights and interests thereafter of
the Holder of this Warrant to the end that the provisions set forth in this
Section 3 shall thereafter correspondingly be made applicable, as nearly as may
reasonably be, in relation to any shares of stock or other securities or
property thereafter deliverable on the exercise of this Warrant. The above
provisions of this Section 3(b) shall similarly apply to successive
reorganizations, reclassifications or Sales. The issuer of any shares of stock
or other securities or property thereafter deliverable on the exercise of this
Warrant shall be responsible for all of the agreements and obligations of the
Company hereunder. Notice of any such reorganization, reclassification or Sale
and of said provisions so proposed to be made, shall be mailed to the Holder not
less than thirty (30) days prior to such event. In the event of an anticipated
Sale, the Company or the entity assuming the obligations of the Company
hereunder may (i) upon written notice to the Holder, provide that this Warrant
must be exercised, to the extent then exercisable, within thirty (30) days of
the date of such notice, at the end of which period this Warrant shall terminate
(but if and only if such Sale shall be consummated); or (ii) terminate this
Warrant in exchange for a cash payment equal to the excess of the current market
price of the Warrant Shares subject to this Warrant (to the extent then
exercisable) over the Per Share Warrant Price thereof (but if and only if such
Sale shall be consummated).

         (c) If the Board of Directors of the Company shall declare any dividend
or other distribution with respect to any Capital Stock of the Company, the
Company shall mail notice thereof to the Holder not less than fifteen (15) days
prior to the record date fixed for determining stockholders entitled to
participate in such dividend or other distribution.

         (d) If, as a result of an adjustment made pursuant to this Section 3,
the Holder after surrender of this Warrant for exercise shall become entitled to
receive shares of two or more classes of capital stock of the Company, the Board
of Directors (whose determination shall be conclusive and shall be described in
a written notice to the Holder promptly after such adjustment) shall determine
the allocation of the adjusted Per Share Warrant Price between or among shares
or such classes of capital stock.

         4. FULLY PAID STOCK. The Company agrees that the shares of the Capital
Stock represented by each and every certificate for Warrant Shares delivered on
the exercise of this Warrant shall, at the time of such delivery, be validly
issued and outstanding, fully paid and nonassessable, and not subject to
preemptive rights or rights of first refusal, and the Company will take all such
actions as may be necessary to assure that the par value or stated value, if
any, per share of the Capital Stock is at all times equal to or less than the
then Per Share Warrant


                                      -3-
<PAGE>   4

Price.

         5. LOSS, ETC., OF WARRANT. Upon receipt of evidence reasonably to the
Company of the loss, theft, destruction or mutilation of this Warrant, and of
indemnity reasonably satisfactory to the Company, if lost, stolen or destroyed,
and upon surrender and cancellation of this Warrant, if mutilated, the Company
shall execute and deliver to the Holder a new Warrant of like date, tenor and
denomination.

         6. WARRANT HOLDER NOT STOCKHOLDER. Except as otherwise provided herein,
this Warrant does not confer upon the Holder any right to vote or to consent to
or receive notice as a stockholder of the Company, as such, in respect of any
matters whatsoever, or any other rights or liabilities as a stockholder, prior
to the exercise hereof.

         7. COVENANTS OF WARRANT HOLDER. By acceptance of this Warrant, the
Holder is hereby deemed to covenant and agree with the Company:

         (a) that it is acquiring this Warrant as an investment and not with a
view to distribution hereof. The holder of this Warrant or any Warrant Shares
may transfer this Warrant or such Warrant Shares only pursuant to applicable
Federal and state laws. Each registered Holder of this Warrant acknowledges that
this Warrant has not been registered under the Securities Act of 1933, as
amended (or any successor legislation) (the "Securities Act") and agrees not to
sell, pledge, distribute, offer for sale, transfer or otherwise dispose of this
Warrant or any Warrant Shares issued upon its exercise in the absence of (i) an
effective registration statement as to this Warrant or such Warrant Shares under
the Securities Act, or (ii) an opinion of counsel reasonably acceptable to the
Company to the effect that such registration is not, under the circumstances,
required. In addition, in order for any transferee of this Warrant or any
Warrant Shares to receive any of the benefits of this Warrant or the Warrant
Shares, as the case may be, the Company must have received notice of such
transfer, at the address set forth in Section 8 below, in the form of assignment
or partial assignment attached hereto. Any transferee other than pursuant to an
effective registration statement under the Securities Act or pursuant to Rule
144 promulgated under the Securities Act must also covenant and agree that it is
acquiring this Warrant or such Warrant Shares as an investment and not with a
view to distribution hereof or thereof, except in accordance with the Securities
Act and applicable state securities law; and

         (b) it will not sell, transfer or otherwise dispose of any securities
of the Company during the period commencing upon the date upon which the Company
files a registration statement with the Securities and Exchange Commission for
the registration of any securities for sale to the public and terminating on the
180th day following the date on which the Company's registration statement with
respect to its initial public offering is declared effective, except pursuant to
any written registration rights agreement with the Company.

         8. NOTICES. All notices, requests, consents and demands shall be made
in writing and shall be mailed postage prepaid, or delivered by hand, to the
Company or to the Holder


                                      -4-
<PAGE>   5

thereof at their respective addresses set forth below or to such other address
as may be furnished in writing to the other party hereto:

                  If to the Holder:     ------------------
                                        ------------------
                                        ------------------
                                        ------------------

                  If to the Company:    Genometrix Incorporated
                                        3608 Research Forest Drive, Suite B7
                                        The Woodlands, TX 77381
                                        Attention:   Mitchell D. Eggers
                                                     President

All notices, requests, consents and other communications hereunder shall be
deemed to have been given either (i) if by hand, at the time of the delivery
thereof to the receiving party at the address of such party set forth above,
(ii) if made by telex, telecopy or facsimile transmission, at the time that
receipt thereof has been acknowledged by electronic confirmation or otherwise,
(iii) if sent by overnight courier,on the next business day following the day
such notice is delivered to the courier service, or (iv) if sent by registered
or certified mail, on the 5th business day following the day such mailing is
made.

         9. HEADINGS. The headings of this Warrant have been inserted as a
matter of convenience and shall not affect the construction hereof.

         10. APPLICABLE LAW. This Warrant shall be governed by and construed in
accordance with the law of the State of Texas without giving effect to the
principles of conflicts of law thereof.

         11. AMENDMENT. The terms of this Warrant may be amended or modified or
waiver of compliance of any term hereof may be obtained only in a writing signed
by the Company and the Holder.

                  [Remainder of Page Left Intentionally Blank]


                                      -5-
<PAGE>   6



                  IN WITNESS WHEREOF, the Company has caused this Warrant to be
signed by its President and its corporate seal to be hereunto affixed and
attested by its Secretary effective as of ________________.


                                       GENOMETRIX INCORPORATED



                                       By:
                                          --------------------------------------
                                          Mitchell D. Eggers
                                          President

ATTEST:



---------------------------------
         Secretary

[Corporate Seal]




                                      -6-


<PAGE>   7


                                  SUBSCRIPTION

         The undersigned, ___________________, pursuant to the provisions of the
foregoing Warrant, hereby agrees to subscribe for and purchase
____________________ shares (the "Warrant Shares") of ___________, $.__ par
value per share, of Genometrix Incorporated covered by said Warrant, and makes
payment therefor in full at the price per share provided by said Warrant.

         (a) The undersigned represents that the address of the undersigned
furnished below is the undersigned's principal business address.

         (b) The undersigned (i) was not formed for the purpose of investing in
the Company, (ii) is acquiring the Warrant Shares for its own account for
investment and not with a view to or for resale in connection with any
distribution or resale of the Warrant Shares except in accordance with the
Securities Act of 1933, as amended (or any successor statute) (the "Securities
Act") and applicable state securities laws, and (iii) has not offered or sold
any portion of the Warrant Shares and has no present intention of dividing the
Warrant Shares with others or of selling, distributing or otherwise disposing of
any portion of the Warrant Shares either currently or after the passage of a
fixed or determinable period of time or upon the occurrence or non-occurrence of
any predetermined event or circumstance, except in accordance with the
Securities Act and applicable state securities laws.

         (c) The undersigned understands that (i) the sale of the Warrant Shares
has not been registered under the Securities Act or any state securities law in
reliance upon an exemption therefrom for non-public or limited offerings, (ii)
the Warrant Shares must be held indefinitely unless the sale or other transfer
thereof is subsequently registered under the Securities Act or an exemption from
such registration is available at the time, and (iii) the Company has no
obligation to register the Warrant Shares.

         (d) The undersigned understands and agrees that the following
restrictions and limitations are applicable to its purchase and any resales,
pledges, hypothecations or other transfers of the Warrant Shares:

                  (i) The following legend (or a legend in substantially similar
         form) will be placed on any certificate(s) or other document(s)
         evidencing the Warrant Shares, and the undersigned must comply with the
         terms and conditions set forth in such legend prior to any resales,
         pledges, hypothecations or other transfers of the Warrant Shares:

                  "The securities represented by this certificate have not been
                  registered pursuant to the Securities Act of 1933, as amended
                  ("Act"), or any state securities laws, and may not be sold,
                  pledged, hypothecated or otherwise transferred unless (A) the
                  stockholder wishing to transfer such securities provides an
                  opinion of counsel in form and substance reasonably
                  satisfactory to Genometrix Incorporated (the


                                      -7-
<PAGE>   8

                  "Company") stating that the proposed transfer of the Company's
                  securities is exempt from the registration provisions of all
                  applicable federal and state laws; or (B) said securities are
                  registered pursuant to the Act and all applicable state
                  securities laws.

                  (ii) Stop transfer instructions have been or will be placed on
         any certificates or other documents evidencing the Warrant Shares so as
         to restrict the resale, pledge, hypothecation or other transfer thereof
         in accordance with the provisions hereof.

         (e) The undersigned's representations and warranties made herein shall
survive the execution and delivery hereof and of the Warrant Shares.




Dated:                              Signature:
      ------------------                      ----------------------------------

                                    Address:
                                            ------------------------------------





                                      -8-
<PAGE>   9


LIST OF PURCHASERS


PURCHASER                                ISSUE DATE
---------                                ----------

Palmetto Partners, Ltd.                  January 26, 1996

Palmetto Partners, Ltd.                  April 8, 1996

Palmetto Partners, Ltd.                  May 13, 1996

Palmetto Partners, Ltd.                  August 5, 1996

Donald R. Kendall and Dianne S.          January 26, 1996
Kendall, JTWROS

Donald R. Kendall and Dianne S.          April 8, 1996
Kendall, JTWROS

Donald R. Kendall and Dianne S.          May 13, 1996
Kendall, JTWROS

Donald R. Kendall and Dianne S.          August 5, 1996
Kendall, JTWROS




                                      -9-