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                                                                     Exhibit 4.2

                 INFORMATION AND REGISTRATION RIGHTS AGREEMENT


               This INFORMATION AND REGISTRATION RIGHTS AGREEMENT (the
"Agreement") is made as of October 11, 1990, by and among Biosource Genetics
Corporation, a California corporation (the "Company") and the persons listed on
the attached Schedule A, including amendments thereto, who become signatories to
this Agreement (collectively, the "Investors").


                                 R E C I T A L S

               A. The Company and the Investors have entered into agreements for
sale by the Company and purchase by the Investors of the Company's Convertible
Securities.

               B. The Company and the Investors desire to provide for the rights
of the Investors with respect to registration of the Shares of common stock (the
"Common Stock") issued upon conversion or exercise of the Company's Convertible
Securities according to the terms of this Agreement.

               THE PARTIES AGREE AS FOLLOWS:

        1. Certain Definitions.

               As used in this Agreement, the following terms shall have the
following respective meanings:

                      (a) "Commission" shall mean the Securities and Exchange
Commission or any other federal agency at the time administering the Securities
Act.

                      (b) "Convertible Securities" shall mean securities of the
Company convertible into or exchangeable for Registrable Securities.

                      (c) "Form S-3" shall mean Form S-3 issued by the
Commission or any substantially similar form then in effect.

                      (d) "Holder" shall mean any holder of outstanding
Registrable Securities which have not been sold to the public, but only if such
holder is an Investor or an assignee or transferee of Registration rights as
permitted by Section 10.

                      (e) "Initiating Holders" shall mean Holders who in the
aggregate hold at least sixty-six and seven tenths percent (66.7%) of the
Registrable Securities ever outstanding.

                      (f) The terms "Register," "Registered" and "Registration"
refer to a registration effected by preparing and filing a registration
statement in compliance with the Securities Act ("Registration Statement"), and
the declaration or ordering of the effectiveness of such Registration Statement.


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                      (g) "Registrable Securities" shall mean all Common Stock
not previously sold to the public issued or issuable upon conversion or exercise
of any of the Company's Convertible Securities purchased by or issued to the
Investors, including Common Stock issued pursuant to stock splits, stock
dividends and similar distributions.

                      (h) "Registration Expenses" shall mean all expenses
incurred by the Company in complying with Sections 3 or 4 of this Agreement,
including, without limitation, all federal and state registration, qualification
and filing fees, printing expenses, fees and disbursements of counsel for the
Company and one special counsel for Holders (if different from the Company),
blue sky fees and expenses, and the expense of any special audits incident to or
required by any such Registration.

                      (i) "Securities Act" shall mean the Securities Act of
1933, as amended, or any similar federal statute, and the rules and regulations
of the Commission thereunder, all as the same shall be in effect at the time.

                      (j) "Selling Expenses" shall mean all underwriting
discounts and selling commissions applicable to the sale of Registrable
Securities pursuant to this Agreement.

        2. Financial Statements and Resorts to Shareholders.

               As long as an Investor is a holder of any Convertible Securities,
the Company will, as soon as practicable after the end of each fiscal year, and
in any event within 120 days thereafter, and as soon as practical at the end of
each fiscal quarter, and in any event within 45 days thereafter, furnish to such
Investor a consolidated balance sheet of the Company and its subsidiaries, if
any, as of the end of such fiscal year or fiscal quarter, and a consolidated
statement of income and a consolidated statement of changes in financial
position of the Company and its subsidiaries, if any, for such fiscal year or
fiscal quarter, prepared in accordance with generally accepted accounting
principles and setting forth in each case in comparative form the figures for
the previous fiscal year or, if such balance sheet and consolidated statements
cover a fiscal quarter, for the same quarter of the prior fiscal year. When such
balance sheet and consolidated statements are as of the end of the fiscal year,
such balance sheet and consolidated statements shall be certified by independent
public accountants of recognized national standing selected by the Company.

        3. Demand Registration.

               3.1 Request for Registration on Form Other Than Form S-3.

                      Subject to the terms of this Agreement, in the event that
the Company shall receive from the Initiating Holders at any time after the
Company's initial public offering of shares of Common Stock under a Registration
Statement a written request that the Company effect any Registration with
respect to all or a part of the Registrable Securities on a form other than Form
S-3 for an offering of at least 20% of the then outstanding Registrable
Securities (or any lesser percent if the reasonably anticipated aggregate
offering price to the public would exceed $5,000,000), the Company shall (i)
promptly give written notice of the proposed Registration to all other Holders
and shall (ii) as soon as practicable, use its best efforts to effect
Registration of the Registrable Securities of any Holder joining in such request
as are specified


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in a written request given within 20 days after written notice from the Company.
The Company shall not be obligated to take any action to effect any such
Registration pursuant to this Section 3.1 (i) within six months of the effective
date of a Registration initiated by the Company, or (ii) after the Company has
effected one such Registration pursuant to this Section 3.1 and such
Registration has been declared effective.

               3.2 Right of Deferral of Registration on Form Other Than Form
S-3.

                      If the Company shall furnish to all Initiating Holders who
joined in the request a certificate signed by the President of the Company
stating that, in the good faith judgment of the Board of Directors of the
Company, it would be seriously detrimental to the Company for any Registration
to be effected as requested under Section 3.1, the Company shall have the right,
exercisable one time only, to defer the filing of a Registration Statement with
respect to such offering for a period of not more than 120 days from delivery of
the request of the Initiating Holders.

               3.3 Request for Registration on Form S-3.

                      Subject to the terms of this Agreement, in the event that
the Company receives from the Initiating Holders a written request that the
Company effect any Registration on Form S-3 (or any successor form to Form S-3
regardless of its designation) at a time when the Company is eligible to
register securities on Form S-3 (or any successor form to Form S-3 regardless of
its designation) for an offering of Registrable Securities, the Company will
promptly give written notice of the proposed Registration to all the Holders and
will as soon as practicable use its best efforts to effect Registration of the
Registrable Securities specified in such request, together with all or such
portion of the Registrable Securities of any Holder joining in such request as
are specified in a written request delivered to the Company within 30 days after
written notice from the Company of the proposed Registration. The Company shall
be obligated to effect no more than two Registrations under this Section 3.3.

               3.4 Registration of Other Securities in Demand Registration.

                      Any Registration Statement filed pursuant to the request
of the Initiating Holders under this Section 3 may, subject to the provisions of
Section 3.5, include securities of the Company other than Registrable
Securities.

               3.5 Underwriting in Demand Registration.

                      3.5.1 Notice of Underwriting.

                             If the Initiating Holders intend to distribute the
Registrable Securities covered by their request by means of an underwriting,
they shall so advise the Company as a part of their request made pursuant to
Section 3.1 or 3.3, and the Company shall include such information in the
written notice referred to in Section 3.1 or 3.3. The right of any Holder to
Registration pursuant to Section 3 shall be conditioned upon such Holder's
agreement to participate in such underwriting and the inclusion of such Holder's
Registrable Securities in the underwriting.


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                      3.5.2 Inclusion of Other Holders in Demand Registration.

                             If the Company, officers or directors of the
Company holding Common Stock or securities other than Registrable Securities or
holders of securities other than Registrable Securities request inclusion in
such Registration, the Initiating Holders, to the extent they deem advisable and
consistent with the goals of such Registration, shall, on behalf of all Holders,
offer to any or all of the Company, such officers or directors and such holders
of securities other than Registrable Securities that such securities other than
Registrable Securities be included in the underwriting and may condition such
offer on the acceptance by such persons of the terms of this Section 3. In the
event, however, that the number of shares so included exceeds the number of
shares of Registrable Securities included by all Holders, such Registration
shall be treated as governed by Section 4 hereof rather than Section 3, and it
shall not count as a Registration for purposes of Section 3.1 hereof.

                      3.5.3 Selection of Underwriter in Demand Registration.

                             The Company shall (together with all Holders
proposing to distribute their securities through such underwriting) enter into
an underwriting agreement with the representative ("Underwriter's
Representative") of the underwriter or underwriters selected for such
underwriting by the Holders of a majority of the Registrable Securities being
registered by the Initiating Holders and agreed to by the Company.

                      3.5.4 Marketing Limitation in Demand Registration.

                             In the event the Underwriter's Representative
advises the Initiating Holders in writing that market factors (including,
without limitation, the aggregate number of shares of Common Stock requested to
be Registered, the general condition of the market, and the status of the
persons proposing to sell securities pursuant to the Registration) require a
limitation of the number of shares to be underwritten, then (i) first the Common
Stock (other than Registrable Securities) held by officers or directors of the
Company, (ii) next the securities other than Registrable Securities, and (iii)
last the securities requested to be registered by the Company, shall be excluded
from such Registration to the extent required by such limitation. If a
limitation of the number of shares is still required, the Initiating Holders
shall so advise all Holders and the number of shares of Registrable Securities
that may be included in the Registration and underwriting shall be allocated
among all Holders in proportion, as nearly as practicable, to the respective
amounts of Registrable Securities entitled to inclusion in such Registration
held by such Holders at the time of filing the Registration Statement. No
Registrable Securities or other securities excluded from the underwriting by
reason of this Section 3.5.4 shall be included in such Registration Statement.

                      3.5.5 Right of Withdrawal in Demand Registration.

                             If any Holder of Registrable Securities, or a
holder of other securities entitled (upon request) to be included in such
Registration, disapproves of the terms of the underwriting, such person may
elect to withdraw therefrom by written notice to the Company, the underwriter
and the Initiating Holders delivered at least ten days prior to the


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effective date of the Registration Statement. The securities so withdrawn shall
also be withdrawn from the Registration Statement.

               3.6 Blue Sky in Demand Registration.

                      In the event of any Registration pursuant to Section 3,
the Company will exercise its reasonable efforts to Register and qualify the
securities covered by the Registration Statement under such other securities or
Blue Sky laws of such jurisdictions (not exceeding 20 at the expense of the
Company) as shall be reasonably appropriate for the distribution of such
securities; provided, however, that (i) the Company shall not be required to
qualify to do business or to file a general consent to service of process in any
such states or jurisdictions, and (ii) notwithstanding anything in this
Agreement to the contrary, in the event any jurisdiction in which the securities
shall be qualified imposes a nonwaivable requirement that expenses incurred in
connection with the qualification of the securities be borne by selling
shareholders, such expenses shall be payable pro rata by selling shareholders.

        4. Piggyback Registration.

               4.1 Notice of Piggyback Registration and Inclusion of Registrable
Securities.

                      Subject to the terms of this Agreement, in the event the
Company decides to Register any of its Common Stock (either for its own account
or the account of a security holder or holders exercising their respective
demand registration rights) on a form that would be suitable for a registration
involving solely Registrable Securities, the Company will: (i) promptly give
each Holder written notice thereof (which shall include a list of the
jurisdictions in which the Company intends to attempt to qualify such securities
under the applicable Blue Sky or other state securities laws) and (ii) include
in such Registration (and any related qualification under Blue Sky laws or other
compliance), and in any underwriting involved therein, all the Registrable
Securities specified in a written request delivered to the Company by any Holder
within 15 days after delivery of such written notice from the Company. The
Company shall not be obligated to include Registrable Securities of any Holders
in more than two Registrations of the Company.

               4.2 Underwriting in Piggyback Registration.

                      4.2.1 Notice of Underwriting in Piggyback Registration.

                             If the Registration of which the Company gives
notice is for a Registered public offering involving an underwriting, the
Company shall so advise the Holders as a part of the written notice given
pursuant to Section 4.1. In such event the right of any Holder to Registration
shall be conditioned upon such underwriting and the inclusion of such Holder's
Registrable Securities in such underwriting to the extent provided in this
Section 4. All Holders proposing to distribute their securities through such
underwriting shall (together with the Company and the other holders distributing
their securities through such underwriting) enter into an underwriting agreement
with the Underwriter's Representative for such offering. The Holders shall have
no right to participate in the selection of the underwriters for an offering
pursuant to this Section 4.


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                      4.2.2 Marketing Limitation in Piggyback Registration.

                             In the event the Underwriter's Representative
advises the Holders seeking registration of Registrable Securities pursuant to
Section 4 in writing that market factors (including, without limitation, the
aggregate number of shares of Common Stock requested to be Registered, the
general condition of the market, and the status of the persons proposing to sell
securities pursuant to the Registration) require a limitation of the number of
shares to be underwritten, the Underwriter's Representative (subject to the
allocation priority set forth in Section 4.2.3) may:

                      (a) in the case of the Company's initial Registered public
offering, exclude some or all Registrable Securities from such registration and
underwriting;

                      (b) in the case of the first Registered public offering
subsequent to the initial public offering, limit the number of shares of
Registrable Securities to be included in such Registration and underwriting to
not more than twenty percent (20%) of the securities included in such
Registration (based on aggregate market values); and

                      (c) in the case of any subsequent registered public
offering, limit the number of shares of Registrable Securities to be included in
such Registration and underwriting to not more than twenty-five percent (25%) of
the securities included in such Registration (based on aggregate market values).

                      4.2.3 Allocation of Shares in Piggyback Registration.

                             In the event that the Underwriter's Representative
limits the number of shares to be included in a Registration pursuant to section
4.2.2, the number of shares to be included in such Registration shall be
allocated (subject to Section 4.2.2) in the following manner: The shares (other
than Registrable Securities) held by officers or directors of the Company shall
be excluded from such registration and underwriting to the extent required by
much limitation. If a limitation of the number of shares is still required after
such exclusion, the number of shares that may be included in the Registration
and underwriting by selling shareholders shall be allocated among all Holders
thereof and other holders of securities other than Registrable Securities
requesting and legally entitled to include shares in such Registration, in
proportion, as nearly as practicable, to the respective amounts of securities
(including Registrable Securities) entitled to inclusion in such Registration
held by such Holders and such other holders at the time of filing of the
Registration Statement. No Registrable Securities or other securities excluded
from the underwriting by reason of this Section 4.2.3 shall be included in the
Registration Statement.

                      4.2.4 Withdrawal in Piggyback Registration.

                             If any Holder disapproves of the terms of any such
underwriting, he may elect to withdraw therefrom by written notice to the
Company and the underwriter delivered at least 14 days prior to the effective
date of the Registration Statement. Any Registrable Securities or other
securities excluded or withdrawn from such underwriting shall be withdrawn from
such Registration.


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               4.3 Blue Sky in Piggyback Registration.

                      In the event of any Registration of Registrable Securities
pursuant to Section 4, the Company will exercise its best efforts to Register
and qualify the securities covered by the Registration Statement under such
other securities or Blue Sky laws of such jurisdictions (not exceeding 20 unless
otherwise agreed to by the Company) as shall be reasonably appropriate for the
distribution of such securities; provided, however, that (i) the Company shall
not be required to qualify to do business or to file a general consent to
service of process in any such states or jurisdictions, and (ii) notwithstanding
anything in this Agreement to the contrary, in the event any jurisdiction in
which the securities shall be qualified imposes a nonwaivable requirement that
expenses incurred in connection with the qualification of the securities be
borne by selling shareholders, such expenses shall be payable pro rata by
selling shareholders.

        5. Expenses of Registration.

               All Registration Expenses incurred in connection with one
Registration pursuant to Section 3 and up to two Registrations pursuant to
Section 4, shall be borne by the Company. All Registration Expenses incurred in
connection with any other Registration, qualification or compliance shall be
apportioned among the Holders and other holders of the securities so registered
on the basis of the number of shares so registered. Notwithstanding the above,
the Company shall not be required to pay for any expenses of any Registration
proceeding begun pursuant to Section 3 if the Registration request is
subsequently withdrawn at the request of the Holders of a majority of the
Registrable Securities to be registered (which Holders shall bear such
expenses), unless the Holders of such majority of the Registrable Securities
agree to forfeit their right to demand registration pursuant to Section 3. All
Selling Expenses shall be borne by the Holders of the securities registered pro
rata on the basis of the number of shares registered.

        6. Registration Procedures.

               The Company will keep each Holder whose Registrable Securities
are included in any registration pursuant to this Agreement advised as to the
initiation and completion of such Registration. At its expense the Company will:
(a) use its best efforts to keep such Registration effective for a period of 90
days or until the Holder or Holders have completed the distribution described in
the Registration Statement relating thereto, whichever first occurs; and (b)
furnish such number of prospectuses (including preliminary prospectuses) and
other documents as a Holder from time to time may reasonably request.

        7. Information Furnished by Holder.

               It shall be a condition precedent of the Company's obligations
under this Agreement that each Holder of Registrable Securities included in any
Registration furnish to the Company such information regarding such Holder and
the distribution proposed by such Holder or Holders as the Company may
reasonably request.


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        8. Indemnification.

               8.1 Company's Indemnification of Holders.

                      To the extent permitted by law, the Company will indemnify
each Holder, each of its officers, directors and constituent partners, legal
counsel for the Holders, and each person controlling such Holder, with respect
to which Registration, qualification or compliance of Registrable Securities has
been effected pursuant to this Agreement, and each underwriter, if any, and each
person who controls any underwriter against all claims, losses, damages or
liabilities (or actions in respect thereof) to the extent such claims, losses,
damages or liabilities arise out of or are based upon any untrue statement (or
alleged untrue statement) of a material fact contained in any prospectus or
other document (including any related Registration Statement) incident to any
such Registration, qualification or compliance, or are based on any omission (or
alleged omission) to state therein a material fact required to be stated therein
or necessary to make the statements therein not misleading, or any violation by
the Company of any rule or regulation promulgated under the Securities Act
applicable to the Company and relating to action or inaction required of the
Company in connection with any such Registration, qualification or compliance;
and the Company will reimburse each such Holder, each such underwriter and each
person who controls any such Holder or underwriter, for any legal and any other
expenses reasonably incurred in connection with investigating or defending any
such claim, loss, damage, liability or action; provided, however, that the
indemnity contained in this Section 8.1 shall not apply to amounts paid in
settlement of any such claim, loss, damage, liability or action if settlement is
effected without the consent of the Company (which consent shall not
unreasonably be withheld); and provided, further, that the Company will not be
liable in any such case to the extent that any such claim, loss, damage,
liability or expense arises out of or is based upon any untrue statement or
omission based upon and in conformity with written information furnished to the
Company by such Holder.

               8.2 Holder's Indemnification of Company.

                      To the extent permitted by law, each Holder will, if
Registrable Securities held by such Holder are included in the securities as to
which such Registration, qualification or compliance is being effected pursuant
to this Agreement, indemnify the Company, each of its directors and officers,
each legal counsel and independent accountant of the Company, each underwriter,
if any, of the Company's securities covered by such a Registration Statement,
each person who controls the Company or such underwriter within the meaning of
the Securities Act, and each other such Holder, each of its officers, directors
and constituent partners and each person controlling such other Holder, against
all claims, losses, damages and liabilities (or actions in respect thereof)
arising out of or based upon any untrue statement (or alleged untrue statement)
of a material fact contained in any such Registration Statement, prospectus,
offering circular or other document, or any omission (or alleged omission) to
state therein a material fact required to be stated therein or necessary to make
the statements therein not misleading, or any violation by such Holder of any
rule or regulation promulgated under the Securities Act applicable to such
Holder and relating to action or inaction required of such Holder in connection
with any such Registration, qualification or compliance; and will reimburse the
Company, such Holders, such directors, officers, partners, persons, law and
accounting firms, underwriters or control persons for any legal and any other
expenses reasonably incurred in connection with


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investigating or defending any such claim, loss, damage, liability or action;
provided, however, that the indemnity contained in this Section 8.2 shall not
apply to amounts paid in settlement of any such claim, loss, damages, liability
or action of settlement as effected without the consent of such Holder (which
consent shall not be unreasonably withheld); and provided, further, that such
Holder shall be liable only to the extent that such untrue statement (or alleged
untrue statement) or omission (or alleged omission) is made in such Registration
Statement, prospectus, offering circular or other document in reliance upon and
in conformity with written information furnished to the Company by such Holder.

               8.3 Indemnification Procedure.

                      Promptly after receipt by an indemnified party under this
Section 8 of notice of the commencement of any action, such indemnified party
will, if a claim in respect thereof is to be made against an indemnifying party
under this Section 8, notify the indemnifying party in writing of the
commencement thereof and generally summarize such action. The indemnifying party
shall have the right to participate in and to assume the defense of such claim;
provided, however, that the indemnifying party shall be entitled to select
counsel for the defense of such claim with the approval of any parties entitled
to indemnification, which approval shall not be unreasonably withheld; provided
further, however, that if either party reasonably determines that there may be a
conflict between the position of the Company and the Investors in conducting the
defense of such action, suit or proceeding by reason of recognized claims for
indemnity under this Section 8, then counsel for such party shall be entitled to
conduct the defense to the extent reasonably determined by such counsel to be
necessary to protect the interest of such party. The failure to notify an
indemnifying party promptly of the commencement of any such action, if
prejudicial to the ability of the indemnifying party to defend such action,
shall relieve such indemnifying party, to the extent so prejudiced, of any
liability to the indemnified party under this Section 8, but the omission so to
notify the indemnifying party will not relieve such party of any liability that
such party may have to any indemnified party otherwise other than under this
Section 8.

        9. Limitations on Registration Rights Granted to Other Securities.

               From and after the date of this Agreement, the Company shall not
enter into any agreement with any holder or prospective holder of any securities
of the Company providing for the granting to such holder of any information or
Registration rights, except that additional holders may be added as parties to
this Agreement with regard to any or all Registrable Securities of the Company
held by them. Any such additional parties shall execute a counterpart of this
Agreement, and upon execution by such additional parties and by the Company,
shall be considered an Investor for all purposes of this Agreement. The
additional parties and the additional Registrable Securities shall be identified
in an amendment to Schedule A hereto.

        10. Transfer of Rights.

               The right to information under Section 2 and to cause the Company
to Register securities granted by the Company to the Investors under this
Agreement may be assigned by any Holder to a transferee or assignee of any
Convertible Securities or Registrable Securities not sold to the public;
provided, however, that (i) the Company must receive written notice prior to


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the time of said transfer, stating the name and address of said transferee or
assignee and identifying the securities with respect to which such information
and Registration rights are being assigned, and (ii) the transferee or assignee
of such rights must not be a person deemed by the Board of Directors of the
Company, in its reasonable judgment, to be a competitor or potential competitor
of the Company.

        11. Market Stand-Off.

               Each Holder hereby agrees that, if so requested by the Company
and the Underwriter's Representative (if any), such Holder shall not sell or
otherwise transfer any Registrable Securities or other securities of the Company
during the 120-day period following the effective date of a Registration
Statement of the Company filed under the Securities Act.

        12. No-Action Letter or opinion of Counsel in Lieu of Registration;
            Conversion of Convertible Securities.

               Notwithstanding anything else in this Agreement, if the Company
shall have obtained from the Commission a "no-action" letter in which the
Commission has indicated that it will take no action if, without Registration
under the Securities Act, any Holder disposes of Registrable Securities covered
by any request for Registration made under this Section in the specific manner
in which such Holder proposes to dispose of the Registrable Securities included
in such request (such as including, without limitation, inclusion of such
Registrable Securities in an underwriting initiated by either the Company or the
holders), or if in the opinion of counsel for the Company concurred in by
counsel for such Holder, which concurrence shall not be unreasonably withheld,
no Registration under the Securities Act is required in connection with such
disposition, the Registrable Securities included in such request shall not be
eligible for Registration under this Agreement; provided, however, that any
Registrable Securities not so disposed of shall be eligible for Registration in
accordance with the terms of this Agreement with respect to other proposed
dispositions to which this Section 12 does not apply. The Registration rights of
the Holders of the Registrable Securities set forth in this Agreement are
conditioned upon the conversion of the Registrable Securities with respect to
which registration is sought into Common Stock prior to the effective date of
the Registration Statement.

        13. Miscellaneous.

               13.1 Entire Agreement; Successors and Assigns.

                      This Agreement constitutes the entire contract between the
Company and the Investors relative to the subject matter hereof. Any previous
agreement between the Company and the Investors concerning information to be
provided to Investors and Registration rights is superseded by this Agreement.
Subject to the exceptions specifically set forth in this Agreement, the terms
and conditions of this Agreement shall inure to the benefit of and be binding
upon the respective executors, administrators, heirs, successors and assigns of
the parties.


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               13.2 Governing Law.

                      This Agreement shall be governed by and construed in
accordance with the laws of the State of California applicable to contracts
entered into and wholly to be performed within the State of California by
California residents.

               13.3 Counterparts.

                      This Agreement may be executed in two or more
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

               13.4 Headings.

                      The headings of the Sections of this Agreement are for
convenience and shall not by themselves determine the interpretation of this
Agreement.

               13.5 Notices.

                      Any notice required or permitted hereunder shall be given
in writing and shall be conclusively deemed effectively given upon personal
delivery, or five days after deposit in the United States mail, by registered or
certified mail, postage prepaid, addressed (i) if to the Company, as set forth
below the Company's name on the signature page of this Agreement, and (ii) if to
an Investor, at such Investor's address as set forth on Schedule A, or at such
other address as the Company or such Investor may designate by 10 days' advance
written notice to the Investors or the Company, respectively.

               13.6 Amendment of Agreement.

                      Any provision of this Agreement may be amended only by a
written instrument signed by the Company and by persons holding at least
sixty-six and seven tenths percent (66.7%) of the Registrable Securities as
defined in Section 1 of this Agreement.


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        IN WITNESS WHEREOF, the parties hereto have executed this Agreement as
of the day and year first above written.

THE COMPANY:*                            Biosource Genetics Corporation



                                         By: /s/ Robert L. Erwin
                                            ------------------------------------
                                            Robert L. Erwin, President


THE INVESTORS:*





* Original signature pages and Schedule A are on file at the offices of the
Company.


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