<PAGE>   1
                                                                     Exhibit 4.4

                             SECOND AMENDMENT TO THE
                  INFORMATION AND REGISTRATION RIGHTS AGREEMENT

               This Second Amendment to the Information and Registration Rights
Agreement, as amended (the "Amendment"), is made as of October 10, 1991, 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 Amendment (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 of the Company's Series D Preferred Stock
and upon conversion of the Company's warrants issued together with the Company's
Series D Preferred Stock (the "Warrants") according to the terms of the
Information and Registration Rights Agreement dated as of October 11, 1990, as
amended by the Amendment to the Information and Registration Rights Agreement
dated as of October 11, 1990 (together, the "Agreement").

               C. The Company and the Investors desire to amend the Agreement to
grant to certain persons acquiring up to 750,000 shares of Series D Preferred
Stock of the Company and Warrants to purchase up to 750,000 shares of the
Company's Common Stock collectively, the "Series D Investors") on or after
October 10, 1991, for a total aggregate consideration of $6.00 per share and
$1.00 per Warrant, or approximately $5,250,000, Registration rights in
accordance with the Agreement.

               THE PARTIES AGREE AS FOLLOWS:

               1. Definitions. The Capitalized terms used in this Amendment
without definition shall have the same meanings as set forth in the Agreement.

               2. Grant of Registration Rights. In accordance with Section 9 of
the Agreement, each of the Series D Investors hereto shall be considered an
Investor for all purposes of the Agreement.

               3. Counterparts. This Amendment 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.

               4. Governing Law. This Amendment 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.

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


<PAGE>   2

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

THE COMPANY:*                              Biosource Genetics Corporation



                                           By: /s/ Kevin J. Ryan
                                              ----------------------------------
                                              Kevin J. Ryan, President


THE INVESTORS:*




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


                                       2