UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549


                                  SCHEDULE 13G
                                 (RULE 13d-102)

             INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT
           TO RULES 13d-1(b), (c) AND (d) AND AMENDMENTS THERETO FILED
                            PURSUANT TO RULE 13d-2(b)
                               (AMENDMENT NO. 1)*


                             Gen-Probe Incorporated
                                (Name of Issuer)


                         Common Stock, $0.0001 par value
                         (Title of Class of Securities)


                                    36866T103
                                 (CUSIP Number)



                                December 31, 2002
             (Date of Event which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule
is filed:

       [ ] Rule 13d-1(b)

       [X] Rule 13d-1(c)

       [ ] Rule 13d-1(d)

*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter the
disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 or otherwise subject to the liabilities of that section of the Act but
shall be subject to all other provisions of the Act (however, see the Notes).


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CUSIP NO. 36866T103                   13G                     PAGE 2 OF 4 PAGES
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--------------------------------------------------------------------------------
1.    NAMES OF REPORTING PERSONS
      I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
      Chilton Investment Company, Inc.
      13-3667517
--------------------------------------------------------------------------------
2.    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions)(a)[ ]
                                                                         (b)[X]
--------------------------------------------------------------------------------
3.    SEC USE ONLY

--------------------------------------------------------------------------------
4.    CITIZENSHIP OR PLACE OF ORGANIZATION
      State of Delaware
--------------------------------------------------------------------------------
              5.     SOLE VOTING POWER
  NUMBER OF          2,256,600
   SHARES     ------------------------------------------------------------------
BENEFICIALLY  6.     SHARED VOTING POWER
  OWNED BY           0
    EACH      ------------------------------------------------------------------
  REPORTING   7.     SOLE DISPOSITIVE POWER
   PERSON             2,256,600
    WITH      ------------------------------------------------------------------
              8.     SHARED DISPOSITIVE POWER
                     0
--------------------------------------------------------------------------------
9.    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
      2,256,600
--------------------------------------------------------------------------------
10.   CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (See
      Instructions)                                                         [ ]
--------------------------------------------------------------------------------
11.   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
       9.5%
--------------------------------------------------------------------------------
12.   TYPE OF REPORTING PERSON (See Instructions)
      CO
--------------------------------------------------------------------------------


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CUSIP NO. 36866T103                   13G                     PAGE 3 OF 4 PAGES
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Pursuant to Rule 13d-2(b) of Regulation 13D-G under the Securities Exchange Act
of 1934, as amended, the Schedule 13G initially filed on October 21, 2002 (the
"Schedule 13G") by Chilton Investment Company, Inc. (the "Reporting Person"),
with respect to the common stock, $0.0001 par value (the "Common Stock") of
Gen-Probe Incorporated, a California corporation, is hereby amended by this
Amendment No. 1 to the Schedule 13G to report a change in beneficial ownership.
The Schedule 13G is hereby amended as follows:

Item 4 is hereby amended and restated in its entirety to read:


ITEM 4.            OWNERSHIP.

                   (a)   Amount beneficially owned: 2,256,600 shares

                   (b)   Percent of class: 9.5%

                   (c)   Number of shares as to which the person has:

                         (i)   Sole power to vote or to direct the
                               vote: 2,256,600
                         (ii)  Shared power to vote or to direct the vote: 0
                         (iii) Sole power to dispose or to direct the
                               disposition of: 2,256,600
                         (iv)  Shared power to dispose or to direct the
                               disposition of: 0



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CUSIP NO. 36866T103                   13G                     PAGE 4 OF 4 PAGES
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                                    SIGNATURE

            After reasonable 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.

Date: February 14, 2003


                                        CHILTON INVESTMENT COMPANY, INC.



                                    By:    /s/ Patricia Mallon
                                        ---------------------------------------
                                        Name:  Patricia Mallon
                                        Title: Managing Director