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. 2)*


                             Gen-Probe Incorporated
                                (Name of Issuer)


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


                                    36866T103
                                 (CUSIP Number)



                                December 31, 2003
             (Date of Event which Requires Filing of this Statement)

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

      [X] Rule 13d-1(b)

      [ ] 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

                     1,277,786
  NUMBER OF   ------------------------------------------------------------------
   SHARES     6.     SHARED VOTING POWER
BENEFICIALLY
  OWNED BY           0
    EACH      ------------------------------------------------------------------
  REPORTING   7.     SOLE DISPOSITIVE POWER
   PERSON
    WITH             1,277,786
              ------------------------------------------------------------------
              8.     SHARED DISPOSITIVE POWER

                     0
--------------------------------------------------------------------------------
9.    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

      1,277,786
--------------------------------------------------------------------------------
10.   CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (See
      Instructions)
                                                                            [ ]
--------------------------------------------------------------------------------
11.   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

      2.6%
--------------------------------------------------------------------------------
12.   TYPE OF REPORTING PERSON (See Instructions)

      IA
--------------------------------------------------------------------------------


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CUSIP NO. 36866T103                    13G                     PAGE 3 OF 4 PAGES
-----------------------                                       ------------------

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 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 Delaware corporation (the "Schedule 13G"), as amended by Amendment No. 1 to
the Schedule 13G filed on February 14, 2003, is hereby amended by this Amendment
No. 2 to the Schedule 13G to report a change in the information reported in the
Schedule 13G. Since the Reporting Person no loner owns 5% or more of the Common
stock, this filing constitutes the Reporting Person's final statement on
Schedule 13G with respect to the Common Stock. The Schedule 13G is hereby
amended as follows:

Items 3, 4, 5 and 10 are hereby amended and restated in their entirety to read:


ITEM 3.   IF THIS STATEMENT IS FILED PURSUANT TO RULE 13D-1(B), OR 13D-2(B) OR
          (C), CHECK WHETHER THE PERSON FILING IS A:

    (a) [ ]  Broker or dealer registered under Section 15 of the Exchange Act.

    (b) [ ]  Bank as defined in Section 3(a)(6) of the Exchange Act.

    (c) [ ]  Insurance company as defined in Section 3(a)(19) of the Exchange
             Act.

    (d) [ ]  Investment company registered under Section 8 of the Investment
             Company Act.

    (e) [X]  An investment adviser in accordance with Rule 13d-1(b)(1)(ii)(E);

    (f) [ ]  An employee benefit plan or endowment fund in accordance with Rule
             13d-1(b)(1)(ii)(F);

    (g) [ ]  A parent holding company or control person in accordance with Rule
             13d-1(b)(1)(ii)(G);

    (h) [ ]  A savings association as defined in Section 3(b) of the Federal
             Deposit Insurance Act;

    (i) [ ]  A church plan that is excluded from the definition of an investment
             company under Section 3(c)(14) of the Investment Company Act;

    (j) [ ]  Group, in accordance with Rule 13d-1(b)(1)(ii)(J).

ITEM 4.            OWNERSHIP.

                   (a)   Amount beneficially owned: 1,277,786 shares

                   (b)   Percent of class:   2.6%

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



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

                         (i)   Sole power to vote or to direct
                               the vote:                              1,277,786
                         (ii)  Shared power to vote or to direct
                               the vote:                              0
                         (iii) Sole power to dispose or to direct
                               the disposition of:                    1,277,786
                         (iv)  Shared power to dispose or to direct
                               the disposition of:                    0

ITEM 5.            OWNERSHIP OF FIVE PERCENT OR LESS OF A CLASS.

                   If this statement is being filed to report the fact that as
                   of the date hereof the reporting person has ceased to be the
                   beneficial owner of more than five percent of the class of
                   securities, check the following [X].

ITEM 10.           CERTIFICATIONS.

      By signing below I certify that, to the best of my knowledge and belief,
the securities referred to above were not acquired and are not held for the
purpose of or with the effect of changing or influencing the control of the
issuer of the securities and were not acquired and are not held in connection
with or as a participant in any transaction having that purpose or effect.


                                    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 13, 2004


                                        Chilton Investment Company, Inc.



                                        By:
                                           -------------------------------------
                                           Name: James Steinthal
                                           Title: Senior Vice President