EXHIBIT 4.5THIRD AMENDMENT TO RIGHTS AGREEMENT     THIS THIRD AMENDMENT TO RIGHTS AGREEMENT (this “Amendment”) is entered into as of October 3,2006 between Gen-Probe Incorporated, a Delaware corporation (the “Company”), and Mellon InvestorServices LLC, a New Jersey limited liability company, as Rights Agent (the “Rights Agent”).Capitalized terms used but not otherwise defined herein shall have the meanings ascribed to them inthe Rights Agreement (as defined below).     WHEREAS, the Company and the Rights Agent previously entered into the Rights Agreement datedas of September 16, 2002 between the Company and the Rights Agent (the “Rights Agreement”), whichwas amended on October 9, 2002 and again on November 20, 2003; and     WHEREAS, pursuant to Section 26 of the Rights Agreement, the Company and the Rights Agent mayfrom time to time supplement or amend any provision of the Rights Agreement in accordance with theterms of such Section 26.     NOW, THEREFORE, in consideration of the foregoing promises and mutual agreements set forth inthis Amendment, the parties hereby amend the Rights Agreement as follows:     1. Amendment to Section 7.1. Section 7.1 of the Rights Agreement is hereby deletedin its entirety and replaced with the following:7.1 Exercise of Rights. Subject to Section 11.1.2 and except as otherwise providedherein, the registered holder of any Right Certificate may exercise the Rightsevidenced thereby in whole or in part at any time after the Distribution Date uponsurrender of the Right Certificate, with the form of election to purchase andcertification on the reverse side thereof duly executed, to the Rights Agent at theoffice of the Rights Agent designated for such purpose, together with payment ofthe aggregate Purchase Price for the total number of one one-hundredths of aPreferred Share (or other securities, cash or other assets) as to which the Rightsare exercised, at or prior to the time (the “Expiration Date”) that is the earliestof (i) the Close of Business on November 30, 2006 (the “Final Expiration Date”),(ii) the time at which the Rights are redeemed as provided in Section 23 (the“Redemption Date”), (iii) the closing of any merger or other acquisitiontransaction involving the Company pursuant to an agreement of the type described inSection 13.3 at which time the Rights are deemed terminated, or (iv) the time atwhich the Rights are exchanged as provided in Section 27.     2. Amendment of Exhibits. The Exhibits to the Rights Agreement shall be amended toreflect the change in the Final Expiration Date from September 12, 2012 to November 30, 2006,including all conforming changes.     3. Effectiveness. This Amendment shall be deemed effective as of the date firstwritten above, as if executed on such date.     4. Governing Law. This Amendment shall be deemed to be a contract under the laws ofthe State of Delaware and for all purposes shall be governed by and construed in accordance withthe laws of such state applicable to contracts to be made and performed entirely within such state.
 

 
     5. Severability. If any provision, covenant or restriction of this Amendment is heldby a court of competent jurisdiction or other authority to be invalid, illegal or unenforceable,the remainder of the terms, provisions, covenants and restrictions of this Amendment shall remainin full force and effect and shall in no way be effected, impaired or invalidated.     6. Counterparts. This Amendment may be executed in any number of counterparts and eachof such counterparts shall for all purposes be deemed to be an original, and all such counterpartstogether constitute but one and the same original.     7. Construction. On and after the date hereof, each reference in the RightsAgreement to the “Agreement” shall mean the Rights Agreement as amended hereby. Except asspecifically amended above, the Rights Agreement shall remain in full force and effect and ishereby ratified and confirmed. The execution, delivery and effectiveness of this Amendment shallnot, except as expressly provided herein, operate as a waiver of any right, power or remedy of anyparty hereto, nor constitute a waiver of any provision of the Rights Agreement.
 

 
     IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be duly executed, as ofthe date first set forth above.       GEN-PROBE INCORPORATED       By: /s/ R. William Bowen          Name: R. William Bowen     Title: Vice President and General Counsel       MELLON INVESTOR SERVICES LLC       By: /s/ James Kirkland          Name: James Kirkland     Title: Assistant Vice President