Exhibit 3.7

                          TRANSKARYOTIC THERAPIES, INC.

                 AMENDMENT NO. 2 TO AMENDED AND RESTATED BY-LAWS



Pursuant to Section 109 of the Delaware Corporate Law, Article II, Section 2 of
the Corporation's Amended and Restated By-Laws is hereby amended and restated in
its entirety as follows:

               "SPECIAL MEETINGS. Special meetings of the Stockholders for any
               purpose may be called at any time by the Board of Directors, the
               Chairman of the Board, or if no Chairman has been elected, by the
               President and Chief Executive Officer, and shall be called by the
               Chairman of the Board or, if none, by the President and Chief
               Executive Officer at the request of the holders of a majority of
               the outstanding shares of capital stock entitled to vote.
               Following receipt of a request by any stockholder or stockholders
               entitled to call a special meeting pursuant to this Section 2,
               the Chairman of the Board or, if none, the President and Chief
               Executive Officer shall determine a date and time for the
               requested meeting, which date shall not be less than 60 days nor
               more than 90 days after receipt of such request, and the Board of
               Directors shall establish a record date for the determination of
               stockholders entitled to vote at such meeting. Following such
               determination and establishment, it shall be the duty of the
               Secretary, or if the Secretary be unable or unwilling, an
               Assistant Secretary, to cause notice of the special meeting to be
               given in accordance with Section 3 of this Article II. Special
               meetings shall be held at such place or places within or without
               the State of Delaware as shall from time to time be designated by
               the Board of Directors and stated in the notice of such meeting.
               At a special meeting no business shall be transacted and no
               corporate action shall be taken other than that stated in the
               notice of the meeting."