Exhibit 3.1
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                                              (As amended through July 24, 2001)

                                    BYLAWS

                                      of

                           GENOME THERAPEUTICS CORP.

                      Section 1. ARTICLES OF ORGANIZATION

     The name and purposes of the corporation shall be as set forth in the
articles of organization. These bylaws, the powers of the corporation and of its
directors and stockholders, or of any class of stockholders if there shall be
more than one class of stock, and all matters concerning the conduct and
regulation of the business and affairs of the corporation shall be subject to
such provisions in regard thereto, if any, as are set forth in the articles of
organization as from time to time in effect.

                            Section 2. STOCKHOLDERS

    2.1.  Annual Meeting. The annual meeting of the stockholders shall be held
at 10:00 A.M. on the third Tuesday in October in each year, unless a different
hour is fixed by the president or the directors. If that day be a legal holiday
at the place where the meeting is to be held, the meeting shall be held on the
next succeeding day not a legal holiday at such place. Purposes for which an
annual meeting is to be held, additional to those prescribed by law, by the
articles of organization or by these bylaws, may be specified by the president
or by the directors.

    2.2.  Special Meeting in Place of Annual Meeting. If no annual meeting has
been held in accordance with the foregoing provisions, a special meeting of the
stockholders may be held in place thereof, and any action taken at such special
meeting shall have the same force and effect as if taken at the annual meeting,
and in such case all references in these bylaws to the annual meeting of the
stockholders shall be deemed to refer to such special meeting. Any such special
meeting shall be called as provided in Section 2.3.

    2.3.  Special Meetings. A special meeting of the stockholders may be called
at any time by the president or by the directors. Each call of a meeting shall
state the place, date, hour and purposes of the meeting.

    2.4.  Place of Meetings. All meetings of the stockholders shall be held at
the principal office of the corporation in Massachusetts or, to the extent
permitted by the articles of organization, at such other place within the United
States as shall be fixed by the president or the directors. Any adjourned
session of any meeting of the stockholders shall be held at the same city or
town as the initial session, or within Massachusetts, in either case at the
place designated in the vote of adjournment.


    2.5.  Notice of Meetings. A written notice of each meeting of stockholders,
stating the place, date and hour and the purposes of the meeting, shall be given
at least seven days before the meeting to each stockholder entitled to vote
thereat and to each stockholder who, by law, by the articles of organization or
by these bylaws, is entitled to notice, by leaving such notice with him or at
his residence or usual place of business, or by mailing it, postage prepaid,
addressed to such stockholder at his address as it appears in the records of the
corporation. Such notice shall be given by the clerk or an assistant clerk or by
an officer designated by the directors. Whenever notice of a meeting is required
to be given to a stockholder under any provision of the Business Corporation Law
of the Commonwealth of Massachusetts or of the articles of organization or these
bylaws, a written waiver thereof, executed before or after the meeting by such
stockholder or his attorney thereunto authorized and filed with the records of
the meeting, shall be deemed equivalent to such notice.

    2.6.  Quorum of Stockholders.  At any meeting of the stockholders, a quorum
shall consist of a majority in interest of all stock issued and outstanding and
entitled to vote at the meeting, except when a larger quorum is required by law,
by the articles of organization or by these bylaws. Stock owned directly or
indirectly by the corporation, if any, shall not be deemed outstanding for this
purpose. Any meeting may be adjourned from time to time by a majority of the
votes properly cast upon the question, whether or not a quorum is present, and
the meeting may be held as adjourned without further notice.

    2.7.  Action by Vote. When a quorum is present at any meeting, a plurality
of the votes properly cast for election to any office shall elect to such
office, and a majority of the votes properly cast upon any question other than
an election to an office shall decide the question, except when a larger vote is
required by law, by the articles of organization or by these bylaws. No ballot
shall be required for any election unless requested by a stockholder present or
represented at the meeting and entitled to vote in the election.

    2.8.  Voting.  Stockholders entitled to vote shall have one vote for each
share of stock entitled to vote held by them of record according to the records
of the corporation, unless otherwise provided by the articles of organization.
The corporation shall not, directly or indirectly, vote any share of its own
stock.  The provisions of Chapter 110D of the Massachusetts General Laws shall
not apply to the Company. The provisions of Chapter 110F of the Massachusetts
General Laws shall not apply to the Company.

    2.9.  Action by Writing. Any action required or permitted to be taken at any
meeting of the stockholders may be taken without a meeting if all stockholders
entitled to vote on the matter consent to the action in writing and the written
consents are filed with the records of the meetings of stockholders. Such
consents shall be treated for all purposes as a vote at a meeting.

    2.10. Proxies. To the extent permitted by law, stockholders entitled to
vote may vote either in person or by proxy. No proxy dated more than six months
before the meeting named therein shall be valid. Unless otherwise specifically
limited by their terms, such proxies shall entitle the holders thereof to vote
at any adjournment of such meeting but shall not be valid after the final
adjournment of such meeting.

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                         Section 3. BOARD OF DIRECTORS

    3.1.  Number. At the annual meeting of stockholders such stockholders as
have the right to vote for the election of directors shall fix the number of
directors at not less than three nor more than nine directors and shall elect
the number of directors so fixed; provided, however, that the number of
directors shall be fixed at not less than two whenever there shall be only two
stockholders and not less than one whenever there shall be only one stockholder.
The number of directors may be increased at any time or from time to time either
by the stockholders or by the directors by vote of a majority of the directors
then in office. The number of directors may be decreased to any number permitted
by law at any time or from time to time either by the stockholders or by the
directors by a vote of a majority of the directors then in office, but only to
eliminate vacancies existing by reason of the death, resignation, removal or
disqualification of one or more directors. No director need be a stockholder.

    3.2.  Tenure. Except as otherwise provided by law, by the articles of
organization or by these bylaws, each director shall hold office until the next
annual meeting of the stockholders and until his successor is duly elected and
qualified, or until he sooner dies, resigns, is removed or becomes disqualified.

    3.3.  Powers. Except as reserved to the stockholders by law, by the articles
of organization or by these bylaws, the business of the corporation shall be
managed by the directors who shall have and may exercise all the powers of the
corporation. In particular, and without limiting the generality of the
foregoing, the directors may at any time issue all or from time to time any part
of the unissued capital stock of the corporation from time to time f authorized
under the articles of organization and may determine, subject to any
requirements of law, the consideration for which stock is to be issued and the
manner i of allocating such consideration between capital and surplus.

    3.4.  Committees. The directors may, by vote of a majority of the directors
then in office, elect from their number an executive committee and other
committees and delegate to any such committee or committees some or all of the
powers of the directors except those which by law, by the articles of
organization or by these bylaws they are prohibited from delegating. Except as
the directors may otherwise determine, any such committee may make rules for the
conduct of its business, but unless otherwise provided by the directors or such
rules, its business shall be conducted as nearly as may be in the same manner as
is provided by these bylaws for the conduct of business by the directors.

    3.5.  Regular Meetings. Regular meetings of the directors may be held
without call or notice at such places and at such times as the directors may
from time to time determine, provided that reasonable notice of the first
regular meeting following any such determination shall be given to absent
directors: A regular meeting of the directors may be held without call or notice
immediately after and at the same place as the annual meeting of the
stockholders.

    3.6.  Special Meetings. Special meetings of the directors may be held at any
time and at any place designated in the call of the meeting, when called by the
chairman of the board, if any,

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the president or the treasurer or by two or more directors, reasonable notice
thereof being given to each director by the secretary or an assistant secretary,
or, if there be none, by the clerk or an assistant clerk, or by the officer or
one of the directors calling the meeting.

    3.7.  Notice. It shall be sufficient notice to a director to send notice by
mail at least forty-eight hours or by telegram at least twenty-four hours before
the meeting addressed to him at his usual or last known business or residence
address or to give notice to him in person or by telephone at least twenty-four
hours before the meeting. Notice of a meeting need not be given to any director
if a written waiver of notice, executed by him before or after the meeting, is
filed with the records of the meeting, or to any director who attends the
meeting without protesting prior thereto or at its commencement the lack of
notice to him. Neither notice of a meeting nor a waiver of a notice need specify
the purposes of the meeting.

    3.8.  Quorum. At any meeting of the directors a majority of the directors
then in office shall constitute a quorum. Any meeting may be adjourned from time
to time by a majority of the votes cast upon the question, whether or not a
quorum is present, and the meeting may be held as adjourned without further
notice.

    3.9.  Action by Vote. When a quorum is present at any meeting, a majority of
the directors present may take any action, except when a larger vote is required
by law, by the articles of organization or by these bylaws.

    3.10. Action by Writing. Unless the articles of organization otherwise
provide, any action required or permitted to be taken at any meeting of the
directors may be taken without a meeting if all the directors consent to the
action in writing and the written consents are filed with the records of the
meetings of the directors. Such consents shall be treated for all purposes as a
vote taken at a meeting.

    3.11. Presence Through Communications Equipment. Unless otherwise provided
by law or the articles of organization, members of the board of directors may
participate in a meeting of such board by means of a conference telephone or
similar communications equipment by means of which all persons participating in
the meeting can hear each other at the same time and participation by such means
shall constitute presence in person at a meeting.

                        Section 4. OFFICERS AND AGENTS

    4.1.  Enumeration; Qualification. The officers of the corporation shall be a
president, a treasurer, a clerk, and such other officers, if any, as the
incorporators at their initial meeting, or the directors from time to time, may
in their discretion elect or appoint. The corporation may also have such agents,
if any, as the incorporators at their initial meeting, or the directors from
time to time, may in their discretion appoint. Any officer may be but none need
be a director or stockholder. The clerk shall be a resident of Massachusetts
unless the corporation has a resident agent appointed for the purpose of service
of process. Any two or more offices may be held by the same person. Any officer
may be required by the directors to give bond for the faithful performance of
his duties to the corporation in such amount and with such sureties as the
directors may determine.

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    4.2.  Powers. Subject to law, to the articles of organization and to the
other provisions of these bylaws, each officer shall have, in addition to the
duties and powers herein set forth, such duties and powers as are commonly
incident to his office and such duties and powers as the directors may from time
to time designate.

    4.3.  Election. The president, the treasurer and the clerk shall be elected
annually by the directors at their first meeting following the annual meeting of
the stockholders. Other officers, if any, may be elected or appointed by the
board of directors at said meeting or at any other time.

    4.4.  Tenure. Except as otherwise provided by law or by the articles of
organization or by these bylaws, the president, the treasurer and the clerk
shall hold office until the first meeting of the directors following the next
annual meeting of the stockholders and until their respective successors are
chosen and qualified, and each other officer shall hold office until the first
meeting of the directors following the next annual meeting of the stockholders
unless a shorter period shall have been specified by the terms of his election
or appointment, or in each case until he sooner dies, resigns, is removed or
becomes disqualified. Each agent shall retain his authority at the pleasure of
the directors.

    4.5.  Chief Executive Officer. The chief executive officer of the
corporation shall be the chairman of the board, if any, the president or such
other officer as is designated by the directors and shall, subject to the
control of the directors, have general charge and supervision of the business of
the corporation and, except as the directors shall otherwise determine, preside
at all meetings of the stockholders and of the directors. If no such designation
is made, the president shall be the chief executive officer.

    4.6.  Chairman of the Board. If a chairman of the board of directors is
elected, he shall have the duties and powers specified in these bylaws and shall
have such other duties and powers as may be determined by the directors.

    4.7.  President and Vice Presidents. The president shall have the duties and
powers specified in these bylaws and shall have such other duties and powers as
may be determined by the directors.

    Any vice presidents shall have such duties and powers as shall be
designated from time to time by the directors.

    4.8.  Treasurer and Assistant Treasurers. Except as the directors shall
otherwise determine, the treasurer shall be the chief financial and accounting
officer of the corporation and shall be in charge of its funds and valuable
papers, books of account and accounting records, and shall have such other
duties and powers as may be designated from time to time by the directors.

    Any assistant treasurers shall have such duties and powers as shall be
designated from time to time by the directors.

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    4.9.  Clerk and Assistant Clerks. The clerk shall record all proceedings of
the stockholders in a book or series of books to be kept therefor, which book or
books shall be kept at the principal office of the corporation or at the office
of its transfer agent or of its clerk and shall be open at all reasonable times
to the inspection of any stockholder. In the absence of the clerk from any
meeting of stockholders, an assistant clerk, or if there be none or he is
absent, a temporary clerk chosen at the meeting, shall record the proceedings
thereof in the aforesaid book. Unless a transfer agent has been appointed the
clerk shall keep or cause to be kept the stock and transfer records of the
corporation, which shall contain the names and record addresses of all
stockholders and the amount of stock held by each. If no secretary is elected,
the clerk shall keep a true record of the proceedings of all meetings of the
directors and in his absence from any such meeting an assistant clerk, or if
there be none or he is absent, a temporary clerk chosen at the meeting, shall
record the proceedings thereof.

    Any assistant clerks shall have such other duties and powers as shall be
designated from time to time by the directors.

    4.10. Secretary and Assistant Secretaries. If a secretary is elected, he
shall keep a true record of the proceedings of all meetings of the directors and
in his absence from any such meeting an assistant secretary, or if there be none
or he is absent, a temporary secretary chosen at the meeting, shall record the
proceedings thereof.

    Any assistant secretaries shall have such other duties and powers as shall
be designated from time to time by the directors.

                     Section 5. RESIGNATIONS AND REMOVALS

    Any director or officer may resign at any time by delivering his
resignation in writing to the chairman of the board, if any, the president, the
treasurer or the clerk or to a meeting of the directors. Such resignation shall
be effective upon receipt unless specified to be effective at some other time. A
director (including persons elected by directors to fill vacancies in the board)
may be removed from office (a) with or without cause by the vote of the holders
of a majority of the shares issued and outstanding and entitled to vote in the
election of directors, provided that the directors of a class elected by a
particular class of stockholders may be removed only by the vote of the holders
of a majority of the shares of such class, or (b) with cause by the vote of a
majority of the directors then in office. The directors may remove any officer
elected by them with or without cause by the vote of a majority of the directors
then in office. A director or officer may be removed for cause only after
reasonable notice and opportunity to be heard before the body proposing to
remove him. No director or officer resigning, and (except where a right to
receive compensation shall be expressly provided in a duly authorized written
agreement with the corporation) no director or officer removed, shall have any
right to any compensation as such director or officer for any period following
his resignation or removal, or any right to damages on account of such removal,
whether his compensation be by the month or by the year or otherwise; unless in
the case of a resignation, the directors, or in the case of a removal, the body
acting on the removal, shall in their or its discretion provide for
compensation.

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                             Section 6. VACANCIES

    Any vacancy in the board of directors, including a vacancy resulting from
the enlargement of the board, may be filled by the stockholders or, in the
absence of stockholder action, by the directors by vote of a majority of the
directors then in office. If the office of the president or the treasurer or the
clerk becomes vacant, the directors may elect a successor. If the office of any
other officer becomes vacant, the directors may elect or appoint a successor by
vote of a majority of the directors present. Each such successor shall hold
office for the unexpired term, and in the case of the president, the treasurer
and the clerk, until his successor is chosen and qualified, or in each case
until he sooner dies, resigns, is removed or becomes disqualified. The directors
shall have and may exercise all their powers notwithstanding the existence of
one or more vacancies in their number.

                           Section 7. CAPITAL STOCK

    7.1.  Number and Par Value. The total number of shares and the par value, if
any, of each class of stock which the corporation is authorized to issue shall
be as stated in the articles of organization.

    7.2.  Fractional Shares. The corporation shall not issue fractional shares
of stock but may issue scrip in registered or bearer form which shall entitle
the holder to receive a certificate for a full share upon surrender of such
scrip aggregating a full share, the terms and conditions and manner of issue of
such scrip to be fixed by the directors.

    7.3.  Stock Certificates. Each stockholder shall be entitled to a
certificate stating the number and the class and the designation of the series,
if any, of the shares held by him, in such form as shall, in conformity to law,
be prescribed from time to time by the directors. Such certificate shall be
signed by the president or a vice president and by the treasurer or an assistant
treasurer. Such signatures may be facsimiles if the certificate is signed by a
transfer agent, or by a registrar, other than a director, officer or employee of
the corporation. In case any officer who has signed or whose facsimile signature
has been placed on such certificate shall have ceased to be such officer before
such certificate is issued, it may be issued by the corporation with the same
effect as if he were such officer at the time of its issue.

    7.4.  Loss of Certificates. In the case of the alleged loss or destruction
or the mutilation of a certificate of stock, a duplicate certificate may be
issued in place thereof, upon such conditions as the directors may prescribe.

                    Section 8. TRANSFER OF SHARES OF STOCK

    8.1.  Transfer on Books. Subject to the restrictions, if any, stated or
noted on the stock certificates, shares of stock may be transferred on the books
of the corporation by the surrender to the corporation or its transfer agent of
the certificate therefor properly endorsed or accompanied by a written
assignment and power of attorney properly executed, with necessary transfer
stamps affixed, and with such proof of the authenticity of signature as the
directors or the transfer agent of the corporation may reasonably require.
Except as may be otherwise required by law, by the articles of organization or
by these bylaws, the corporation shall be

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entitled to treat the record holder of stock as shown on its books as the owner
of such stock for all purposes, including the payment of dividends and the right
to receive notice and to vote with respect thereto, regardless of any transfer,
pledge or other disposition of such stock until the shares have been transferred
on the books of the corporation in accordance with the requirements of these
bylaws. It shall be the duty of each stockholder to notify the corporation of
his post office address.

    8.2.  Record Date and Closing Transfer Books. The directors may fix in
advance a time, which shall not be more than sixty days before the date of any
meeting of stockholders or the date for the payment of any dividend or making of
any distribution to stockholders or the last day on which the consent or dissent
of stockholders may be effectively expressed for any purpose, as the record date
for determining the stockholders having the right to notice of and to vote at
such meeting and any adjournment thereof or the right to receive such dividend
or distribution or the right to give such consent or dissent, and in such case
only stockholders of record on such record date shall have such right,
notwithstanding any transfer of stock on the books of the corporation after the
record date; or without fixing such record date the directors may for any of
such purposes close the transfer books for all or any part of such period. If no
record date is fixed and the transfer books are not closed:

         (1)  The record date for determining stockholders having the right to
notice of or to vote at a meeting of stockholders shall be at the close of
business on the date next preceding the day on which notice is given.

         (2)  The record date for determining stockholders for any other purpose
shall be at the close of business on the day on which the board of directors
acts with respect thereto.

             Section 9. INDEMNIFICATION OF DIRECTORS AND OFFICERS

    The corporation shall, to the extent legally permissible, indemnify each of
its directors and officers (including persons who serve at its request as
directors, officers or trustees of another organization in which it has any
interest, as a shareholder, creditor or otherwise) against all liabilities and-
expenses, including amounts paid in satisfaction of judgments, in compromise or
as fines and penalties, and counsel fees, reasonably incurred by him in
connection with the defense or disposition of any action, suit or other
proceeding, whether civil or criminal, in which he may be involved or with which
he may be threatened, while in office or thereafter, by reason of his being or
having been such a director, officer or trustee, except with respect to any
matter as to which he shall have been adjudicated in any proceeding not to have
acted in good faith in the reasonable belief that his action was in the best
interests of the corporation; provided, however, that as to any matter disposed
of by a compromise payment by such director or officer, pursuant to a consent
decree or otherwise, no indemnification either for said payment or for any other
expenses shall be provided unless such compromise shall be approved as in the
best interests of the corporation, after notice that it involves such
indemnification: (a) by a disinterested majority of the directors then in
office; or (b) by a majority of the disinterested directors then in office,
provided that there has been obtained an opinion in writing of independent legal
counsel to the effect that such director or officer appears to have acted in
good faith in the reasonable belief that his action was in the best interests of
the corporation; or (c) by

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the holders of a majority of the outstanding stock at the time entitled to vote-
for directors, voting as a single class, exclusive of any stock owned by any
interested director or officer. Expenses, including counsel fees, reasonably
incurred by any director or officer in connection with the defense or
disposition of any such action, suit or other proceeding may be paid from time
to time by the corporation in advance of the final disposition thereof upon
receipt of an undertaking by such director or officer to repay the amounts so
paid to the corporation if it is ultimately determined that indemnification for
such expenses is not authorized under this section. The right of indemnification
hereby provided shall not be exclusive of or affect any other rights to which
any director or officer may be entitled. As used in this section, the terms
"director" and "officer" include their respective heirs, executors and
administrators, and an "interested" director or officer is one against whom in
such capacity the proceedings in question or another proceeding on the same or
similar grounds is then pending. Nothing contained in this section shall affect
any rights to indemnification to which corporate personnel other than directors
and officers may be entitled by contract or otherwise under law.

                          Section 10. CORPORATE SEAL

    The seal of the corporation, shall, subject to alteration by the directors,
consist of a flat-faced circular die with the word "Massachusetts", together
with the name of the corporation and the year of its organization, cut or
engraved thereon.

                        Section 11. EXECUTION OF PAPERS

    Except as the directors may generally or in particular cases authorize the
execution thereof in some other manner, all deeds, leases, transfers, contracts,
bonds, notes, checks, drafts and other obligations made, accepted or endorsed by
the corporation shall be signed by the president or by one of the vice
presidents or by the treasurer.

                            Section 12. FISCAL YEAR

    The fiscal year of the corporation shall end on December 31 of each year.

                            Section 13. AMENDMENTS

    These bylaws may be altered, amended or repealed at any annual or special
meeting of the stockholders called for the purpose, of which the notice shall
specify the subject matter of the proposed alteration, amendment or repeal or
the sections to be affected thereby, by vote of the stockholders. These bylaws
may also be altered, amended or repealed by vote of a majority of the directors
then in office, except that the directors shall not take any action which
provides for indemnification of directors nor any action to amend this Section
13, and except that the directors shall not take any action unless permitted by
law.

    Any bylaw so altered, amended or repealed by the directors may be further
altered or amended or reinstated by the stockholders in the above manner.

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