LIMITED POWER OF ATTORNEY FOR
                        SECTION 16 REPORTING OBLIGATIONS

     Know all by these presents, that the undersigned hereby makes, constitutes
and appoints each of James Weissman, Douglas W. Pagan and Tim Bernstein, or
either of them acting individually, and with full power of substitution, the
undersigned's true and lawful attorney-in-fact to:

     (1)   prepare, execute in the undersigned's name and on the undersigned's
           behalf, and submit to the U.S. Securities and Exchange Commission
           (the "SEC") a Form ID, including amendments thereto, and any other
           documents necessary or appropriate to obtain codes and passwords
           enabling the undersigned to make electronic filings with the SEC of
           reports required by Section 16(a) of the Securities Exchange Act of
           1934 (the "Exchange Act") or any rule or regulation of the SEC;

     (2)   execute for and on behalf of the undersigned, in the undersigned's
           capacity as an officer and/or director of Dicerna Pharmaceuticals,
           Inc., a Delaware corporation (the "Company"), Forms 3, 4, and 5,
           including amendments thereto, in accordance with Section 16(a) of the
           Exchange Act and the rules and regulations thereunder;

     (3)   seek or obtain, as the undersigned's representative and on the
           undersigned's behalf, information on transactions in the Company's
           securities from any third party, including brokers, employee benefit
           plan administrators and trustees, and the undersigned hereby
           authorizes any such person to release any such information to such
           attorney-in-fact and approves and ratifies any such release of
           information;

     (4)   do and perform any and all acts for and on behalf of the undersigned
           which may be necessary or desirable to complete and execute any such
           Form 3, 4, or 5, complete and execute any amendment or amendments
           thereto, and timely file such form with the SEC and any stock
           exchange or similar authority; and

     (5)   take any other action of any type whatsoever in connection with the
           foregoing which, in the opinion of such attorney-in-fact, may be of
           benefit to, in the best interest of, or legally required by, the
           undersigned, it being understood that the documents executed by such
           attorney-in-fact on behalf of the undersigned pursuant to this Power
           of Attorney shall be in such form and shall contain such terms and
           conditions as such attorney-in-fact may approve in such attorney-in-
           fact's discretion.

     The undersigned hereby grants to each such attorney-in-fact full power and
authority to do and perform any and every act and thing whatsoever requisite,
necessary, or proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all that such attorney-in-fact, or such
attorney-in-fact's substitute or substitutes, shall lawfully do or cause to be
done by virtue of this power of attorney and the rights and powers herein
granted. The undersigned acknowledges that the foregoing attorneys-in-fact, in
serving in such capacity at the request of the undersigned, are not assuming nor
relieving, nor is the Company assuming nor relieving, any of the undersigned's
responsibilities to comply with Section 16 of the Exchange Act.  The undersigned
acknowledges that neither the Company nor the foregoing attorneys-in-fact assume
(i) any liability for the undersigned's responsibility to comply with the
requirement of the Exchange Act, (ii) any liability of the undersigned for any
failure to comply with such requirements, or (iii) any obligation or liability
of the undersigned for profit disgorgement under Section 16(b) of the Exchange
Act.

     This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file such forms with respect to the
undersigned's holdings of and transactions in securities issued by the Company,
unless earlier revoked by the undersigned in a signed writing delivered to the
foregoing attorneys-in-fact. This Power of Attorney supersedes any prior power
of attorney in connection with the undersigned's capacity as an officer and/or
director of the Company. This Power of Attorney shall expire as to any
individual attorney-in-fact if such attorney-in-fact ceases to be an employee of
the Company.

     IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of this July 5, 2020.

                                        /s/ Douglas Fambrough
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                                        Signature

                                        Douglas Fambrough
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