<PAGE>

                MORGAN STANLEY DEAN WITTER SELECT EQUITY TRUST
           THE COMPETITIVE EDGE BEST IDEAS PORTFOLIO SERIES 2001-1
                          REFERENCE TRUST AGREEMENT

          This Reference Trust Agreement dated January 30, 2001 between DEAN
WITTER REYNOLDS INC., as Depositor, and The Bank of New York, as Trustee,
sets forth certain provisions in full and incorporates other provisions by
reference to the document entitled "Dean Witter Select Equity Trust, Trust
Indenture and Agreement" (the "Basic Agreement") dated September 30, 1993, as
amended. Such provisions as are incorporated by reference constitute a single
instrument (the "Indenture").

                               WITNESSETH THAT:
                               ---------------

          In consideration of the premises and of the mutual agreements
herein contained, the Depositor and the Trustee agree as follows:

                                      I.

                    STANDARD TERMS AND CONDITIONS OF TRUST

          Subject to the provisions of Part II hereof, all the provisions
contained in the Basic Agreement are herein incorporated by reference in
their entirety and shall be deemed to be a part of this instrument as fully
and to the same extent as though said provisions had been set forth in full
in this instrument except that the Basic Agreement is hereby amended as
follows:

          A.   The first sentence of Section 2.01 is amended to add the
     following language at the end of such sentence: "and/or cash (or a
     letter of credit in lieu of cash) with instructions to the Trustee to
     purchase one or more of such Securities which cash (or cash in an amount
     equal to the face amount of the letter of credit), to the extent not
     used by the Trustee to purchase such Securities within the 90-day period
     following the first deposit of Securities in the Trust, shall be
     distributed to Unit Holders on the Distribution Date next following such
     90-day period or such earlier date as the Depositor and the Trustee
     determine".

<PAGE>

                                     -2-

          B.   Section 2.03 is amended to add the following to the end of the
     first paragraph thereof. The number of Units may be increased through a
     split of the Units or decreased through a reverse split thereof, as
     directed by the Depositor, which revised number of Units shall be
     recorded by Trustee on its books.

          C.   The first sentence of Section 2.06 is amended to add the
     following language after "Securities"))": "and/or cash (or a letter of
     credit in lieu of cash) with instructions to the Trustee to purchase one
     or more Additional Securities which cash (or cash in an amount equal to
     the face amount of the letter of credit), to the extent not used by the
     Trustee to purchase such Additional Securities within the 90-day period
     following the first deposit of Securities in the Trust, shall be
     distributed to Unit Holders on the Distribution Date next following such
     90-day period or such earlier date as the Depositor and the Trustee
     determine".

          D.   Article III, entitled "Administration of Trust", Section 3.01
     Initial Cost shall be amended as follows:

          Section 3.01 Initial Cost shall be amended to substitute the
following language:

          SECTION 3.01. INITIAL COST The costs of organizing the Trust and
     sale of the Trust Units shall, to the extent of the expenses
     reimbursable to the Depositor provided below, be borne by the Unit
     Holders, PROVIDED, HOWEVER, that, to the extent all of such costs are
     not borne by Unit Holders, the amount of such costs not borne by Unit
     Holders shall be borne by the Depositor and, PROVIDED FURTHER, HOWEVER,
     that the liability on the part of the Depositor under this section shall
     not include any fees or other expenses incurred in connection with the
     administration of the Trust subsequent to the deposit referred to in
     Section 2.01. Upon notification from the Depositor that the primary
     offering period is concluded, the Trustee shall withdraw from the
     Account or Accounts specified in the Prospectus or, if no Account is
     therein specified, from the Principal Account, and pay to the Depositor
     the Depositor's reimbursable expenses of organizing the Trust and sale
     of the Trust Units in an amount certified to the Trustee by the
     Depositor. If the balance of the Principal Account is insufficient to
     make such withdrawal, the Trustee shall, as di-

<PAGE>

                                     -3-

     rected by the Depositor, sell Securities identified by the Depositor, or
     distribute to the Depositor Securities having a value, as determined
     under Section 4.01 as of the date of distribution, sufficient for such
     reimbursement. The reimbursement provided for in this section shall be
     for the account of the Unitholders of record at the conclusion of the
     primary offering period and shall not be reflected in the computation of
     the Unit Value prior thereto. As used herein, the Depositor's
     reimbursable expenses of organizing the Trust and sale of the Trust
     Units shall include the cost of the initial preparation and typesetting
     of the registration statement, prospectuses (including preliminary
     prospectuses), the indenture, and other documents relating to the Trust,
     SEC and state blue sky registration fees, the cost of the initial
     valuation of the portfolio and audit of the Trust, the initial fees and
     expenses of the Trustee, and legal and other out-of-pocket expenses
     related thereto, but not including the expenses incurred in the printing
     of preliminary prospectuses and prospectuses, expenses incurred in the
     preparation and printing of brochures and other advertising materials
     and any other selling expenses. Any cash which the Depositor has
     identified as to be used for reimbursement of expenses pursuant to this
     Section shall be reserved by the Trustee for such purpose and shall not
     be subject to distribution or, unless the Depositor otherwise directs,
     used for payment of redemptions in excess of the per-Unit amount
     allocable to Units tendered for redemption.

          E.   The third paragraph of Section 3.05 is hereby amended to add
     the following sentence after the first sentence thereof:  "Depositor may
     direct the Trustee to invest the proceeds of any sale of Securities not
     required for the redemption of Units in eligible money market
     instruments selected by the Depositor which will include only negotiable
     certificates of deposit or time deposits of domestic banks which are
     members of the Federal Deposit Insurance Corporation and which have,
     together with their branches or subsidiaries, more than $2 billion in
     total assets, except that certificates of deposit or time deposits of
     smaller domestic banks may be held provided the deposit does not exceed
     the insurance coverage on the instrument (which currently is $100,000),
     and provided further that the Trust's aggregate holding of certificates
     of deposit or time deposits issued by the Trustee may not ex-

<PAGE>

                                     -4-

     ceed the insurance coverage of such obligations and U.S. Treasury notes
     or bills (which shall be held until the maturity thereof) each of which
     matures prior to the  earlier of the next following Distribution Date or
     90 days after receipt, the principal thereof and interest thereon (to
     the extent such interest is not used to pay Trust expenses) to be
     distributed on the earlier of the 90th day after receipt or the next
     following Distribution Date."

          F.   The first sentence of each of Sections 3.10, 3.11 and 3.12 is
     amended to insert the following language at the beginning of such
     sentence, "Except as otherwise provided in Section 3.13,".

          G.   The following new Section 3.13 is added

          Section 3.13. EXTRAORDINARY EVENT-SECURITY RETENTION AND VOTING. In
     the event the Trustee is notified of any action to be taken or proposed
     to be taken by holders of the securities held by the Trust in connection
     with any proposed merger, reorganization, spin-off, split-off or
     split-up by the issuer of stock or securities held in the Trust, the
     Trustee shall take such action or refrain from taking any action, as
     appropriate, so as to insure that the securities are voted as closely as
     possible in the same manner and in the same general proportion as are
     the securities held by owners other than the Trust. If stock or
     securities are received by the Trustee, with or without cash, as a
     result of any merger, reorganization, spin-off, split-off or split-up by
     the issuer of stock or securities held in the Trust, the Trustee at the
     direction of the Depositor may retain such stock or securities in the
     Trust. Neither the Depositor nor the Trustee shall be liable to any
     person for any action or failure to take action with respect to this
     section.

          H.   Section 1.01 is amended to add the following definition:  (9)
     "Deferred Sales Charge" shall mean any deferred sales charge payable in
     accordance with the provisions of Section 3.14 hereof, as set forth in
     the prospectus for a Trust.  Definitions following this definition (9)
     shall be renumbered.

          I.   Section 3.05 is hereby amended to add the following paragraph
     after the end thereof: On each Deferred Sales Charge payment date set
     forth in the prospectus for

<PAGE>

                                     -5-

     a Trust, the Trustee shall pay the account created pursuant to Section
     3.14 the amount of the Deferred Sales Charge payable on each such date
     as stated in the prospectus for a Trust. Such amount shall be withdrawn
     from the Principal Account from the amounts therein designated for such
     purpose.

          J.   Section 3.06B(3) shall be amended by adding the following:
     "and any Deferred Sales Charge paid".

          K.   Section 3.08 shall be amended by adding the following at the
     end thereof: "In order to pay the Deferred Sales Charge, the Trustee
     shall sell or liquidate an amount of Securities at such time and from
     time to time and in such manner as the Depositor shall direct such that
     the proceeds of such sale or liquidation shall equal the amount required
     to be paid to the Depositor pursuant to the Deferred Sales Charge
     program as set forth in the prospectus for a Trust.

          L.   Section 3.14 shall be added as follows:

          Section 3.14. Deferred Sales Charge. If the prospectus for a Trust
     specifies a Deferred Sales Charge, the Trustee shall, on the dates
     specified in and as permitted by the prospectus, withdraw from the
     Income Account if such account is designated in the prospectus as the
     source of the payments of the Deferred Sales Charge, or to the extent
     funds are not available in that account or if such account is not so
     designated, from the Principal Account, an amount per Unit specified in
     the prospectus and credit such amount to a special, non-Trust account
     maintained at the Trustee out of which the Deferred Sales Charge will be
     distributed to the Depositor. If the Income Account is not designated as
     the source of the Deferred Sales Charge payment or if the balances in
     the Income and Principal Accounts are insufficient to make any such
     withdrawal, the Trustee shall, as directed by the Depositor, either
     advance funds, if so agreed to by the Trustee, in an amount equal to the
     proposed withdrawal and be entitled to reimbursement of such advance
     upon the deposit of additional monies in the Income Account or the
     Principal Account, sell Securities and credit the proceeds thereof to
     such special Depositor's account or credit Securities in kind to such
     special Depositor's Account. Such directions shall identify the
     Securities, if any, to be

<PAGE>

                                     -6-

     sold or distributed in kind and shall contain, if the Trustee is
     directed by the Depositor to sell a Security, instructions as to
     execution of such sales. If a Unit Holder redeems Units prior to full
     payment of the Deferred Sales Charge, the Trustee shall, if so provided
     in the prospectus, on the Redemption Date, withhold from the Redemption
     Price payment to such Unit Holder an amount equal to the unpaid portion
     of the Deferred Sales Charge and distribute such amount to such special
     Depositor's account or, if the Depositor shall purchase such Unit
     pursuant to the terms of Section 5.02 hereof, the Depositor shall pay
     the Redemption Price for such Unit less the unpaid portion of the
     Deferred Sales Charge. The Depositor may at any time instruct the
     Trustee to distribute to the Depositor cash or Securities previously
     credited to the special Depositor's account.

          M.   The Distribution Agency Agreement is amended to be applicable
     to the Morgan Stanley Dean Witter Select Equity Trust, The Competitive
     Edge Best Ideas Portfolio series.

          N.   Reference to "Dean Witter Select Equity Trust" is replaced by
     "Morgan Stanley Dean Witter Select Equity Trust".

                                     II.

                     SPECIAL TERMS AND CONDITIONS OF TRUST

          The following special terms and conditions are hereby agreed to:

          A.   The Trust is denominated Morgan Stanley Dean Witter Select
Equity Trust The Competitive Edge Best Ideas Portfolio Series 2001-1 (the
"Best Ideas Trust").

          B.   The publicly traded stocks listed in Schedule A hereto are
those which, subject to the terms of this Indenture, have been or are to be
deposited in trust under this Indenture.

          C.   The term, "Depositor" shall mean Dean Witter Reynolds Inc.

<PAGE>

                                     -7-

          D.   The aggregate number of Units referred to in Sections 2.03 and
9.01 of the Basic Agreement is 25,066 for the Best Ideas Trust.

          E.   A Unit is hereby declared initially equal to 1/25,066th for
the Best Ideas Trust.

          F.   The term "In-Kind Distribution Date" shall mean April 11, 2002.

          G.   The term "Record Dates" shall mean October 1, 2001, and May 1,
2002 and such other date as the Depositor may direct. (Such dates are set forth
for the purposes of distribution to Unit Holders. Trust expenses shall be paid
quarterly.)

          H.   The term "Distribution Dates shall mean October 15, 2001 and on
or about May 8, 2002 and such other date as the Depositor may direct. (Such
dates are set forth for the purposes of distribution to Unit Holders. Trust
expenses shall be paid quarterly.)

          I.   The term "Termination Date" shall mean May 1, 2002.

          J.   The Depositor's Annual Portfolio Supervision Fee shall be a
maximum of $0.25 per 100 Units.

          K.   The Trustee's Annual Fee as defined in Section 6.04 of the
Indenture shall be $0.80 per 100 Units.

          L.   For a Unit Holder to receive an "in-kind" distribution during
the life of the Trust, such Unit Holder must tender at least 25,000 Units for
redemption. There is no minimum amount of Units that a Unit Holder must
tender in order to receive an "in-kind" distribution on the In-Kind Date or
in connection with a rollover.

          M.   The Indenture is amended to provide that the period during
which the Trustee shall liquidate the Trust Securities shall not exceed 14
business days commencing on the first business day following the In-Kind Date.

              (Signatures and acknowledgments on separate pages)

<PAGE>

                                     -8-

          The Schedule of Portfolio Securities in the prospectus included in
this Registration Statement is hereby incorporated by reference herein as
Schedule A hereto.