<PAGE>

                                                                   Exhibit 10.26

                             EMPLOYMENT AGREEMENT

     This Employment Agreement (the "Agreement") is made as of March 15, 2000,
by and between Genomica Corporation, with principal offices at 4001 Discovery
Drive, Suite 130, Boulder, Colorado 80303 (the "Company"), and Thomas G. Marr
("Executive").

     Whereas, Executive is currently employed by the Company as its President,
Chief Scientist and a Director; and

     Whereas, the Company desires to employ the Executive in the capacity and
under the terms and conditions hereinafter set forth, and Executive is willing
to be so employed by the Company;

     Now, Therefore, in consideration of the promises and the mutual agreements
herein set forth, the parties hereto agree to the following terms and conditions
of the Executive's employment:

     1.  Employment.  The Company hereby continues to employ Executive and
Executive hereby accepts such continued employment upon the terms and conditions
set forth herein and agrees to perform such duties as are commensurate with his
office as prescribed by the Board of Directors of the Company, effective March
15, 2000 ("Effective Date"). The Executive's employment, as provided herein,
shall commence on the Effective Date of this Agreement and shall continue until
terminated pursuant to the provisions of paragraph 11 hereof.

     It is understood and agreed by the Company and Executive that this
     Agreement does not contain any promise or representation concerning the
     duration of Executive's employment with the Company.  Executive
     specifically acknowledges that his employment with the Company is at-will
     and may be altered or terminated by either Executive or the Company at any
     time, with or without cause and/or with or without notice.  In addition,
     that the rate of salary, other compensation, or stock option vesting
     schedules are stated in units of years or months does not alter the at-will
     nature of the employment, and does not mean and should not be interpreted
     to mean that Executive is guaranteed employment to the end of any period of
     time or for any period of time.  Any oral representation, custom, habit or
     practice, or any other writing cannot change the nature, terms or
     conditions of Executive's employment with the Company.  In the event of
     conflict between this disclaimer and any other statement, oral or written,
     present or future, concerning terms and conditions of employment, the at-
     will relationship confirmed by this disclaimer shall control.  This at-will
     status cannot be altered except in writing signed by Executive and the
     Chairman of the Board of Directors.

     2.  Duties.  Executive shall render exclusive, full-time services to the
Company as its President, Chief Scientist and a Director. Executive's
responsibilities, title, working conditions, duties and/or any other aspect of
Executive's employment may be changed, added to or eliminated during his
employment at the sole discretion of the Company. During the term of his


<PAGE>

employment hereunder, the Executive shall devote his best efforts and his full
business time, skill and attention to the performance of his duties on behalf of
the Company.

     3.  Policies and Procedures.  Executive agrees that he is subject to and
will comply with the policies and procedures of the Company, as such policies
and procedures may be modified, added to or eliminated from time to time at the
sole discretion of the Company, except to the extent any such policy or
procedure specifically conflicts with the express terms of this Agreement.
Executive further agrees and acknowledges that any written or oral policies and
procedures of the Company do not constitute contracts between the Company and
Executive.

     4.  Compensation.  For all services rendered and to be rendered hereunder,
and for the other agreements by the Executive contained herein, the Company
agrees to pay to the Executive, and the Executive agrees to accept a salary of
$225,000 per annum. Such salary will be reviewed no less frequently than
annually, and may be increased (but not decreased, unless as set forth herein)
at the discretion of the Company's Board of Directors or Compensation Committee.
Any such salary shall be payable pursuant to the Company's payroll procedures
which may be changed by the Company from time to time and shall be subject to
such deductions or withholdings as the Company is required to make pursuant to
law, or by further agreement with the Executive.

     5.  Stock.  Executive, pursuant to the terms and conditions set forth in
the Common Stock Acquisition Agreement and the Founders Purchase Agreement
(collectively referred to herein as the "Founders Agreement") purchased
1,080,000 shares of the Company's stock for the price of $1,080.00. The terms
and conditions of Founders Agreement shall remain in full force and effect and
are not modified by anything contained herein. The Common Stock Acquisition
Agreement and the Founders Purchase Agreement are attached hereto as Exhibit A.

     6.  Stock Options.  The Company, pursuant to its Amended and Restated 1996
Stock Option Plan (the "Plan"), the Stock Option Agreement dated April 10, 1997
(the "1997 Option Agreement") and the Notice of Grant of Stock Options and
Option Agreement dated April 10, 1997 (the "Grant Notice"), granted Executive an
option to purchase 250,000 shares of the Company Common Stock at an exercise
price of $.06 per share. The terms and conditions of the Plan, the 1997 Option
Agreement and the Grant Notice shall remain in full force and effect and are not
modified by anything contained herein. The Plan, the 1997 Option Agreement and
the Grant Notice are attached hereto as Exhibits B, C & D respectively. In
addition, the Company, pursuant to the Plan, the Stock Option Agreement (the
"Option Agreement"), and the Stock Option Grant Notices, including Attachments
I, II, and III thereto, dated May 27, 1999, November 30, 1999 and January 27,
2000 ("Second Grant Notices"), granted Executive an option, to purchase 200,000
shares of the Company Common Stock at an exercise price of $.06 per share, to
purchase 100 shares of the Company Common Stock at an exercise price of $.06 per
share and to purchase 1,000,000 shares of the Company Common Stock at an
exercise price of $.25 per share respectively. The terms and conditions of the
Plan, the Option Agreement and the Second Grant Notices shall remain in full
force and effect and are not modified by anything contained herein. The Plan,
the Option Agreement and the Second Grant Notices are attached hereto as
Exhibits B, E, F, G & H respectively. In addition, Executive is a Named
Executive pursuant to the Plan.



                                      8.
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     7.   Other Benefits.  While employed by the Company as provided herein:

          (a)  The Executive shall be entitled to all benefits to which other
executive officers of the Company are entitled, on terms comparable thereto,
including, without limitation, participation in any and all pension and profit
sharing plans, group insurance policies and plans, medical, health, and
disability insurance policies and plans, and the like, which may be maintained
by the Company for the benefit of its executives. The Company reserves the right
to from time to time alter and amend the benefits received by Executive, at the
Company's sole discretion.

          (b)  The Executive shall receive, against presentation of proper
vouchers, reimbursement for direct and reasonable out-of-pocket expenses
incurred by him in connection with the performance of his duties hereunder,
according to the policies of the Company.

          (c)  The Executive shall be entitled to personal time off, sick time
off, holidays and other paid absences in accordance with Company policies in
effect from time to time.

     8.   Proprietary and Other Obligations.  Executive agrees to continue to
be bound by the terms and conditions contained in Executive's Employee
Proprietary Information and Inventions Agreement dated December 15, 1999
("Confidentiality Agreement") attached as Exhibit I and acknowledges that the
Confidentiality Agreement remains in full force and effect.

     9.   Non-competition and Non-solicitation.  Executive acknowledges that he
will be a member of executive and management personnel at the Company. Executive
further acknowledges that during his employment at the Company, he will be privy
to extremely sensitive, confidential and valuable commercial information, which
constitutes trade secrets belonging to the Company, the disclosure of which
information and secrets would greatly harm the Company.

          (a)  Definitions.

               (i)  Conflicting Product or Service.  As used in this Agreement,
a "Conflicting Product or Service" means any computer program, product, process,
system, development tool, application, or service of any person or organization
other than the Company, in existence or under development, which competes with a
computer program, product, process, system, development tool, application, or
service of the Company, that is being or has been marketed, under development,
or part of the Company's business development plans at such time as the
Executive terminates employment with the Company.

               (ii) Conflicting Organization.  As used in this Agreement, a
"Conflicting Organization" means any person or organization other than the
Company that is engaged in or is about to become engaged in the design,
research, development, production, marketing, distribution, leasing, licensing,
selling, or servicing of a Conflicting Product or Service.

          (b)  Covenant Not to Compete.  As a reasonable measure to protect the
Company from the harm of such disclosure and use of its information and trade
secrets against it,



                                      3.
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Executive agrees to the following as part of this Agreement: Executive agrees
that he shall not, individually or together with others, directly or indirectly,
during his employment with the Company and for a period of one year following
the separation of Executive's employment with the Company, for any reason,
whether as an owner, consultant, partner, joint venturer, stockholder, broker,
agent, financial agent, principal, trustee, licensor or in any other capacity
whatsoever (a) own, manage, operate, join, control, finance or participate in
the ownership, management, operation, control or financing of, or be connected
as an officer, director, executive, partner, principal, agent, representative,
consultant, licensor, licensee or otherwise with, any business or enterprise
which is a Conflicting Organization, and (b) sell or assist in the design,
development, manufacture, licensing, sale, marketing or support of any
Conflicting Product or Service, or engage in any other manner, in any
Conflicting Organization. The parties agree that no more than 1% of the
outstanding voting stock of a publicly traded company or any stock currently
owned by Executive shall not constitute a violation of this paragraph. Executive
further agrees and acknowledges that because of the nature and type of business
that the Company engages in, the geographic scope of the covenant not to compete
shall include all counties, cities, and states of the United States and any
other country, territory or region in which the Company conducts business and
that such a geographic scope is reasonable. Nothing in this paragraph should be
construed to narrow the obligations of Executive imposed by any other provision
herein, any other agreement, law or other source.

          (c)  Non-solicitation Covenant.  As a reasonable measure to protect
the Company from the harm of such disclosure and use of its information and
trade secrets against it, the parties agree to the following as part of this
Agreement: Executive acknowledges and agrees that information regarding
employees of the Company is Confidential Information, including without
limitation, the names of the Company employees; information regarding the skills
and knowledge of employees of the Company; information regarding any past,
present, or intended compensation, benefits, policies and incentives for
employees of the Company; and information regarding the management and reporting
structure of the Company. Executive agrees that he will not, individually or
with others, directly or indirectly (including without limitation, individually
or through any business, venture, proprietorship, partnership, or corporation in
which they control or own more than a five (5) percent interest, through any
agents, through any contractors, through recruiters, by their successors, by
their employees, or by their assigns) solicit, or induce any employee of the
Company to leave the Company during the period he is employed by the Company and
for a period of one year following the separation, resignation, or termination
of Executive's employment with the Company. Executive further agrees that during
the period he is employed by the Company and for one year thereafter, he will
not, either directly or indirectly, solicit or attempt to solicit any customer,
client, supplier, investor, vendor, consultant or independent contractor of the
Company to terminate, reduce or negatively alter his, her or its relationship
with the Company. The geographic scope of the covenants in this paragraph 9(c)
shall include any city, county, or state of the United States and any such other
city, territory, country, or jurisdiction in which the Company does business.
Nothing in this paragraph should be construed to narrow the obligations of
Executive imposed by any other provision herein, any other agreement, law or
other source.

          (d)  Reasonable.  Executive agrees and acknowledges that the time
limitation and the geographic scope on the restrictions in this paragraph 9 and
its subparts are reasonable.


                                      4.
<PAGE>

Executive also acknowledges and agrees that the limitation in this paragraph 9
and its subparts is reasonably necessary for the protection of the Company, that
through this Agreement he shall receive adequate consideration for any loss of
opportunity associated with the provisions herein, and that these provisions
provide a reasonable way of protecting the Company's business value which was
imparted to him. In the event that any term, word, clause, phrase, provision,
restriction, or section of this paragraph 9 of this Agreement is more
restrictive than permitted by the law of the jurisdiction in which the Company
seeks enforcement thereof, the provisions of this Agreement shall be limited
only to that extent that a judicial determination finds the same to be
unreasonable or otherwise unenforceable. Moreover, notwithstanding any judicial
determination that any term, word, clause, phrase, provision, restriction, or
section of this Agreement is not specifically enforceable, the parties intend
that the Company shall nonetheless be entitled to recover monetary damages as a
result of any breach hereof.

          (e)  Legal and Equitable Remedies.  In view of the nature of the
rights in goodwill, employee relations, trade secrets, and business reputation
and prospects of the Company to be protected under this paragraph 9 of this
Agreement, Executive understands and agrees that the Company could not be
reasonably or adequately compensated in damages in an action at law for
Executive's breach of their obligations (whether individually or together)
hereunder. Accordingly, Executive specifically agrees that the Company shall be
entitled to temporary and permanent injunctive relief, specific performance, and
other equitable relief to enforce the provisions of this paragraph 9 of this
Agreement and that such relief may be granted without the necessity of proving
actual damages, and without bond. Executive acknowledges and agrees that the
provisions in this paragraph 9 and its subparts are essential and material to
this Agreement, and that upon breach of this paragraph 9 by him, the Company is
entitled to withhold providing payments or consideration, to equitable relief to
prevent continued breach, to recover damages and to seek any other remedies
available to the Company. This provision with respect to injunctive relief shall
not, however, diminish the right of the Company to claim and recover damages or
other remedies in addition to equitable relief.

          (f)  Extension of Time.  In the event that Executive breaches any
covenant, obligation or duty in this paragraph 9 or its subparts, any such duty,
obligation, or covenants to which the parties agreed by this paragraph 9 and its
subparts shall automatically toll from the date of the first breach, and all
subsequent breaches, until the resolution of the breach through private
settlement, judicial or other action, including all appeals. The duration and
length of Executive's duties and obligations as agreed by this paragraph 9 and
its subparts shall continue upon the effective date of any such settlement, or
judicial or other resolution.

     10.  Consulting Arrangement.  Upon termination of Executive's employment
by the Company for any reason and at the Company's sole discretion, Executive
agrees to enter into a consulting arrangement the terms and conditions of which
shall be mutually agreed to by the Company and Executive. Unless otherwise
agreed to, the duration of the consulting arrangement shall be no longer than
one year from such date of termination or resignation.

     11.  Termination.  Executive and the Company each acknowledge that either
party has the right to terminate Executive's employment with the Company at any
time for any reason whatsoever, with or without cause or advance notice pursuant
to the following:

                                       5.
<PAGE>

          (a)  Termination by Death or Disability.  In the event Executive
shall die during the period of his employment hereunder or become permanently
disabled, as evidenced by Executive's inability to carry out his job
responsibilities for a continuous period of six months, Executive's employment
and the Company's obligation to make payments hereunder shall terminate on the
date of his death, or the date upon which, in the sole reasonable determination
of the Board of Directors, Executive has failed to carry out his job
responsibilities for six months. The Company's ability to terminate Executive as
a result of any disability shall be to the extent permitted by state and/or
federal law.

          (b)  Voluntary Resignation by Executive.  In the event Executive
voluntarily resigns from his employment with the Company (other than for Good
Reason as defined below), the Company's obligation to make payments hereunder
shall cease upon such resignation, except the Company shall pay Executive (a)
any salary earned but unpaid prior to the resignation and all accrued but unused
vacation, and (b) any business expenses referred to in paragraph 7(b) that were
incurred but not reimbursed as of the date of resignation. Vesting of any shares
pursuant to the Plan, the Option Agreement, the First Grant Notice and the
Second Grant Notices or any other unvested shares shall cease on the date of
resignation. Should Executive voluntarily resign from his employment with the
Company, Executive agrees to be bound by the provisions of paragraph 9 (Non-
competition/Non-solicitation) for a period of one year from the date of such
resignation.

          (c)  Termination for Just Cause.  In the event Executive is
terminated by the Company for Just Cause (as defined below), the Company's
obligation to make payments hereunder shall cease upon the date of receipt by
Executive of written notice and explanation of such termination (the "date of
termination" for purposes of this paragraph 11(c)), except the Company shall:
pay Executive any salary earned but unpaid prior to termination, all accrued but
unused vacation and any business expenses referred to in paragraph 7(b) that
were incurred but not reimbursed as of the date of termination. Vesting of any
shares pursuant to the Plan, the Option Agreement, the First Grant Notice and
the Second Grant Notices or any other unvested shares shall cease on the date of
termination. In the event the Company terminates Executive for Just Cause,
Executive agrees to be bound by the provisions of paragraph 9 (Non-
competition/Non-solicitation) for a period of one year from the date of
termination.

          (d)  Termination by the Company without Just Cause or Resignation
for Good Reason. In the event that Executive is terminated by the Company for
any reason other than Just Cause (as defined below), or if the Executive shall
resign his employment for Good Reason (as defined below), the following shall
occur provided Executive signs a full general release, releasing all claims,
known or unknown that Executive may have against the Company related to
Executive's employment with the Company or the termination of said employment as
documented by the Company as of the date Executive signs such release, and upon
the written acknowledgment of his continuing obligations under the
Confidentiality Agreement, attached as Exhibit F, Executive shall receive the
following severance benefits: a) if the termination without Just Cause or the
resignation for Good Reason occurs within the first 12 months of Employment with
the Company (for purposes of this paragraph 11(d) the 12 month period shall be
measured from the Effective Date), Executive shall receive 12 months of his then
currently salary, payable monthly and less all applicable deductions and
withholdings; b) if the termination without Just

                                       6.
<PAGE>

Cause or the resignation for Good Reason occurs within the second 12 months of
employment with the Company, Executive shall receive 6 months of his then
currently salary, payable monthly and less all applicable deductions and
withholdings; and (c) if the termination without Just Cause or the resignation
for Good Reason occurs after 24 months of employment with the Company, Executive
shall receive 3 months of his then currently salary, payable monthly and less
all applicable deductions and withholdings ("Severance Payments"). The payments
shall be calculated based on his then current salary as of the termination date
and shall be paid in the normal course of the Company's payroll cycle, less all
applicable deductions and withholdings. Vesting of any shares pursuant to the
Plan, the Option Agreement, the First Grant Notice and the Second Grant Notices
or any other unvested shares shall cease on the date of termination. In the
event the Company terminates Executive for without Just Cause or Executive
resigns for Good Reason, Executive agrees to be bound by the provisions of
paragraph 9 (Non-competition/Non-solicitation) for a period of one year from the
date of termination.

               (i)  "Just Cause" for termination shall mean:  That the Company,
acting in good faith based upon the information then known to the Company,
determines that Executive has committed or engaged in: willful misconduct, gross
negligence, charges of theft, fraud, or other illegal or dishonest conduct which
are considered to be harmful to the Company by the majority vote of its Board of
Directors; refusal or unwillingness to perform material job duties, failure to
adequately perform job duties, habitual absenteeism, substantial dependence on
alcohol or any controlled substance, sexual or other forms of illegal
harassment, conduct that reflects adversely upon, or making any remarks
disparaging of the Company, its Board, Officers, Directors, advisors,
executives, affiliates or subsidiaries; insubordination; any willful act that is
likely to and which does, in fact, have the effect of materially injuring the
reputation, business, or business relationship of the Company, violation of
fiduciary duty, violation of any duty of loyalty, material breach of any
material term of this Agreement, including the Confidentiality Agreement,
Exhibit I, and matters of similar gravity to any of the above enumerated
grounds. Termination with Just Cause must be made with written notice to
Executive. In the event Executive is terminated for Just Cause he will not be
entitled to any Severance Payments, pay in lieu of notice, vesting of any shares
under any option, vesting of any unrestricted shares, or any other such
compensation set forth herein, but he will be entitled to all compensation,
benefits and unreimbursed expenses accrued through the date of termination. The
parties acknowledge that this definition of "Just Cause" in not intended and
does not apply to any aspect of the relationship between the Company and any of
its employees, including Executive, beyond determining Executive's eligibility
for the Severance Payments.

               (ii) "Good Reason" shall mean (i) relocation of your place of
work greater than fifty miles from your current work location; (ii) a decrease
in compensation; (iii) a material change in the business direction of the
Company, or (iv) the Company unilaterally makes significant detrimental changes
to the Executive's job responsibilities, which action is not remedied after
twenty (20) days written notice, and Executive notifies the Company at
termination that he is terminating for Good Reason; provided, however, that upon
the occurrence of one of the preceding events, the Executive shall be deemed to
have waived any rights to receive Severance Payments if he does not notify the
company of his intention to resign within 90 days after such event.

                                       7.
<PAGE>

     12.  Miscellaneous.

          (a)  Executive agrees to be responsible for the payment of any taxes
due on any and all compensation provided by the Company pursuant to this
Agreement. Executive agrees to indemnify the Company and hold the Company
harmless from any and all claims or penalties asserted against the Company for
any failure to pay taxes due on any compensation provided by the Company
pursuant to this Agreement. Executive expressly acknowledges that the Company
has not made, nor herein makes, any representation about the tax consequences of
any consideration provided by the Company to Executive pursuant to this
Agreement.

          (b)  This Agreement may not be amended, modified, superseded,
canceled, renewed or expanded, or any terms or covenants hereof waived, except
by a writing executed by each of the parties hereto or, in the case of a waiver,
by the party waiving compliance. Failure of any party at any time or times to
require performance of any provision hereof shall in no manner affect his or its
right at a later time to enforce the same. No waiver by a party of a breach of
any term or covenant contained in this Agreement, whether by conduct or
otherwise, in any one or more instances shall be deemed to be or construed as a
further or continuing waiver of agreement contained in the Agreement.

          (c)  This Agreement shall be binding upon and shall inure to the
benefit of any successor or assignee of the business of the Company. This
Agreement shall not be assignable by the Executive.

          (d)  All notices given hereunder shall be given by certified mail,
addressed, or delivered by hand, to the other party at his or its address as set
forth herein, or at any other address hereafter furnished by notice given in
like manner. Each notice shall be dated the date of its mailing or delivery and
shall be deemed given, delivered or completed on such date.

          (e)  This Agreement shall be governed in all respects by the laws of
the State of Colorado as such laws are applied to agreements between Colorado
residents entered into and performed entirely in Colorado, including conflict of
laws provisions of the State of Colorado.

          (f)  This Agreement together with the Exhibits attached hereto sets
forth the entire agreement and understanding of the parties hereto with regard
to the employment of the Executive by the Company and supersede all prior
agreements, arrangements and understandings, written or oral, pertaining to the
subject matter hereof. No representation, promise or inducement relating to the
subject matter hereof has been made to a party that is not embodied in these
Agreements, and no party shall be bound by or liable for any alleged
representation, promise or inducement not so set forth.

          (g)  The Executive and the Company represent and warrant to each
other that neither has incurred any liability for any employment agency or
finders fees or commissions, or the like, in connection with the employment
contemplated herein. The Executive and the Company hereby agree to indemnify and
hold each other harmless from and against and in respect of any claim for
employment agency or finders fees or commissions or the like relating to the
employment contemplated by this Agreement.

                                       8.
<PAGE>

          (h)  The following exhibits to this Agreement are attached hereto and
constitute a part of this Agreement:

               Exhibit A  --    the Common Stock Acquisition Agreement and the
                                Founders Agreement
               Exhibit B  --    the Amended and Restated 1996 Stock Option Plant
               Exhibit C  -     the Stock Option Agreement dated April 10, 1997
               Exhibit D  --    the Notice of Grant of Stock Options and Option
                                Agreement dated April 10, 1997
               Exhibit E  --    The Stock Option Agreement
               Exhibit F  --    the Stock Option Grant Notice, including
                                Attachments I, II, an III thereto, dated May 27,
                                1999
               Exhibit G  --    the Stock Option Grant Notice, including
                                Attachments I, II, an III thereto, dated
                                November 30, 1999
               Exhibit H  --    the Stock Option Grant Notice, including
                                Attachments I, II, an III thereto, dated January
                                27, 2000
               Exhibit I  --    Employee Proprietary Information and Inventions
                                Agreement dated December 15, 1999

     In Witness Whereof, the parties have each duly executed this Restated
Employment Agreement as of the day and year first above written.

                                    Genomica Corporation

                                    By: /s/ Teresa W. Ayers
                                       --------------------------------------
                                    Title: Chief Executive Officer
                                          -----------------------------------


                                    Executive:

                                    /s/ Thomas G. Marr
                                    -----------------------------------------
                                    Thomas G. Marr


                                       9.