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                                                                     EXHIBIT 4.2


                                  BIOTIME, INC.
                             2002 STOCK OPTION PLAN


                                    ARTICLE I
                                     GENERAL


        1.     PURPOSE

        This BioTime, Inc. Stock Option Plan (the "Plan") is intended to
increase incentive and to encourage stock ownership on the part of selected key
officers, directors, employees, consultants, professionals, and other
individuals whose efforts may aid BioTime, Inc., a California corporation (the
"Company") or any other corporations that are or which may become subsidiaries
or a parent of the Company. Except where the context obviously requires
otherwise, as used in this Plan, the term "Company" includes BioTime, Inc., a
California corporation, and any corporation that is or becomes a parent or
subsidiary, as defined in Section 425 of the Internal Revenue Code of 1986, as
amended (the "Code"), of BioTime, Inc. It is intended that certain options
granted pursuant to the Plan shall constitute incentive stock options within the
meaning of Section 422(b) of the Code and that certain other options granted
pursuant to the Plan shall not constitute incentive stock options ("nonqualified
stock options").

        2.     ADMINISTRATION

        The Plan shall be administered by the Company's Board of Directors (the
"Board") or, in the discretion of the Board, by a committee (the "Committee") of
not less than two members of the Board. The Committee's interpretation and
construction of any term or provision of the Plan or of any option granted under
the Plan shall be final, unless otherwise determined by the Board, in which
event such determination by the Board shall be final. The Committee may from
time to time adopt rules and regulations for carrying out this Plan and, subject
to the provisions of this Plan, may prescribe the form or forms of the
instruments evidencing any option granted under this Plan. No member of the
Committee shall be liable for any action or determination made in good faith
with respect to the Plan or any option granted, or with respect to any shares
sold under any restricted stock purchase agreement, under the Plan.

        Subject to the provisions of this Plan, the Board or the Committee shall
have full and final authority in its discretion to select the eligible persons
to whom options are granted or shares are sold under restricted stock purchase
agreements, to grant such options and to sell shares as provided in this Plan,
to determine the number of shares to be subject to options or sold pursuant to
restricted stock purchase agreements, to determine the exercise prices of
options or purchase prices of shares under restricted stock purchase agreements,
the terms of exercise of options, expiration dates of options, and other
pertinent terms and provisions of options and restricted stock purchase
agreements. The Board may delegate to the Committee the power to make all
determinations with respect to the Plan, or may delegate to the Committee only
certain



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aspects of Plan administration, such as selecting the eligible persons to whom
options will be granted, or decisions concerning the timing, pricing, and amount
of a grant or award of options or sale of shares under restricted stock purchase
agreements.

        3.     ELIGIBILITY

        Subject to Section 2 of this Article I, the persons who shall be
eligible to receive options or to purchase shares under restricted stock
purchase agreements under the Plan shall be such officers, employees, directors,
consultants, professionals, and independent contractors of the Company as the
Board of Directors or the Committee may select. Eligible persons who are not
also salaried employees of the Company shall be eligible to receive nonqualified
stock options (but such persons shall not be eligible to receive incentive stock
options).

        4.     SHARES OF STOCK SUBJECT TO THE PLAN

        The shares that may be issued under the Plan shall be authorized and
unissued or reacquired common shares, no par value, of the Company (the
"Shares"). The aggregate number of Shares which may be issued under the Plan
shall not exceed 1,000,000, unless an adjustment is required in accordance with
Article III.

        5.     AMENDMENT OF THE PLAN

        The Board may, insofar as permitted by law, from time to time, suspend
or discontinue the Plan or revise or amend it in any respect whatsoever, except
that no such amendment shall alter or impair or diminish any rights or
obligations under any option theretofore granted or under any restricted stock
purchase agreement executed under the Plan, without the consent of the person to
whom such option was granted or Shares were sold, except as permitted under
Section 8 of this Article I. Without further shareholder approval, no such
amendment shall increase the number of shares subject to the Plan (except as
authorized by Article III), change the designation in Section 3 of Article I of
the class of persons eligible to receive options or purchase Shares under the
Plan, extend the term during which options may be exercised, or extend the final
date upon which options under the Plan may be granted or Shares may be sold
under restricted stock purchase agreements.


        6.     APPROVAL OF SHAREHOLDERS

        All options granted under the Plan before the Plan is approved by
affirmative vote of the holders of a majority of the voting shares of the
Company present and eligible to vote at the next meeting of shareholders of the
Company, or any adjournment thereof, shall be subject to such approval. No
option granted hereunder may become exercisable unless and until such approval
is obtained.



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        7.     TERM OF PLAN

        Options may be granted and Shares may be sold under restricted stock
purchase agreements under the Plan until September 10, 2012, the date of
termination of the Plan. Notwithstanding the foregoing, each option granted
under the Plan shall remain in effect until such option has been exercised or
terminated in accordance with its terms and the terms of the Plan.

        8.     LISTING, REGISTRATION, QUALIFICATION, AND CONSENTS

        All options granted under the Plan shall be subject to the requirement
that, if at any time the Board or the Committee shall determine, in its
discretion, that the listing, registration or qualification of the shares
subject to options granted under the Plan, upon any securities exchange or under
any state or federal law, or the consent or approval of any government
regulatory body, is necessary or desirable as a condition of, or in connection
with, the granting of such option or the issuance, if any, or purchase of shares
in connection therewith, such option may not be exercised in whole or in part
unless such listing, registration, qualification, consent or approval shall have
been effected or obtained free of any conditions not acceptable to the Board or
the Committee. Furthermore, if the Board or the Committee determines that any
amendment to any option (including, but not limited to, an increase in the
exercise price) is necessary or desirable in connection with the registration or
qualification of any of its shares under any state securities or "blue sky" law,
then the Board or the Committee shall have the unilateral right to make such
changes without the consent of the optionee.

        9.     NONASSIGNABILITY

        Nonqualified options shall be transferable (i) by will, by the laws of
descent and distribution, by instrument to an inter vivos or testamentary trust
in which the nonqualified options are to be passed to beneficiaries upon the
death of the optionee or (ii) to the extent and in the manner authorized by the
Board or Committee by gift to members of the optionee's immediate family.
Immediate family means a transferee as permitted by Rule 260.140.41 of Title 10
of the California Code of Regulations which includes any child, stepchild,
grandchild, parent, stepparent, grandparent, spouse, sibling, mother-in-law,
father-in-law, son-in-law, daughter-in-law, brother-in-law, or sister-in-law and
shall also include adoptive relationships. Incentive stock options may not be
sold, pledged, assigned, hypothecated, transferred, or disposed of in any manner
other than by will or by the laws of descent or distribution and may be
exercised, during the lifetime of the optionee, only by the optionee.
Notwithstanding the preceding two sentences, in conjunction with the exercise of
an option, and for the purpose of obtaining financing for such exercise, the
option holder may arrange for a securities broker/dealer to exercise an option
on the option holder's behalf, to the extent necessary to obtain funds required
to pay the exercise price of the option.



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        10.    WITHHOLDING TAXES

        Whenever Shares are to be issued upon the exercise of any option under
the Plan or under any restricted stock purchase agreement, the Company shall
have the right to require the optionee or purchaser to remit to the Company an
amount sufficient to satisfy federal, state, and local withholding tax
requirements prior to the delivery of any certificate or certificates for such
Shares.

        11.    DEFINITION OF "FAIR MARKET VALUE"

        For the purposes of this Plan, the term "fair market value," when used
in reference to the date of grant of an option or the date of surrender of
Shares in payment for the purchase of Shares pursuant to the exercise of any
option, as the case may be, shall mean the amount determined by the Board or the
Committee as follows:

               (a) If the Shares are listed or have unlisted trading privileges
on a national securities exchange (which for the purposes of this Plan shall
also include the Nasdaq Stock Market National Market), the Shares shall be
valued at their last sale price on the principal national securities exchange
(measured by volume of transactions in such Shares) on which such securities
shall have traded, or, if available, such sales price as reported on the
composite tape, on the last trading day immediately preceding the date of grant
or surrender.

               (b) If the Shares are described in either subparagraph (a) or (b)
above but were not traded on the last trading day immediately preceding the date
of grant or surrender, or if prices of the Shares are quoted in the National
Association of Securities Dealers, Inc., Automated Quotation system (but which
not the National Market System), or if prices of the Shares are published by the
National Quotation Bureau, Inc., then the Shares shall be valued at the average
between the last bid and the last asked prices reported in the Wall Street
Journal or published by the National Quotation Bureau within the 30 days prior
to the date of grant or surrender.

               (c) If the Shares are not described in and valued under
subparagraphs (a) and (b) above, then the Shares shall be valued by the Board or
the Committee, in its sole judgement, in good faith.


                                   ARTICLE II
                                  STOCK OPTIONS

        1.     AWARD OF STOCK OPTIONS

        Awards of stock options may be made under the Plan under all the terms
and conditions contained herein. However, in the case of incentive stock
options, the aggregate fair market value (determined as of the date of grant of
the option) of the Shares with respect to which incentive stock options are
exercisable for the first time by such officer or key employee during



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any calendar year (under all incentive stock option plans of the Company) shall
not exceed $100,000. The date on which any option is granted shall be the date
of the Board's or the Committee's authorization of such grant or such later date
as may be determined by the Board or the Committee at the time such grant is
authorized.

        2.     TERM OF OPTIONS AND EFFECT OF TERMINATION

        Notwithstanding any other provision of the Plan, an option shall not be
exercisable after the expiration of ten (10) years from the date of its grant.
In addition, notwithstanding any other provision of the Plan, no incentive stock
option granted under the Plan to a person who, at the time such option is
granted, owns shares possessing more than 10% of the total combined voting power
of all classes of shares of the Company or of any parent or subsidiary
corporation, shall be exercisable after the expiration of five (5) years from
the date of its grant.

        In the event that any outstanding option under the Plan expires by
reason of lapse of time or otherwise is terminated or canceled for any reason,
then the Shares subject to any such option which have not been issued pursuant
to the exercise of the option shall again become available in the pool of Shares
for which options may be granted under the Plan.

        3.     CANCELLATION OF AND SUBSTITUTION FOR OPTIONS

        The Company shall have the right to cancel any option at any time before
it otherwise would have expired by its terms and to grant to the same optionee
in substitution therefor a new stock option stating an option price which is
lower (but not higher) than the option price stated in the canceled option. Any
such substituted option shall contain all the terms and conditions of the
canceled option provided, however, that notwithstanding Section 2 of Article II,
such substituted option shall not be exercisable after the expiration of ten
(10) years from the date of grant of the canceled option.

        4.     TERMS AND CONDITIONS OF OPTIONS

        Options granted pursuant to the Plan shall be evidenced by agreements in
such form as the Board or the Committee shall from time to time determine, which
agreements shall comply with the following terms and conditions.

               (a) Number of Shares and Type of Option

               Each option agreement shall state the number of Shares for which
the option is exercisable and whether the option is intended to be an incentive
stock option or a nonqualified stock option.



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               (b) Option Price

               Each option agreement shall state the exercise price per share or
the method by which such price shall be computed. The exercise price per share
shall be determined by the Board or the Committee at the date such option is
granted. In the case of a nonqualified option, the exercise price may be not
less than 85% of the fair market value of the Shares on the date such option is
granted. In the case of an incentive stock option, the exercise price shall be
not less than 100% of the fair market value of the Shares on the date such
option is granted. Notwithstanding the foregoing, the exercise price per share
of a option granted to a person who, on the date of such grant and in accordance
with Section 425(d) of the Code, owns shares possessing more than 10% of the
total combined voting power of all classes of shares of the Company or of any
parent or subsidiary corporation, shall be not less than 110% of the fair market
value of the Shares on the date that the option is granted.

               (c) Medium and Time of Payment

               The exercise price shall be payable upon the exercise of an
option in the lawful currency of the United States of America or, in the
discretion of the Board or the Committee, in Shares or in a combination of such
currency and such Shares. Upon receipt of payment, the Company shall deliver to
the optionee (or person entitled to exercise the option) a certificate or
certificates for the Shares purchased through such exercise.

               (d) Exercise of Options

               Options granted under the Plan shall vest, and thereby become
exercisable, at the time or times, or upon the happening of the events or
circumstances, determined by the Board or the Committee. All options granted to
employees who are not officers, directors, or consultants shall vest at a rate
not less than 20% per year over 5 years from the date of sale. Options granted
to officers, directors, and consultants may vest at any time or from time to
time upon the satisfaction of reasonable conditions to vesting determined by the
Board or Committee. Without limiting the other events and circumstances upon
which vesting may be determined, the Board or Committee may make vesting
conditioned upon continued employment by the Company. The terms under which
options shall vest shall be stated in each option agreement. The Board or the
Committee may, in its discretion, accelerate (but not delay or postpone) the
time or times at which an option vests.

               To the extent that an option has become vested (except as
provided in Article III), and subject to the foregoing restrictions, it may be
exercised in whole or in such lesser amount as may be authorized by the option
agreement. If exercised in part, the unexercised portion of an option shall
continue to be held by the optionee and may thereafter be exercised as herein
provided.



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               (e) Termination of Employment Except By Disability or Death

               In the event that an optionee who is an employee of the Company
shall cease to be employed by the Company for any reason other than his or her
death or disability, his or her option shall terminate on the date (3) months
after the date that he ceases to be an employee of the Company. The Committee or
the Board may waive the provisions of this Subsection 4(e) at the date of grant
of an option or at a later date.

               (f) Disability of Optionee

               If an optionee who is an employee of the Company shall cease to
be employed by the Company by reason of his or her becoming disabled, such
option shall terminate on the date one (1) year after cessation of employment
due to such disability. Disability means that an employee is unable to carry out
the responsibilities and functions of the position held by the employee by
reason of any medically determinable physical or mental impairment. The
Committee or the Board may waive the provisions of this Subsection 4(f) at the
time of grant of an option or at a later date if the option is not an incentive
stock option.

               (g) Death of Optionee and Transfer of Option

               If an optionee should die while in the employ of the Company, or
within the three-month period after termination of his or her employment with
the Company during which he or she is permitted to exercise an option in
accordance with Subsection 4(f) of this Article II, such option shall terminate
on the date one (1) year after the optionee's death. During such one- year
period, such option may be exercised by the executors or administrators of the
optionee's estate or by any person or persons who shall have acquired the option
directly from the optionee by his or her will or the applicable law of descent
and distribution. During such one year period, such option may be exercised with
respect to the number of Shares for which the deceased optionee would have been
entitled to exercise it at the time of his or her death. The Committee or the
Board may waive the provisions of this Subsection 4(g) at the date of grant of
an option or at a later date if the option is not an incentive stock option.

                                   ARTICLE III
                      RECAPITALIZATIONS AND REORGANIZATIONS

        The number of Shares covered by the Plan, and the number of Shares and
price per share of each outstanding option, shall be proportionately adjusted
for any increase or decrease in the number of issued and outstanding Shares
resulting from a subdivision or consolidation of Shares or the payment of a
stock dividend, or any other increase or decrease in the number of issued and
outstanding Shares effected without receipt of consideration by the Company.

        Upon the dissolution or liquidation of the Company, or upon a
reorganization, merger or consolidation of the Company as a result of which the
outstanding securities of the class then subject to options hereunder are
changed into or exchanged for cash or property or securities not of the
Company's issue, or upon a sale of substantially all the property of the Company
to, or the



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acquisition of shares representing more than eighty percent (80%) of the voting
power of the shares of the Company then outstanding by, another corporation or
person, the Plan shall terminate, and all options theretofore granted hereunder
shall terminate, unless provision can be made in writing in connection with such
transaction for the continuance of the Plan and/or for the assumption of options
theretofore granted, or the substitution for such options of options covering
the shares of a successor corporation, or a parent or a subsidiary thereof, with
appropriate adjustments as to the number and kind of shares and prices, in which
event the Plan and options theretofore granted shall continue in the manner and
under the terms so provided.

        To the extent that the foregoing adjustments relate to shares or
securities of the Company, such adjustments shall be made by the Board, whose
determination in that respect shall be final, binding and conclusive.

        The grant of an option pursuant to the Plan shall not affect in any way
the right or power of the Company to make adjustments, reclassifications,
reorganizations or changes or its capital or business structure or to merge or
to consolidate or to dissolve, liquidate or sell, or transfer all or any part of
its business or assets.

                                   ARTICLE IV
              SALE OF RESTRICTED STOCK IN LIEU OF GRANT OF OPTIONS

               (a) Number of Shares

               Each restricted stock purchase agreement shall state the number
of Shares sold under such agreement.

               (b) Purchase Price

               Each restricted stock purchase agreement shall state the purchase
price per Share or the method by which such price shall be computed. The
Purchase price per Share shall be determined by the Board or the Committee at
the date the sale of the Shares is approved (the "Approval Date"); provided that
the purchase price per Share may be not less than 85% of the fair market value
per Share on the Approval Date and that if the restricted shares are sold to an
individual who owns shares representing more than ten percent of the voting
power of all classes of shares of the Company (or any parent or subsidiary of
the Company), the purchase price per Share may not be less than 100% of the fair
market value per Share on the Approval Date.

               (c) Medium and Time of Payment

               The purchase price shall be payable at the time the restricted
stock purchase agreement is executed by the eligible person. Payment shall be
made in the lawful currency of the United States of America or, in the
discretion of the Board or the Committee, by delivery of a promissory note
payable to the Company in such lawful currency. Upon receipt of payment, the
Company shall deliver to the eligible person a certificate or certificates for
the Shares purchased.



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               (d) Repurchase Option

               Each restricted stock purchase agreement shall provide that the
Company shall have the option to repurchase the Shares sold under such agreement
in the event the purchaser ceases to be a full time employee of the Company
prior to the vesting of such Shares, or if any other condition to the vesting of
the Shares stated in the restricted stock purchase agreement is not met (the
"Repurchase Option"). The Repurchase Option may be exercised by the Company
during such period as specified in the applicable restricted stock purchase
agreement. The price at which the Company may repurchase the Shares upon the
exercise of the Repurchase Option shall be the price at which the Shares were
sold to the eligible person, or such greater price as provided in the applicable
restricted stock purchase agreement approved by the Board or the Committee. If
the purchaser of Shares under a restricted stock purchase agreement has
delivered a promissory note as payment of all or part of the purchase price of
his or her Shares, the Company may cancel or reduce the principal balance and
interest accrued on that promissory note as payment of all or part of the
repurchase price upon exercise of the Repurchase Option.

               (e) Vesting of Shares. Shares sold pursuant to a restricted stock
purchase agreement shall vest, and thereby cease to be subject to the Repurchase
Option, at the time or times, or upon the happening of the events or
circumstances, determined by the Board or the Committee. All Shares sold to
employees who are not officers, directors, or consultants shall vest at a rate
not less than 20% per year over 5 years from the date of sale. Shares sold to
officers, directors, and consultants may vest at any time or from time to time
upon the satisfaction of reasonable conditions to vesting determined by the
Board or Committee. Without limiting the other events and circumstances upon
which vesting may be determined, the Board or Committee may make vesting
conditioned upon continued employment by the Company. The terms under which
Shares shall vest shall be stated in the restricted stock purchase agreement.
The Board or the Committee may, in its discretion, accelerate (but not delay or
postpone) the time or times at which Shares vest under a restricted stock
purchase agreement.

        2. Escrow of Unvested Shares. The Company may require that all Shares
sold under a restricted stock purchase agreement be held in escrow, on terms
satisfactory to the Company, until such Shares have vested and have been paid
for in full (including the payment of any amount due on any promissory note
delivered by the purchaser and secured by such Shares).

        3. Legend on Stock Certificates. Shares issued under a restricted stock
purchase agreement shall include, in addition to any other legends as may be
required by law or by the Board or Committee, a legend to the following effect:

        THESE SHARES MAY BE TRANSFERRED ONLY IN ACCORDANCE WITH THE TERMS OF AN
        AGREEMENT BETWEEN THE COMPANY AND THE SHAREHOLDER, A COPY OF WHICH IS ON
        FILE WITH THE SECRETARY OF THE COMPANY.



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                                    ARTICLE V
                            MISCELLANEOUS PROVISIONS

        1.     RIGHTS AS A STOCKHOLDER

        An optionee or a transferee of an option shall have no rights as a
shareholder with respect to any Shares covered by an option until the date of
the receipt of payment (including any amounts required by the Company pursuant
to Section 10 of Article I) by the Company. No adjustment shall be made as to
any option for dividends (ordinary or extraordinary, whether in cash, securities
or other property) or distributions or other rights for which the record date is
prior to such date, except as provided in Article III.

        2.     MODIFICATION, EXTENSION AND RENEWAL OF OPTIONS AND RESTRICTED
               STOCK PURCHASE AGREEMENTS

        Subject to the terms and conditions and within the limitations of the
Plan, the Board or the Committee may modify, extend, renew, or cancel
outstanding options granted under the Plan and restricted stock purchase
agreements. Notwithstanding the foregoing, however, no modification of an option
or restricted stock purchase agreement shall, without the consent of the
optionee or purchaser, impair or diminish any rights or obligations under any
option theretofore granted o restricted stock purchase agreement executed under
the Plan, except as provided in Section 8 of Article I. For purposes of the
preceding sentence, the right of the Company pursuant to Section 3 of Article II
to cancel any outstanding option and to issue in place of such canceled option a
substituted option stating a lower option price shall not be construed as
impairing or diminishing an optionee's rights or obligations.

        3.     OTHER PROVISIONS

        The option agreements and restricted stock purchase agreements
authorized under the Plan shall contain such other provisions, including,
without limitation, restrictions upon the exercise of the option or purchase of
Shares, or restrictions required by any applicable securities laws, as the Board
or the Committee shall deem advisable.

        4.     APPLICATION OF FUNDS

        The proceeds received by the Company from the sale of Shares pursuant to
the exercise of options or under restricted stock purchase agreements will be
used for general corporate purposes.

        5.     NO OBLIGATION TO EXERCISE OPTION

        The granting of an option shall impose no obligation upon the optionee
or a transferee of the option to exercise such option.



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        6.     FINANCIAL ASSISTANCE

        Except as may be prohibited by law, the Company is vested with authority
under this Plan to assist any employee to whom an option is granted or to whom
Shares are sold pursuant to a restricted stock purchase agreement hereunder
(including any director or officer of the Company or any of its subsidiaries who
is also an employee) in the payment of the purchase price payable on exercise of
that option or under that restricted stock purchase agreement, by lending the
amount of such purchase price (including accepting a promissory note executed by
the employee as consideration for the sale of the Shares at the time the Shares
are issued) to such employee on such terms and at such rates of interest and
upon such security (or unsecured) as shall have been authorized by or under
authority of the Board or the Committee.

        7.     FINANCIAL REPORTS.

        The Company shall deliver to each grantee of an option a balance sheet
of the Company as at the end of its most recently completed fiscal year, and an
income statement of the Company as of the end of such fiscal year. Such
financial statements shall be delivered no less frequently than annually;
provided, that such financial statements need not be delivered to any employee
whose duties as an employee assure them access to such financial information.



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