|                                            | 1.     |                                            | I have      reviewed this quarterly report on Form 10-Q of Geron Corporation;                                                                                                                                                                                                                                                                                          |
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|                                            | 2.     |                                            | Based      on my knowledge, this report does not contain any untrue statement of a      material fact or omit to state a material fact necessary to make the      statements made, in light of the circumstances under which such statements      were made, not misleading with respect to the period covered by this      report;                                    |
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|                                            | 3.     |                                            | Based      on my knowledge, the financial statements, and other financial information      included in this report, fairly present in all material respects the      financial condition, results of operations and cash flows of the      registrant as of, and for, the periods presented in this report;                                                            |
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|                                            | 4.     |                                            | The      registrant’s other certifying officer(s) and I are responsible for      establishing and maintaining disclosure controls and procedures (as      defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal      control over financial reporting (as defined in Exchange Act Rules      13a-15(f) and 15d-15(f)) for the registrant and have: |
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|                                            |   |                                            | (a)                                                                                                                                                                                                                                                                                                                                                                    |  | Designed such      disclosure controls and procedures, or caused such disclosure controls and      procedures to be designed under our supervision, to ensure that material      information relating to the registrant, including its consolidated      subsidiaries, is made known to us by others within those entities,      particularly during the period in which this report is being      prepared; |
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|                                            |   |                                            | (b)                                                                                                                                                                                                                                                                                                                                                                    |  | Designed such      internal control over financial reporting, or caused such internal control      over financial reporting to be designed under our supervision, to provide      reasonable assurance regarding the reliability of financial reporting and      the preparation of financial statements for external purposes in      accordance with generally accepted accounting principles; |
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|                                            |   |                                            | (c)                                                                                                                                                                                                                                                                                                                                                                    |  | Evaluated the      effectiveness of the registrant’s disclosure controls and procedures and      presented in this report our conclusions about the effectiveness of the      disclosure controls and procedures, as of the end of the period covered by      this report based on such evaluation; and |
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|                                            |   |                                            | (d)                                                                                                                                                                                                                                                                                                                                                                    |  | Disclosed in this      report any change in the registrant’s internal control over financial      reporting that occurred during the registrant’s most recent fiscal quarter      (the registrant’s fourth fiscal quarter in the case of an annual report)      that has materially affected, or is reasonably likely to materially      affect, the registrant’s internal control over financial reporting;      and |
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|                                            | 5.     |                                            | The      registrant’s other certifying officer(s) and I have disclosed, based on      our most recent evaluation of internal control over financial reporting,      to the registrant’s auditors and the audit committee of the registrant’s      board of directors (or persons performing the equivalent      functions):                          |
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|                                            |   |                                            | (a)                                                                                                                                                                                                                                                                                                                                                                    |  | All significant      deficiencies and material weaknesses in the design or operation of      internal control over financial reporting which are reasonably likely to      adversely affect the registrant’s ability to record, process, summarize      and report financial information; and |
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|                                            |   |                                            | (b)                                                                                                                                                                                                                                                                                                                                                                    |  | Any fraud,      whether or not material, that involves management or other employees who      have a significant role in the registrant’s internal control over      financial reporting. |

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