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  <xsd:element id="lyel_SuccessLiabilitiesMember" name="SuccessLiabilitiesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="lyel_TenTimesMember" name="TenTimesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="lyel_ThirtyTimesMember" name="ThirtyTimesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="lyel_TwentyTimesMember" name="TwentyTimesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="lyel_TwoThousandEighteenEquityIncentivePlanMember" name="TwoThousandEighteenEquityIncentivePlanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="lyel_TwoThousandTwentyOneEmployeeStockPurchasePlanMember" name="TwoThousandTwentyOneEmployeeStockPurchasePlanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="lyel_TwoThousandTwentyOneEquityIncentivePlanMember" name="TwoThousandTwentyOneEquityIncentivePlanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="lyel_UnauditedCondensedConsolidatedFinancialStatementsPolicyTextBlock" name="UnauditedCondensedConsolidatedFinancialStatementsPolicyTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="lyel_DescriptionOfOrganizationTable" name="DescriptionOfOrganizationTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="lyel_ScheduleOfAggregatePotentialSuccessPaymentsTableTextBlock" name="ScheduleOfAggregatePotentialSuccessPaymentsTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="lyel_CollaborationLicenseAndSuccessPaymentAgreementsTextBlock" name="CollaborationLicenseAndSuccessPaymentAgreementsTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="lyel_OtherInvestmentsTextblock" name="OtherInvestmentsTextblock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
</xsd:schema>
