<prompt> What function do vitamin B12 and folic acid perform that is critical to hematopoiesis?Suppo porphyrin productionServe as cofactors for iron uptakeSuppo terminal differentiation of erythroid and myeloid cellsSuppo production of thymidine triphosphate  <response>: Cell proliferation requires DNA replication, which requires an adequate supply of thymidine triphosphate. Both vitamin B12 and folate are needed to make thymidine triphosphate. 