Effect of Rate of Cell Division on RNA Synthesis in Developing Frog Embryos

ENDODERM cells of developing Xenopus laevis 1 and Rana pipiens embryos 2,3 synthesize more RNA per cell, including DNA-like RNA, than do the more rapidly dividing ectoderm–mesoderm cells. Slowing the rate of cell division by culturing frog embryo explants in LiCl increases the amount of RNA synthesized per cell, including DNA-like RNA 2 , while increasing the rate of cell division by exposure to NaHCO 3 has the opposite effect 3 . These data suggest that a reduction in the rate of cell division allows higher levels of RNA (including DNA-like RNA) to be synthesized per cell.