The regulation of DNA synthesis and mitosis in multinucleate frog eggs.

The timing of DNA synthesis and mitosis in normal eggs, in activated eggs, and in eggs containing several accessory nuclei has been studied in Xenopus. DNA synthesis was followed by injecting PHjthymidine into the egg and detecting its subsequent incorporation into DNA by autoradiography. It was found that the accessory nuclei which were introduced into the egg during different phases of the cell cycle incorporated label and entered mitosis in synchrony with the resident egg and sperm nuclei if the introduced nuclei were released from the intact sperm. In eggs activated by pricking, the egg nucleus had synthesized DNA at a time when it would have done so during normal fertilization.