Changes in Survival after X-Irradiation of Xenopus Embryos at Different Phases of the Cell Cycle

Xenopus embryos were exposed to 956 rads of x-rays at different times after fertilization. Cell divisions are synchronous at least in the first three cycles studied. The percentage of embryos surviving for 3 days was the criterion of sensitivity. It was found that, during the first three cleavage cycles, greatest sensitivity to x-rays was at telophase/early interphase, and least sensitivity was at late interphase. Sensitivity increases from prophase through metaphase, anaphase to telophase, and decreases throughout S. Changes in survival after x-rays approximately correspond to changes in nuclear DNA content.