Distribution of micronuclei among single cells of pre-implantation mouse embryos after X-irradiation in vitro.

The frequency of micronuclei within single cells of pre-implantation mouse embryos in vitro was determined after X-irradiation. The embryos were irradiated in the late G2 phase of the two-cell stage (32 h p.c.) with doses between 0.5 and 14 Gy. The micronuclei were counted 48 h p.c. (with most of the control embryos in the four-cell stage) and 55 h p.c. (with most of the control embryos in the eight-cell stage). The distribution of micronuclei among the single cells of the embryos does not follow a Poisson distribution, but shows a clear tendency to over-dispersion.