[Effect of different factors on the sex ratio in laboratory mouse embryogenesis]

Influence of two factors on distribution of embryos according to the sex is considered: genetic peculiarities of inbred mice and hybrid mice, as well as spontaneous embryonal death of the embryos of different sex. The work has been performed on C3H, CBA, C57BL strains of mice and on hybrid mice of CBA/C57BL and ICR/In(X)1H strains. The sex ratio in the mice studied is balanced. In the CBA/C57BL hybrid mice a certain shift in the sex ratio is noted towards female embryos. In the offspring of the ICR/In(X)1H hybrid mice the sex distribution of the embryos does not differ from the ratio 1:1. The results of the investigation confirm the opinion of the literature that genetic peculiarities of the inbred mice do not essentially influence the sex ratio in their offspring, while fluctuation in the sex ratio in the hybrid mice are evidently connected, in a greater degree, with their genetic peculiarities. As demonstrates the analysis of the sex relation and the embryonal death, there is no selective death in the embryos of any sex during embryogenesis in the mice investigated.