[The effect of the mutant genes Ta, Ra and Sd on early embryogenesis in mice]

We studied early embryonic mortality of mice from mutant stocks Tabby (Ta, X-chromosome) and RaSd (RaSd/++, chromosome 2) maintained in the heterozygous state in F1 CBA x C57B1/6 hybrid. Tabby and RaSd mice were reciprocally crossed with F1 mice and examined for the morphological status of embryos washed from the oviduct on the third day of pregnancy, when the stage of eight blastomeres is normally attained. Mortality was evaluated from the number of embryos which did not reach the expected stage by this time. The results have shown that 2-4 cell embryos, which have received gene Ta with the X-chromosome of the female parent, differed from embryos with F1 genotype at the same stage of development by their increased mortality rate, whereas among embryos obtained from RaSd, the mortality was mainly observed before cleavage. Death of embryos receiving the mutant gene from hemizygous Ta males or heterozygous RaSd/++ males was not significantly different from the mortality of embryos without these mutations.