Detection of X-ray induced dominant lethal mutations in mice: an in vitro approach.

The expression of dominant lethal mutations induced by 450 rad of X-radiation in the germ cells of male mice was detected by an in vitro analysis. Embryos sired by irradiated males had a higher incidence of developmental failures in early cleavage, at the late morula stage, and at the late blastocyst stage due to dominant lethal mutations than did control embryos. Dominant lethal mutations were induced most frequently in germ cells exposed as early spermatids and spermatocytes and next most frequently in germ cells exposed as sperm. A decrease in fertilizations, presumably reflecting cell killing, was found in irradiated spermatocytes. These observations indicate that in vitro analysis permits a more detailed description of mutations that are expressed as preimplantation failures than does in vivo analysis.