[Demonstration of dominant lethal mutations in early mouse embryogenesis]

Male mice of C57Bl/6Y strain were injected intraperitoneally with 2.5 and 5 mg/kg doses of thioTEPA. Males were mated to tetrahybrid CBWA females during the second week after the treatment. Embryonic mortality was studied by two methods: by standard dominant lethal method on the 15-17th day of pregnancy and cytologically on the 4th day. The rate of fertilization was not affected by thioTEPA. After treatment with 2.5 mg/kg of thioTEPA the frequency of induced dominant lethals was 89.8%; preimplantation losses were 78,5% in treated and 13,8% in control group. The cytological analysis revealed that preimplantation embryonic death is equal to 63,9%. The death of embryos before implantation occurred at 2-20 blastomere stages. After treatment with 5 mg/kg of thioTEPA all embryos died before implantation at 2-16 blastomere stages. It was demonstrated that dominant lethal method gave more complete estimation of dominant lethal frequency, and that cytological analysis is the correct estimation of preimplantation death. Thus the methods used supplement each other.