Dominant lethal mutations in male mice.

Dominant lethal mutations are due to chromosome aberrations as demonstrated by analysis of first cleavage. With a sample size of 40-45 mice per dose the induction of dominant lethal mutations by 10 mg/kg of methyl methanesulfonat (MMS) can be detected in spermatids in the mating interval 9-12 days posttreatment (6-11%). In the same mating interval a dose of 150 mg/kg of MMS induces 100% dominant lethal mutations. MMS and other chemical mutagens can be characterized by their different spermatogenic response. The germ cell stage specific induction of dominant lethal mutations by chemical agents is very likely due to their different pathways and therefore, to different effects on the structural and macromolecular changes during spermatogenesis. The feasibility of standardizing test protocol for the dominant lethal assay in mice, based on collaborative studies, is discussed. The reproducibility of results and the sensitivity of the induction of dominant lethal mutations in the collaborative studies demonstrate the usefullness of the method for mutagenicity screening.