Information from specific-locus mutants on the nature of induced and spontaneous mutations in the mouse.

Genetic and molecular analyses of mutations are increasing the qualitative capabilities of the specific-locus test (SLT). Some mutations are found to be deletions of large numbers of genes, including some that control survival at various developmental stages, neurological functions, enzyme syntheses, etc. Smaller (including possibly single-gene) deletions are also detected. A third group of SLT mutations represents intragenic lesions. -- For at least three of the loci, mutations may now be qualitatively grouped on the basis of simple phenotypic findings. Type of mutagen and germ-cell stage exposed strongly influence the nature of the lesions. The qualitative information from SLT results makes possible conclusions about relative potential harmfulness of different types of exposures that may yield equal mutation rates, about differences between induced and spontaneous mutations, etc. It also identifies genetic material suitable for basic studies.