Phenotypic expression of primary lesions of genetic material in Saccharomyces yeasts.
"Illegitimate" mating of yeasts (alpha x alpha), either spontaneous or induced by uv light or ethyl methanesulfanate, in a selective system for "cytoduction" revealed that about 95% of cytoductants expressed their original (alpha) mating type. Inducing the mating by treating the recipient of cytoplasm with uv light reached two orders of magnitude. An additional copy of MAT alpha in the alpha recipient almost completely eliminated the effect, which means that nonheritable mating type changes observed are formally recessive and are localized within MAT alpha complex. About 1% of cytoductants obtained were nonmating types and some of them were identified as mat alpha l mutants. Radl8 mutant as a recipient showed a considerably elevated spontaneous frequency of illegitimate hybridization and cytoduction. The cytoductants also preserved the original mating type. These facts suggest that nonheritable changes of mating type are due to repairable primary (premutational) lesions in MAT alpha genetic material. The significance of these results for understanding the mechanism of nonheritable variability is discussed.
Inge-Vechtomov
S G
SG
Department of Genetics and Breeding, Leningrad State University, U.S.S.R.
Repnevskaya
M V
MV
D004249:DNA Damage; D004260:DNA Repair; D004271:DNA, Fungal / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D005020:Ethyl Methanesulfonate / Q000494:pharmacology; D005800:Genes, Fungal / Q000187:drug effects / Q000528:radiation effects; D000072235:Mating Factor; D009152:Mutagenicity Tests; D010455:Peptides / Q000235:genetics; D010641:Phenotype; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D014466:Ultraviolet Rays
D004271:DNA, Fungal; D010455:Peptides; D000072235:Mating Factor; D005020:Ethyl Methanesulfonate