THE ACTION OF HOMOTHALLISM GENES IN SACCHAROMYCES DIPLOIDS DURING VEGETATIVE GROWTH AND THE EQUIVALENCE OF hma and HMα LOCI FUNCTIONS

[摘要] The action of homothallism genes in vegetatively growing diploid cells was examined. The results demonstrate that homothallism genes function during regular vegetative growth cycles as well as during the first few divisions after spore germination. A procedure based on ultraviolet-induced reciprocal mitotic recombination monitored by homozygosity for cryptopleurine resistance (a recessive marker closely linked to the mating-type locus) allowed us to identify and recover Saccharomyces cerevisiae colonies sectored for the mating-type locus i.e. , a / a and α/α. Homothallism genes can switch a / a or α/α vegetative diploid cells, generated from a strain with genotype a /α HO/ho HMα/HMα HM a / HM a , to a /α diploids or a / a /α/α tetraploids during a given mitotic division cycle. We found that both a / a and α/α sectors generated from a strain with genotype a /α HO/HO hmα/hmα hm a / HM a switch to a /α diploids or a / a /α/α tetraploids. This finding supports Naumov and Tolstorukov's suggestion (1973) that the hm a allele provides for the same functions as the HMα allele, namely, a switch at the mating-type locus from α to a . The HO allele is dominant to ho but hm a and HM a alleles are codominant. A loose linkage between the mating-type and the HMα loci (∼55cM), confirming Harashima, Nogi and Oshima (1974) data, was observed.

[学科分类] 医学（综合）