ACTION OF HOMOTHALLISM GENES IN SACCHAROMYCES DIPLOIDS DURING VEGETATIVE GROWTH AND EQUIVALENCE OF HMA AND HM-ALPHA LOCI FUNCTIONS

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  • 1 January 1977
    • journal article
    • research article
    • Vol. 85  (3) , 407-416
Abstract
The action of homothallism genes in vegetatively growing diploid cells was examined. Homothallism genes functioned during regular vegetative growth cycles and during the 1st few divisions after spore germination. A procedure based on UV-induced reciprocal mitotic recombination monitored by homozygosity for cryptopleurine resistance (a recessive marker closely linked to the mating-type locus) identified and recovered S. cerevisiae colonies sectored for the mating-type locus i.e., a/a and .alpha./.alpha.. Homothallism genes switched a/a or .alpha./.alpha. vegetative diploid cells, generated from a strain with genotype a/.alpha. HO/ho HM.alpha./HM.alpha. HMa/HMa, to a/.alpha. diploids or a/a/.alpha./.alpha. tetraploids during a given mitotic division cycle. Both a/a and .alpha./.alpha. sectors generated from a strain with genotype a/.alpha. HO/HO hm.alpha./hm.alpha. hma/HMa switched to a/.alpha. diploids or a/a/.alpha./.alpha. tetraploids. The hma allele provided for the same function as the HM.alpha. allele, namely, a switch at the mating-type locus from .alpha. to a. The HO allele was dominant to ho but hma and HMa alleles were codominant. A loose linkage between the mating-type and the HM.alpha. loci (.apprx. 55 centi-Morgans) was observed.