[Hybridization of cells of the same mating type in Saccharomyces yeasts].

The problem of mating-type switches in heterothallic yeast cells was investigated. 93% of non-mating hybrids were obtained in a X a crosses. The hybrids obtained in alpha X alpha crosses expressed alpha-mating type predominantly. Hybrids with no major rearrangements or loss of chromosome III were detected among these hybrids. In the selective system for cytoduction in a X a crosses the significant part of all cytoductants were alpha-maters, i.e. those originated through a----alpha switches. In alpha X alpha crosses alpha cytoductants were predominantly obtained either spontaneously or after UV-irradiation, though the frequency of cytoductants after UV-irradiation exceeded the control value several times. So, we developed the method for selection of mating-type "switchers" (a in equilibrium alpha), avoiding the diploid stage, and demonstrated the possibility of hybridization among the alpha-cells without hereditary changes at the MAT locus.