A technique to establish systems of haploid to polyploid Saccharomyces strains which are most identical with respect to their chromosome sets and most homozygous

Abstract It is necessary to have series of most homozygous strains with identical chromosome sets to study, i.e. radiation effects or gene dosis relationships in Saccharomyces strains of different ploidy, because it could be shown that changes in the genetic background within a serie influence the effect under study (Laskowski 1962, Haefner 1964, 1965a). With all techniques used up to now it is not possible to avoid either some necessary heterozygousities, or a high amount of divisions, which automatically introduce spontaneous mutations and therefore deviations from the identity of the chromosome sets in different strains. Laskowski (1962), using a technique of Mortimer (1958), was able to establish a system of Saccharomyces strains of the ploidy p = 1 to 6, but with the disadvantage that strains with p > 2 were heterozygous for the mating type locus and strains with p > 4 were additional heterozygous for two necessary marker genes. Emeis (1963) established series of polyploid strains with‐even p‐values by selecting cells, which derived from endomitotic divisions.