Inaktivierungsversuche mit homozygoten Hefestämmen verschiedenen Ploidiegrades

Abstract

A series of homozygous Saccharomyces-strains of different ploidy (haploid to tetraploid) has been bred. Except for the mating type alleles in the tri- and tetraploid strain the genomes of these strains are completely identical. The inactivation of these strains by UV, organic peroxides, X-rays (50 kV), ²¹⁰Po-α-rays, accelerated He-, C- and O-nuclei was studied by avaluation of the ability to form macroscopic colonies. These different kinds of ionizing radiations cover a wide range of ionization density (LET). The triploid strain proved to be the most resistent one for each kind of radiation inactivation. A comparison of the RBE-values of the ionizing radiations showed a maximum at the LET-value of 1360 MeV cm² g^-1 (²¹⁰Po-a-rays). It could be shown for diploid strains that a heterozygous condition in only the mating type alleles produces a remarkable resistance for X- and ²¹⁰Po-α-rays. This effect, however, is absent in UV-inactivation.