Abstract
For the interpretation of radiation induced inactivations of microorganisms a multi-target model (a) is frequently used which assumes at least implicitly that only recessive lethal mutations are responsible for the effect. This model is criticized once because it disregards certainly existent dominant lethal mutations as well as cytoplasmic effects and secondly because it employes a highly specialized formula. Proposals are made for the use of a more complete and less specialized formula. The observed crossing of dose-effect-curves of haploid and diploid yeast strains can be explained by this mathematical theory. The importance of the use of endomitotically originated strains of different ploidy and complete homozygous constitution is emphasized. Such strains are available in Saccharomyces.