Studies on the mutagenic action of chemical and physical agencies on yeasts. V. Effect of ultraviolet irradiation on a diploid brewery yeast

Abstract

1. Investigations in this laboratory indicated that polyploidogens are also mutagenic and that mutagens may induce polyploidy. Doubling of the chromosomes leading to viable tetraploid races is sporadic and such an induction was observed after ultra-violet irradiation. 2. Experiments were therefore carried out to confirm the suspicion that a doubling of the chromosome complement after ultra-violet irradiation may be as sporadic and unpredictable as induction of a specific gene mutation. 3. Photographs of giant colonies of the treated and the control material are presented. 4. The evidence recorded in this paper confirmed the suspicion that induction of tetraploidy being conditioned by a specific gene mutation and induced gene mutations being sporadic, treatment with ultra-violet rays does not always lead to the production of tetraploidy. 5. The existence of multiple alleles at the locus governing the nature of sculpturing of the giant colony is confirmed. 6. Ultra-violet irradiation has immediate as well as delayed effects and the nature of the mutation induced is unpredictable. 7. A theory of the mode of action of the various biologically effective physical and chemical agents on living organisms is considered.