DNA Repair Does Not Trigger Genetic Instability of Yeast Cells

Abstract

The dependence of the delayed formation of colonies on the dose of ionizing radiation (gamma rays of 60Co, dose rate 10 Gy/min) was obtained for six strains of wild-type haploid and diploid yeast, capable of recovering from radiation damage and characterized by sigmoidal survival curves as well as for six haploid and diploid radiosensitive mutants defective in reparation and characterized by exponential survival curves. The delay in the formation of colonies by survival cells after irradiation is considered as a genetic instability display. It was shown that for all diploid strains, genetic instability reached 100% with an increase in the dose of ionizing radiation, regardless of the shape of survival curves and the cell ability to recover from radiation damage. Conversely, for all haploid strains, genetic instability was only close to 20%. In contrast to traditional concepts, these data indicate that the late formation of colonies by surviving yeast cells after irradiation is determined mainly by cell ploidy and does not depend on the shape of the dose-response curves and cell radiosensitivity. This means that DNA repair does not trigger genetic instability in yeast cells.