GENETIC EFFECTS AFTER HEAVY ION IRRADIATION OF HAPLOID AND DIPLOID YEAST CELLS

. We have investigated the biological effects induced by different accelerated ions ( 4 He, 11 B, 12 C, 15 N, and 20 Ne) with different energies and linear energy transfers (LETs) and determined their relative biological effectiveness (RBE) for lethal damage and gene mutations. In particular, base pair substitution induction by ionizing radiation in haploid and diploid yeast Saccharomyces cerevisiae has been studied. We have detected the GC-AT transition in the haploid strain and the AT-TA transversion in the diploid strain. The RBE dependence on LET for lethal mutations is described by a curve with a local maximum at LET of about 100 keV/μm. It is shown that the mutation frequency increases with increasing the dose up to 1000 Gy for diploid cells irradiated by different ions. A decrease in RBE with increasing LET has been observed for diploid cells. However, for haploid cells irradiated at doses of up to 100 Gy, the curves seem to have a plateau. The RBE dependence on LET for haploid cells is different and also has a plateau. But for substitution induction in haploid cells, an ion beam with a high LET (177 keV/μm) is less mutagenic than the one with a low LET (44–127 keV/μm). Therefore, we have obtained different biological effects of accelerated ions for haploid and diploid cells.