RBE of α-Particles for Delayed Production of Colonies by Irradiated Yeast Cells.

The effect of delayed colony appearance by irradiated cells exemplifying genetic instability is confirmed to be more expressed for diploid wild-type yeast cells characterized by a sigmoidal shape of the survival curve and capable of recovery from radiation damage in contrast to isogenic haploid strain incapable of diploid-specific recovery and characterized by the exponential form of the survival curve. The dependence of the delayed appearance of colonies by diploid yeast cells on the dose of ionizing radiation shows more pronounced manifestation after the action of α-particles (RBE = 4.2 ± 0.3) than after irradiation with y-rays. This effect may be associated with the greater efficiency of densely ionizing radiation to produce lethal radiation damage and accompanying sublesions responsible for the delay in the formation of colonies by the cells surviving after irradiation. It is shown that the dependence of the delayed colony appearance by diploid yeast cells on their survival was substantially the same after exposure to sparsely and densely ionizing radiation. Since exposure to ionizing radiation of different quality induced equally effective number of lethal damage and the same survival rates, these data indicate that the identical number of the accompanying sublesions responsible for the delayed colony appearance are produced by irradiated cells.