[Radiosensitive Drosophila lines. III. The influencing of rad(2)201G1 mutation on the expression of damaging radiation effects in the oocytes of females].

The sensitivity of oocytes of Drosophila melanogaster to the damages induced by ionizing radiation was studied in the strain carrying rad(2)201G1 mutation and in the wild-type strain 3.4. Three days old females of these strains were treated with 1500 r of gamma-rays. Then the fertility of flies and dominant lethals in laid eggs were recorded during nine days. In addition, the number of oocytes and the frequency of their resorption in ovaries of females were counted. It has been shown that mutant females display stage-specific radiosensitivity in comparison with wild-type flies. The fertility of irradiated mutant flies has been decreased because of the delay of the development and the resorption of oocytes. Early stages of generative cells, from oogonia to oocytes-7 exhibit increased sensitivity to the resorption. Mutant egg chambers in the stages 1-7 also demonstrate a high frequency of induced dominant lethality which reaches the maximum in the oocytes 6-7. It is supposed that radiation-induced dominant lethality and resorption of immature mutant oocytes are the result of the same damages in nuclear genetical structures.