Effects of X-rays on Female Germ-cells ofDrosophila Melanogaster

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Abstract
The sensitivity in terms of dominant-lethal induction (strictly speaking : reduced hatchability) has been measured for successive eggs laid by Drosophila melanogaster after irradiation of the female with 1000, 4000 and 6000 rad. Hypersensitivity is found in eggs laid by females aged seven days, during the first 12 hours after irradiation. This is attributed to irradiation of Metaphase I. A lower level of sensitivity is found in eggs laid over the next six days. This is attributed to the irradiation of oocytes in all stages prior to Metaphase I. Finally, a residual incidence of dominant lethals is observed in eggs laid more than six days after irradiation, which are presumed to have been irradiated as oogonia. Oviposition (i.e. rate of maturation of eggs) shows an entirely different radiation response. 4000 rad produces a slight depression of egg-laying during the period of low dominant-lethal production, a more marked depression coinciding with the main production of dominant lethals, and a particularly severe depression on day 3 after irradiation. The pattern of sensitivity after 6000 rad is the same but more marked. The egg-laying rate more than six days after irradiation is slightly depressed by 4000 rad, and more so with increasing doses until 10000 rad, when complete sterility is produced. After such a dose the ovarioles are atrophied, without oocytes or oogonia.