A SHIFT OF SEX-RATIO IN THE PROGENY FROM IRRADIATED MALES IN <i>DROSOPHILA MELANOGASTER</i>

Abstract

On the basis of the hypothesis that sex-ratio is mainly altered by radiation-induced lethals on either paternal or maternal sex-chromosomes, it has, in general, been thought that the hereditary effects of radiation on man may be assessed by investigating a shift of sex-ratio in the progeny from irradiated parents.In man, Kaplan (1957), Turpin et al. (1956), Schull and Neel (1958) and Tanaka and Okura (1958) reported that when fathers were irradiated the sex-ratio (sons/sons+ daughters) in their children increased, while it decreased if mothers were irradiated, as expected from the hypothesis mentioned above. However, Macht and Lawrence (1955) and Neel and Schull (1956) found no significant difference between the sex-ratios of children from irradiated parents and those from non-irradiated ones. Furthermore, the remarkable fact became clear that abnormal sexuality can be caused by exceptional behavior of sex-chromosomes in parental meiosis (Ford et al. 1959;Jacobs and Strong 1959). The experiment of Russell et al. (1958Russell et al. ( , 1960) with mice showed a quite different result from the expectation based on the mutation hypothesis.On the other hand, Lindsley et al. (1958) and Herskovitz and Baumiller (1959) reported that in Drosophila irradiation with high doses failed to induce any shift in the sex-ratio of the progeny, contrary to the early results obtained by others (Hanson 1928;Muller 1928;Gowen and Gay 1933;Bauer 1939;Demerec and Fano 1944;Catchside and Lea 1945).The facts indicated above suggest that the sex-ratio is affected not only by induced sex-linked lethals, but also by some other factors such as abnormal behavior of sexchromosomes due to radiation ; i. e., radiation-induced non-disjunction or elimination of the sex-chromosomes. In fact, Savhagen (1961a, b) revealed that a considerable amount of non-disjunction or elimination of sex-chromosomes could be induced by X-rays in Drosophila melanogaster, the amount depending on the stage in which the germ cells were irradiated. Thus, the assessment of hereditary effects of radiation on man based on a sex-ratio shift in the progeny from irradiated parents seems to have encountered some new difficulties, among which, first of all, must be included the effect of irradiation of different germ cell stages on the mutation rates. In addition to the idea that dominant