Characterization of fractional mutations in Drosophila: differential inhibition of complete and fractional mutations by inhibitors of repair synthesis

The ‘maxy’ technique was used for scoring the frequencies of whole body and fractional mutations in the progeny of males ofDrosophila melanogasterthat had been irradiated with 2000 R, irradiation being followed or preceded by treatment with caffeine or acriflavine. Three 2-day broods were used, and males irradiated without subsidiary chemical treatment were used as controls. Both chemicals whether given as post- or pre-treatment strongly reduced the frequencies of fractional mutants in all broods. The frequency of whole-body mutants was unaffected in the first two broods and suffered a moderate reduction in the third. These results are discussed in relation to the hypothesis that repair processes regulate the development of a primary lesion into either a whole-body or a fractional mutant and that the functioning of the repair enzymes depends on the state of maturity of the male germ cell.