A cytogenetic analysis of X- ray induced male steriles on the Y chromosome of Drosophila melanogaster

A total of 1020 B ^s Yy ⁺chromosomes was screened for the induction of male sterile mutations by X irradiation. The 29 recovered mutations were analyzed by genetic complementation and the metaphase chromosomes stained with Hoechst 33258 and observed with fluorescence microscopy. The cytological and genetic maps derived from this analysis were compared to similar maps of the Y chromosome mutations isolated in an earlier study (Brosseau, 1960). Unlike the previous work we have identified only 6 male fertility loci (2 on the short arm, 4 on the long arm) on the Y chromosome. These loci are distributed along the length of the long arm and are likely to reside at two separate sites on the short arm. There is no apparent clustering of these fertility factors in this heterochromatic chromosome. The deletions obtained in this study were observed to be unstable and the nature of this instability was investigated. The original Y chromosome was marked at both telomeres with normally X-linked genes. The loss of one or the other of these markers was accompanied in many cases by the concomitant loss of large segments of Y chromosome material. The possible mechanism of this loss is discussed.Author to whom correspondence should be sent