Analysis of Y-linked temperature-sensitive mutations in Drosophila melanogaster causing male sterility or great aspirations

A number of EMS-induced heat-sensitive and cold-sensitive male sterile mutations were recovered on an XY chromosome. All mutations which recovered fertility in the presence of a free Y chromosome were classified as Y-linked. Of the Y- linked hs mutations, all were fertile with a free Y[sup L] fragment, while the cs mutations were fertile with a Y[sup S] fragment. Ten of the hs Y-linked mutations were studied in detail; eight of these were shown to be unambiguously located on Y[sup L], and had a temperature sensitive period coinciding with spermatid differentiation. Two of the hs mutant stocks were double mutations and at least one of these stocks had an X-linked mutation which interacted with the Y chromosome. This stock had a tsp which, although exerting its effect during spermio- genesis, was prior to that of the mutations located on Y[sup L]. Of the 5 cs mutations classified as Y-linked, at least three were shown to be mutations on the X chromosome which interacted with Y[sup S] The tsp's of these mutations are either pre-or early post-meiotic. Thus, no ts mutations were recovered on Y[sup S]. These results suggest that: 1) the fertility factors on Y[sup L] are present in single copies and produce products which are directly involved in spermiogenesis, 2) the genes on Y[sup S] could have a regulatory function during spermatogenesis, and either do not produce products which are thermo-labile, or are present in multiple copies, 3) there are a class of genes on the X chromosome which affect spermatogenesis through interaction with the Y chromosome. Several models were proposed to account for this X-Y chromosome interaction.Medicine, Faculty ofMedical Genetics, Department ofGraduat