DISCRIMINATION OF RELATED TRANSCRIBED AND NONTRANSCRIBED REPETITIVE DNA-SEQUENCES FROM THE Y-CHROMOSOMES OF DROSOPHILA-HYDEI AND DROSOPHILA-EOHYDEI

The short arm of the Y chromosome of Drosophila hydei carries a single male fertility gene, gene e, which forms the lampbrush loop pair Noos es. Conflicting observations have been reported concerning the identit y of the repetitive DNA sequences that are transcribed in this loop pa ir. It has been claimed by other investigators that the loop transcrip ts contain repeats of two distinct, but related families of Y-specific repetitive DNA sequences, ay1 and YsI. We reinvestigated this issue, using as probes single ay1 and YsI repeats which, under stringent cond itions, hybridize only to members of their own family. Under non-strin gent conditions, both repeats hybridize in situ to Nooses transcripts. However, if hybridization conditions are stringent, only the ay1 prob e hybridizes to loop transcripts. Hybridizations to Northern blots of testis RNA confirm these results. Further, YsI repeats are not found t he closely related species D. eohydei. We conclude that the YsI repeat s are not relevant for the function of fertility gene Q.