Genetic Fine Structure of the Y Chromosome of Drosophila Hydei

A genetic map of the Y chromosome of Drosophila hydei has been constructed from deletion/complementation experiments, with the aid of male sterile mutants of the Y chromosome. A central conclusion of our experiments is that not more than a single complementation group can be detected in each of the lampbrush loop forming sites. Additional complementation groups, functionally independent of lampbrush loops, reside between these loci. Six complementation groups have been defined by several methods of mapping. An additional ten complementation groups are indicated, but their exact definition requires further investigation. The "synthetic sterility" of mutations in these ten loci contributes to the difficulty in unequivocally establishing their individual boundaries. Mapping problems also arise from the instability of certain mutants.