Identification of the sex-determining region of the Ceratitis capitata Y chromosome by deletion mapping.

In the medfly Ceratitis capitata, the Y chromosome is responsible for determining the male sex. We have mapped the region containing the relevant factor through the analysis of Y-autosome translocations using fluorescence in situ hybridization with two different probes. One probe, the clone pY114, contains repetitive, Y-specific DNA sequences from C. capitata, while the second clone, pDh2-H8, consists of ribosomal DNA sequences from Drosophila hydei. Clone pY114 labeled most of the long arm and pDh2-H8 hybridizes to the short arm and the centromeric region of the long arm. In 12 of the analyzed 19 Y-autosome translocation strains, adjacent-1 segregation products survive to the late pupal or even adult stage and can, therefore, be sexed. This was correlated with the length of the Y fragment still present in these aberrant individuals and allowed us to map the male-determining factor to a region of the long arm representing approximately 15% of the entire Y chromosome. No additional factors, affecting for example fertility, were detected outside the male-determining region.