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 rel evant factor through the analysis of Y-autosome translocations using f luorescence 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 DN A sequences from Drosophila hydei. Clone pY114 labeled most of the lon g arm and pDh2-H8 hybridizes to the short arm and the centromeric regi on 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 wit h the length of the Y fragment still present in these aberrant individ uals and allowed us to map the male-determining factor to a region of the long arm representing similar to 15% of the entire Y chromosome. N o additional factors, affecting for example fertility, were detected o utside the male-determining region.