Notwithstanding their biological importance, Y chromosomes remain poorly known in most species. I am studying the origin and evolution of these chromosomes, particularly in the Drosophila genus. A major obstacle to the study of Y-chromosomes is the identification of their sequences: due to its high content of repetitive sequences, in most genome projects the Y is fragmented into a large number of small, unmapped contains. I am developing computational and experimental methods to accomplish this, that has lead to the identification of nearly all known Drosophila Y-linked genes. Identification of Drosophila Y-chromosome genes yielded important insights on its origin and evolution.