Abstract
Sexual orientation and courtship behavior in Drosophila are regulated by
fruitless (fru), the first gene in a branch of the sex-determination hierarchy functioning specifically in the central nervous system (CNS). The phenotypes of new
fru mutants encompass nearly all aspects of male sexual behavior. Alternative splicing of
fru transcripts produces sex-specific proteins belonging to the BTB-ZF family of transcriptional regulators. The sex-specific
fru products are produced in only about 500 of the 10
5 neurons that comprise the CNS. The properties of neurons expressing these
fru products suggest that
fru specifies the fates or activities of neurons that carry out higher order control functions to elicit and coordinate the activities comprising male courtship behavior.