Truncated RanGAP encoded by the Segregation Distorter locus of Drosophila

Segregation Distorter (SD) in Drosophila melanogaster is a naturally occurr ing meiotic drive system in which the SD chromosome is transmitted from SD/ SD+ males in vast: excess over its homolog owing to the induced dysfunction of SD+-bearing spermatids. The Sd Locus is the key distorting gene respons ible for this phenotype. A genomic fragment from the Sd region conferred fu ll distorting activity when introduced into the appropriate genetic backgro und by germline transformation. The only functional product encoded by this fragment is a truncated version of the RanGAP nuclear transport protein. T hese results demonstrate that this mutant RanGAP is the functional Sd produ ct.