Sex determination in mammals

Studies on people and mice with sex chromosome abnormalities have established that the gene switching embryonic development into the male rather than the female pathway is located on the short arm of the Y chromosome in both species. How the gene exerts its effects is still a mystery. The male-specific H-Y antigen has been proposed as a possible testis inducer, but is now known to play no part in sex determination. In mice, the gene is believed to be first expressed in the Sertoli cells of the testis, in a cell-autonomous manner. A candidate gene for testis determination in man has recently been cloned, so future progress is likely to be rapid.