The Role of sry in Mammalian Sex Determination

The testis-determining gene is the Y-linked gene responsible for initiatingthe developmental pathway leading to testis formation in males. A strategy basedon determining the precise chromosomal location of this locus has been used toclone a new gene which has been called SRY in humans (Sry in mice). A varietyof studies now show that this is indeed the testis-determining gene. Sry has a spatialand temporal pattern of expression which correlates with the initiation of testisdifferentiation. The amino acid sequence encoded by the gene suggests that theprotein may function as a transcription factor, which fits well with models of sexdetermination. Some cases of XY sex reversal in humans and mouse have beenattributed to mutations in SRY/Sry, indicating that it is normally necessary fortestis determination. The finding that a genomic fragment carrying Sry can causeinale development in XX mice has proved that Sry is the only gene from the Ychromosome necessary for testis determination.