Y sex-determining region: A region on the Y chromosome that determines the sex of the individual. This region goes by the symbol SRY (sex region Y). SRY is necessary and sufficient for male sex determination. It is the testis-determining factor.
Mutations in SRY give rise to XY females with gonadal dysgenesis who appear to be normal females at birth, but at puberty do not develop secondary sexual characteristics (breasts, etc.), do not menstruate, and have streak (fibrous) gonads without eggs. There is a high incidence of neoplasia (gonadoblastoma and germinoma) in the streak gonads.