Sex-determining region Y (SRY) or testis-determining factor (TDF) is a DNA-binding protein that generally activates the expression of male-specific genes stimulating testis differentiation.
Mutations in this gene and lack of SRY protein lead to the formation of XY females with gonadal dysgenesis. These individuals do not develop secondary sexual characteristics. Due to the lack of SRY gene, testes are not formed, whereas functional female gonads are also absent. Therefore, impaired functioning of SRY protein results in various sex development disorders.