Figure 1. Typical male and female sex determination and differentiation occur during fetal life. The presence of the Y chromosome in the karyotype and the SRY gene (sex-determining region Y gene) are the primary determinants of male sex development. The SRY gene initiates a cascade that leads to the development of testes from bipotential gonads. Testosterone and Anti Mullerian Hormone (AMH) are secreted by testicular cells, which masculinize the Wolffian (mesonephric) duct and cause the regression of the Mullerian (paramesonephric) duct, respectively. Dihydrotestosterone (DHT), produced by the 5-alpha reduction of testosterone, plays a major role in male external genital development and prostate formation. The absence of the SRY gene on the Y chromosome is the primary factor for the induction of the female sex, and the development of the uterus, fallopian tubes, cervix and upper vagina from the Mullerian duct.