ABSTRACT
Early gonadal differentiation occurs in the urogenital ridge and is regulated by at least two genes, ZFY and SRY, located on the short arm of the Y chromosome. The SRY (sex-determining region of Y) gene encodes for a testis-specific deoxyribonucleic acid (DNA)-binding protein that stimulates development of the embryonic gonad towards a testis. Subsequent hormone production, specifically testosterone and Müllerian inhibiting substance (MIS), by the fetal testis controls a cascade of secondary changes leading to virilization of the basic female external genitalia and influencing the process of testicular descent (Figure 36.1).
