Résumé
In mammals, sex is determined by chromosomal constitution: males have one X chromosome and one Y chromosome; females have two X chromosomes (reviewed by Good fellow and Darling, 1988). Analysis of individuals with unusual sex chromosome combinations has shown that the presence of the Y chromosome is crucial for male sex determination and absence of the Y chromosome results in female development (Ford et al., 1959; Welshons and Russell, 1959; Jacobs and Strong, 1959). The Y chromosome acts by inducing the undifferentiated fetal gonads to become testes and subsequent male sexual differentiation is controlled by testicular hormones (Jost et al., 1973; Josso et al., 1977). The Y chromosome gene, or genes, responsible for inducing testis development have been named testis determining factor (TDF) in humans and testis determining-Y chromosome (Tdy) in mouse.