[Genetic mechanism of human sex differentiation].

The genetic mechanism controlling sexual differentiation had remained unknown for a long time. Karyotype analysis of sex-inverted patients or individuals with ambiguous sexual differentiation has enabled the localization and identification of genes involved. It is currently known that the SRY gene is responsible for the initiation of a cascade reaction leading to male differentiation of the primitive gonad. SRY is a +/- 820 base pairs gene located on the small arm of the Y chromosome, more precisely within the 1A1 alpha sub-segment. Although a few other genes are known to be involved in the downstream regulation of SRY, their precise mode of action is yet unknown.