![]() ![]() ![]() Subsequently, internal and external genitalia will follow the male pathway in the presence of androgens and anti-Müllerian hormone (AMH), or the female pathway in their absence. The presence or absence of primordial germ cells, of extragonadal origin, also has a sexually dimorphic relevance. Believed initially to be governed entirely by the presence or absence of the SRY gene on the Y chromosome, gonadal determination has proven to rely on a complex network of genes, whose balanced expression levels either activate the testis pathway and simultaneously repress the ovarian pathway or vice versa. Sex differentiation involves a series of events whereby the sexually indifferent gonads and genitalia progressively acquire male or female characteristics. However, 6 weeks elapse in humans before the first signs of sex differentiation are noticed. The chromosomal sex of the embryo is established at fertilization. ![]()
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