Gonadal Differentiation
Early in fetal life, germ cells migrate from structures known as yolk sacs to the genital ridge. By week 6, undifferentiated gonads consist of germ cells, supporting cells, and steroidogenic cells.
In a male, SRY and other genes induce differentiation of supporting cells into Sertoli cells and (indirectly) steroidogenic cells into Leydig cells to form testes, which become microscopically identifiable and begin to produce hormones by week 8. Germ cells become spermatogonia.
Without SRY, ovaries form during months 2-6. Failure of ovarian development in 45,X girls (Turner syndrome) implies that two functional copies of several Xp and Xq genes are needed. Germ cells become ovarian follicles. Supporting and steroidogenic cells become theca cells and granulosa cells, respectively.
Read more about this topic: Sexual Differentiation