Sexual Differentiation

When does the development of sex organs begin?

Begins in week 5 of embryonic development.

When is sexual differentiation typically complete?

Around week 7–8 of pregnancy.

What are the gonadal primordia and how do they start out?

Early gonads are identical in all embryos; differentiation depends on genetic signals.

What determines genetic sex in the embryo?

The combination of sex chromosomes:
XX → female
XY → male

What is the role of the SRY gene?

Sex-determining Region of the Y chromosome; triggers development of testes.

What protein does the SRY gene encode?

TDF (Testis Determining Factor)

What happens in the absence of a functional SRY gene?

The embryo automatically develops female characteristics (ovaries).

Can someone with an XX karyotype develop male traits?

Yes — if the SRY gene is translocated onto the X chromosome, an XX male may result.

Can someone with an XY karyotype develop as female?

Yes — if the SRY gene is deleted or inactive, the embryo may develop as an XY female.

What explains the rare exceptions in sex differentiation?

The presence or absence of the SRY gene region on the Y chromosome (or its translocation).