In humans, clear gender differentiation occurs, not at fertilization, but after the second month of gestation. What is the first event of this differentiation?
A) formation of testosterone in male embryos
B) formation of estrogens in female embryos
C) anatomical differentiation of a penis in male embryos
D) activation of SRY in male embryos and masculinization of the gonads
E) activation of SRY in females and feminization of the gonads

Question

Quizplus · Accepted Answer

The first event of gender differentiation in humans is the activation of SRY (sex-determining region on the Y chromosome) in male embryos, which leads to the development of testes and the production of testosterone. This subsequently masculinizes the gonads and causes the development of male external genitalia. This occurs around 6-8 weeks of gestation.

In Humans, Clear Gender Differentiation Occurs, Not at Fertilization, but After