Sexual differentiation of the embryo is normally determined by
A)the number of chromosomes,with males having 22 pairs and females having an extra pair of XX chromosomes.
B)the presence of two X chromosomes,which causes the primordial testes to degrade.
C)the presence of one Y chromosome,which causes the primordial ovaries to degrade.
D)the presence of the Y chromosome,which directs the undifferentiated gonads to develop into testes (when there is one X chromosome present as well).
E)hormones produced by the placenta.

Question

Quizplus · Accepted Answer

The presence of the Y chromosome is crucial in determining male sexual differentiation. The Y chromosome carries a gene called SRY, which directs the undifferentiated gonads to develop into testes. If there is at least one X chromosome present, the testes will produce male hormones that further promote male sexual development. In the absence of the Y chromosome, the gonads will develop into ovaries and female sexual differentiation will occur.

Sexual Differentiation of the Embryo Is Normally Determined by