How does the presence of the Y chromosome influence sexual development?

The presence of the Y chromosome is crucial in determining male sexual development due to the SRY (Sex-determining Region Y) gene it carries. This gene is responsible for initiating the process of male sex differentiation.

When the Y chromosome is present, the SRY gene activates the pathway that leads to the development of male sexual characteristics. It triggers the formation of testes, which secrete testosterone and other hormones that promote the development of male secondary sexual characteristics. In the absence of the Y chromosome, the default pathway is to develop female characteristics, which leads to the formation of ovaries and the development of female genitalia.

Thus, the Y chromosome fundamentally stimulates the formation of male sex organs, making it a pivotal factor in sexual differentiation. This is why the choice stating that it stimulates the formation of male sex organs is correct.