Question

What is the cellular reason for X-inactivation?

1) To reduce the amount of nondisjunction during meiosis
2) To increase the amount of nondisjunction during meiosis
3) To prevent the formation of gametes
4) To increase the genetic diversity

Answer 1

X-inactivation is a compensatory mechanism in female mammals that occurs early in development to ensure dosage compensation, by inactivating one of the two X chromosomes to equalize gene expression between the sexes.

Step-by-step explanation:

The cellular reason for X-inactivation is to ensure that females, who have two X chromosomes, do not express double the amount of X chromosome genetic information compared to males, who have only one X chromosome. This process is a compensatory mechanism that happens early in the development of female embryos, where one of the two X chromosomes in each cell becomes inactivated by condensing into a Barr body.

The inactivation of the X chromosome is random—with either the maternally or paternally derived X becoming inactive—but once inactivation occurs, all cells derived from that one will have the same inactive X chromosome. This leads to dosage compensation, where females have the functional equivalent of one X chromosome, like males.

Therefore, the correct answer is none of the options provided.