What is X inactivation in biology?

As you know, females have XX chromosome and males have XY chromosome. You would think that without any sort of adjustment that females will have 2x as much of all products on X-linked genes than males because of having 2 X chromosomes. However due to dosage compensation, females have an X chromosome inactivated and they carry the same amount of X-linked gene product as males. One of the mechanisms of dosage compensation is X-inactivation, which also occurs in Calico cats.

If dosage compensation did not take place, females would carry double the amount of x-linked gene products than males.

X inactivation, also known as lyonization, is a process by which one of the two X chromosomes in female mammals is randomly inactivated during early embryonic development. This ensures that females, like males, have only one functional copy of the X chromosome in each of their cells, balancing gene expression between the sexes.