Question

The female calico cat has a particular coat coloring because each cell contains _____ active X chromosome(s).

a) One
b) Two
c) Three
d) Four

Answer 1

Each cell of a female calico cat contains one active X chromosome due to X inactivation, leading to their distinct coat coloring. The option (A) is correct.

Step-by-step explanation:

The female calico cat has a particular coat coloring because each cell contains one active X chromosome. This phenomenon is due to a process called X inactivation, which occurs early in the embryonic development of female mammals. Since the gene for coat color is located on the X chromosome, in female cats, one of the two X chromosomes is randomly inactivated in each cell.

As a result, the tortoise or calico pattern emerges if the female cat has two different alleles (versions) for coat color. This is why you can often identify a tortoiseshell cat as female, as male cats, which have only one X chromosome, do not present such variegation in coat color. Therefore, option (A) is correct.