Question

If Orange hair is Recessive and Black hair is Dominant in cats, how do calico cats have both? Why isn't black fur expressed only?

Answer 1

Explanation and Answer:

Calico cats are a fascinating example of genetics in action. The black and orange patches of fur that characterize these cats are a result of a genetic phenomenon called "X-chromosome inactivation"12.

In cats, the gene that dictates fur color is located on the X chromosome2. Nearly all calico cats are female, so they have two X chromosomes12. One X chromosome can carry the gene for black fur, and the other can carry the gene for orange fur3.

During the embryonic development of every female mammal, one of the X chromosomes in each cell becomes inactive, a process known as "lyonization"4. This inactivation is random, meaning that in some cells, the X chromosome carrying the gene for black fur is active, and in others, the X chromosome carrying the gene for orange fur is active14. This results in a patchwork of black and orange fur1.

Calico cats also have patches of white fur due to a genetic condition called “piebalding”, which affects a skin cell’s ability to produce the pigment that causes color4.

So, the presence of both black and orange fur in calico cats is not about dominance or recessiveness of the genes, but rather a unique interplay of genetic mechanisms. Fascinating, isn’t it?

Answer 2

The genes responsible for coat color are located on the X chromosome. Female cats have two X chromosomes (XX), while males have one X and one Y chromosome (XY). The specific pattern of fur color in calico cats is a result of X-inactivation during embryonic development. In each cell, one X chromosome is randomly inactivated, leading to patches of cells expressing the genes for black fur and other patches expressing the genes for orange fur.

Step-by-step explanation:

calico cats can display a mix of black and orange fur, creating the distinctive patchwork pattern. This phenomenon is more commonly observed in female cats due to their two X chromosomes.