18 March 2015

Revealed: Why Calico Cats Are Almost Always Female

Image via Erica Zabowski

Did you know that calico cats are almost always female?

Discovered on Today I Found Out, this strange but true fact means that only one in roughly 3,000 calico cats are male, and it’s all due to genetics.

To start things off, here’s a quick science recap: females have two X chromosomes and males have one X and one Y chromosome. In cats, the X chromosome determines black or orange fur—a cat needs two X chromosomes to be considered a calico.

Male cats receive the X chromosome from their mothers and that alone determines the color of their fur. Female cats receive an X chromosome from both their mother and father.

Since each cell only requires one X chromosome, one of the two chromosomes gets deactivated when the feline embryo is developing.

However, some cells might switch on the X chromosome from the mother, while other cells might turn on the X chromosome from the father.

If the X chromosomes are coded to black and orange respectively, this results in the two colors combining to form black and orange patches.

A separate gene causes the occurrence of white fur, giving calico cats their distinctive tri-color, or tortoiseshell-and-white coat.

Since calico cats need two X chromosomes and female cats have those, how do male calico cats exist?

Male calico cats inherit an extra X chromosome which makes their genetic make-up XXY. This is similar to a human condition called Klinefelter Syndrome which causes sterility in men.

Head over here to read the full post.

[via Neatorama and Today I Found Out, image via Erica Zabowski]