Wednesday 9 November 2011

A Ginger Female

Two is a little ginger kitten. Actually she isn't even that little anymore but she still is a she. When I first got Two, Kristen kept saying, "I thought ginger cats had to be boys" and I thought since she was a dog person she didn't know what she was talking about. Well, I took Two for her second vet visit a couple of weeks ago and the vet was very excited to see a female ginger cat since they are so rare. In fact the vet double checked the sex even though the previous vet had already confirmed. I decided to I should look into this female ginger thing.

In order to explain this we need to consider kitty genetics. All cats have 19 pairs of chromosomes, and like humans, cats have one pair of sex chromosomes. These are the ones that make them male or female and they also play an essential role in determining their colour. Like humans, in female cats, both sex chromosomes are X making females XX. Males are XY, the Y making them male. The gene which makes a cat ginger (or orange tabby) is located on the X chromosome. This gene is a recessive gene, meaning it will be overrode by other colours. So, to be ginger, a cat has to have ginger gene switched to "on" on ALL X chromosomes. For a male, this is not hard to come by, because males have only one X. But since females have two Xs then its harder to come by one that has an orange gene on each X. So about 75% of ginger cats are male, and 25% are female. It's just a matter of odds.

Turns out that Kristen was onto something. So it is uncommon but not really rare. However, I have learned to pay attention to Kristen's cat knowledge now. She had also mentioned something strange about calicoes having to be female. I thought I should look into this too.

It turns out that a ginger female is different than a calico (or tortoiseshell) male. To be calico, a cat MUST have two Xs. That is almost impossible for boys, as they are XY. That is why almost all calicoes are female. However, occasionally there is a rare genetic mutation that makes a cat XXY and it appears to be a boy. It can be calico, as it still has two Xs. Since it is a strange genetic mutation they usually end up being sterile.

So, Two is not a not a genetic "slip up" like calico males, she has just "beaten the odds" by being a ginger female.

1 comment:

Fae said...

I've heard this before as well - both that all (well, most) gingers are male and calicos are female. So far, this had proved true for every cat I'd met of those types. My calico kitty had a calico sister that looked nearly identical to her, they were born at the same time as two brothers... but the brothers were B&W and looked exactly alike. I figured that confirmed the theory that calicos are only female, being that the two girls looked SO much alike I would have expected any other kitten of the litter to be the same as them. But not males, apparently.