Wednesday, September 2, 2015

Genetic anomaly

Most people heard or been told that calico cats are female.  This includes tortie and any version of cat that has both orange and black markings regardless of pattern. This is because in cats, the gene for black and the gene for orange are carried only on X chromosomes, but they cannot both occur on the same X chromosome.  Therefore to be calico a cat must be XX and that makes it a female.

Unless, it is an XXY male.  This syndrome is known as Klinefelter syndrome in humans and results in an a sterile, but anatomically and functionally normal male.  The same appears to be true in cats.

So while the vast majority of calico cats are female, you can never say all of them are.  A male calico is however, exceedingly rare as they not only have to be XXY but they also have to be genetically color coded to be a calico.  There could be more XXY cats out there but if they are any other cat color then no one would likely realize they have an extra chromosome.

Why bring this up today?  Because after 11 years of practice, we finally found one!


K-Koira said...

Wow, strange. I know we had a male calico when I was a kid, and I was told by someone that it couldn't possibly be a male calico because of that. But I know it was male, and it certainly was calico.

I've also heard, often in the same places, that solid orange, or orange and white, cats can only be males.

Lauren Miller said...

That is fascinating! Thanks for sharing!