Genetics of The Bruce

It’s Saturday (Sunday now that I’ve published it), but I feel like doing a little Friday Cat Blogging. I didn’t get to yesterday, though not for a lack of something to say.

I’m taking a graduate level genetics course this semester and low and behold what did we study Thursday night but the genetics of domestic cats… A whole evening spent talking about alleles, incomplete dominance, and epistasis. And looking at dozens of cat pictures.

Now I’ve mentioned before that The Bruce’s unique characteristics come in part from his Scottish Fold looks, namely a mutation which made his ears fold. I tend to talk less about his being half Siamese, since of course everybody knows what a Siamese looks like.

What I didn’t know until last night is that Siamese get their distinctive color because of mutations of their own. The dark areas of their fur are caused by a mutation in the gene that makes an enzyme necessary in the production of melanin. Melanin as you probably know serves as a dark pigment. (It’s the complete lack of it for example that results in albinism).

Here’s what’s so cool about this mutated Siamese enzyme. It’s temperature specific. The reason the extremities (legs, tail, and muzzle) are darker in Siamese is that they’re cooler than the trunk of the body. Were you to take a Siamese and put him in a refrigerator at 33 degrees for 6 months, you’d come back to find a black cat. If you left him outside the entire summer, his extremities would become much paler.

Interestingly, this same phenomenon occurs in other animals, like the Himalayan rabbit. Studies on this animal were what determined the temperature specific nature of this trait. You can fit the animals with a long term ice pack and get a black spot of fur underneath.

Pretty cool stuff.