Mailbag: Zorse pigmentation

Re: Horse-zebra hybrids

I know you saw the picture of the zebra horse in the NYT this morning. Are we SURE that hasn't been photoshopped? I mean, I know it is the NYT, but it makes me thinkk that I don't understand ANYTHING about genetics at all!

Yeah, apparently this particular one is unique.

The stripes come from patterning genes that activate the melanin pathway; the pattern gradient inhibits expression of a gene that synthesizes melanin. White spots occur when a different gene is turned off, on the same pathway. So the two combine – it’s like a palomino that has stripes instead of splotches, I guess.

I have a slide that shows a cattle-bison hybrid with similar spots, like a cow.