Originally Posted by AriatChick772
Can someone explain to me how this horse is a registered thoroughbred? Wouldn't you have to cross breed to get that color?
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This particular colour is caused by a mutation on the KIT locus. The KIT locus is one of the less "stable" loci, which has many different mutations (at least 11 DW mutations, tobiano, roan, at least 2 sabino, and maybe rabicano is there too, so possibly around 20 mutations). So the colour occurred by mutation at some point in the horse's family tree. I can't find the paper on dominant white, but the Puchilingui line of TBs has definitely got dominant white, and I presume that he (Puchi) is the case zero, although I am basing that assumption on nothing except that the line is named after him.