User:Iamnotabunny/sandbox

=Sabino and dominant white= Sabino and dominant white are a genetically and phenotypically related group of white patterns in horses. Specifically, they are the alleles of the KIT gene responsible for various coat colors ranging from fully white through sabino-type pinto patterns to white face and leg markings, although not all horses with these appearances have them for this reason.

Although initially there was a clear answer to which of the known alleles counted as "sabino" and which counted as "dominant white", further discoveries have made the distinction less clear. One proposal is that the term "dominant white" should be used just for those alleles thought to be non-viable when homozygous.

Sabino is a phenotype involving irregular patches of white and colored hairs.

These white patterns generally have a dominant or incomplete dominant mode of inheritance.

History of nomenclature
The first KIT allele discovered to affect horse coat color was named Sabino 1 or SB1, following nomenclature used by horse breeders. It has an incomplete dominant effect, in which one copy produces a sabino pinto pattern while two copies produce a fully white or almost fully white horse.

The next four alleles discovered had a different effect, that of dominant white. One copy causes a fully white horse, while a second copy appears to be nonviable. These alleles were named W1, W2, W3, and W4, following nomenclature used in mouse genetics.

The difference between sabino and dominant white was considered to be that sabino made the horse partially white and was viable in homozygous form, while dominant white made the horse fully white and was likely non-viable when homozygous. At that point in time, these alleles were neatly separated into the two groups by name, either "SB" for sabino or "W" for dominant white.

However, some of the alleles discovered since do not fit either of these definitions. For example, W5 makes horses only partially white, but is believed to be non-viable in homozygous form. The majority of the W5 horses initially studied were nearly to fully white, but these were later discovered to additionally have the W20 allele.

When W20 was discovered, which has only a subtle effect increasing the amount of white, it was given a name in the "W" series "to provide a simple and unambiguous nomenclature for future genetic testing applications." It is likely that all further alleles in this series will be given a "W" name, regardless of whether their phenotype is more similar to sabino or dominant white.