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White Hair Patterns - cont’d KIT GENE - The KIT gene is actually the locus where four white patterns are found. The known KIT genes are: Tobiano Roan Sabino Dominant White All of these white patterns are found at the KIT locus. This means that a horse can have only two of these genes present at a time, similar to how a horse can have only two types of Agouti present at a time or both Cream and Pearl present, but not two cream and one pearl. For example, a horse cannot be a Roan Tobiano Sabino. When a horse is carrying two of these KIT genes, they are considered “homozygous” for the KIT gene. This means that a Tobiano Sabino horse will always have either Tobiano foals or Sabino foals, never solid foals. This also means that a Homozygous Tobiano horse cannot also be a roan, sabino or dominant white and same with any of the other KIT genes. So in all reality, a Tobiano Roan horse’s genetics should be written as TRn instead of Tt, Rnrn. However due to the fact that this would become very complicated and confusing, we stick to the format of Tt, Rnrn as it is easier to read and understand. A website that demonstrates how KIT genes work in an easy-to-understand, visual way is:
Appaloosa Patterns LEOPARD COMPLEX & VARNISH ROAN - The ‘Leopard Complex’ was so named because scientists originally thought this gene was responsible for the spotting on breeds such as the Appaloosa, Pony of the Americas, Knabstruppe, etc. While they were partially correct - in that the LP complex is needed for the spotting pattern to appear on the coat - it was not the gene that made the spotting pattern like that of a leopard. We know now that the LP gene is responsible for the white hair pattern “Varnish Roan”. Varnish Roan is similar to the Classic Roan gene except that it is a progressive gene, meaning that the older the horse gets, the more roan hair it will get. Another difference between Roan and Varnish is that Varnish will also spread to the head and legs of the horse, unlike Classic Roans. All horses that have at least one LP gene will have some form of Varnish Roan. Other characteristics of the LP gene are mottled skin around the eye and muzzle of the horse, white sclera, and striped hooves. LP is an “Activator” gene as well. In order for an Appaloosa to be a Blanket, Snowcap, Leopard or Fewspot they must have at least one LP gene. Whether a horse is Leopard or Blanket or Fewspot or Snowcap depends on if they are heterozygous LP (Lplp) or Homozygous LP (LPLP).There is now a test available for the LP gene. PATN1 & PATN2 - While there is no test available for the different spotting patterns of the Appaloosa coat, it is believed there are two genes that create two classes of spotting; PATN1 and PATN2.   Horses with PATN1 are Spotted Leopards and Fewspot Leopards. Spotted Leopards have what appears to be a white body with colored spots similar to what a Dalmatian looks like. Spotted Leopards are heterozygous LP (Lplp) and may be heterozygous or homozygous PATN1. Fewspot Leopards appear nearly all white with a few small colored spots and sometimes colored patches around the neck/mane, tail, knees & hocks and elbow & flank area. Fewspot Leopards are homozygous LP (LPLP) and either heterozygous or homozygous PATN1. It should also be noted that sometimes Fewspot Leopards can be “suppressed” and end up looking like extensive Snowcaps. The white will be over the majority of the horse’s body and stop at the legs and neck or head, but while these horses look like Snowcaps, genetically they are Fewspots. PATN2 horses are Spotted Blankets and Snowcaps. Spotted Blankets have white on their rump extending over the hips and sometimes up the back with colored spots in the white. The rest of the horse is colored. Spotted Blankets are heterozygous LP and either heterozygous or homozygous PATN2. Snowcaps, like Spotted Blankets, have white over their rump extending over the hips and sometimes up the back; however they do not have spots on the white. These horses are homozygous LP and either heterozygous or homozygous PATN2 Spotted Leopard: Lplp + PATN1 (heterozygous LP) Fewspot Leopard: LpLp + PATN1 (homozygous LP) Spotted Blanket: Lplp + PATN2 (heterozygous LP) Snowcap: LpLp + PATN2 (homozygous LP)