Leopard complex

The leopard complex is a group of genetically-related coat patterns in horses. These patterns range from progressive increases in interspersed white hair similar to graying or roan to distinctive, Dalmatian-like leopard spots on a white coat. Secondary characteristics associated with the leopard complex include a white sclera around the eye, striped hooves and mottled skin. The leopard complex genes are also linked to abnormalities in the eyes and vision. These patterns are most closely identified with the Appaloosa horse breed, though its presence in breeds from Asia to western Europe has indicated that it is due to a very ancient mutation.

Coat patterns in the leopard complex range from being hardly distinguishable from an unaffected coat, to nearly pure white. Unlike most other spotting patterns, the spotting and especially the white regions associated with the leopard complex tend to be symmetrical and originate over the hips. Furthermore, a certain amount of this inherited white patterning is present at birth. The amount of white, even if none is present at birth, often grows throughout the horse's life by gradual "roaning" which is not related to graying or true roan. Colored spots reflect the underlying coat color, be it black, chestnut, gray, or silver dun-buckskin. A number of factors, each separately, genetically controlled, interact to produce familiar patterns such as "snowflake," "leopard," and "fewspot".

A single, incomplete dominant gene (Lp) controls the presence of leopard-spotting in horses. A dominant gene requires only a single copy to produce an affected phenotype; an incomplete dominant gene produces a different result depending on whether one or two copies are present. A horse's genotype may be lp/lp (homozygous recessive), Lp/lp (heterozygous), or Lp/Lp (homozygous dominant). Horses without a dominant Lp gene do not exhibit leopard-complex traits, and cannot produce offspring with the Lp gene unless it is contributed by the other parent. Such horses are termed "non-characteristic" among Appaloosa horse aficionados. Horses with at least one Lp gene possess, at the very least, leopard-complex "characteristics":

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