The inheritance of the leopard complex of spotting patterns in horses.

This research study investigates the inheritance of a variety of white spotting patterns on horses, collectively known as the leopard complex. The researchers used a sample of 22 horses from different breeds and analysed the patterns on their 270 offspring, suggesting these patterns can be attributed to a single dominant allele.

Understanding the leopard complex

• The white spotting patterns on horses that constitute the leopard complex encompass a range of different patterns. These include the leopard, few-spot leopard, blanket, blanket with spots, varnish roan (or marble), snowflake, frosted, speckled, and mottled patterns.
• Horses that display any of these patterns can produce foals with different patterns, even when mated with horses that lack these patterns.

The significance of the Lp allele

• By studying 22 horses from different breeds, namely the Welsh Pony, Noriker, Appaloosa, and Pony of the Americas breeds, and their 270 offspring, the researchers found the distribution of these patterns consistent with the influence of a single, dominant allele.
• The researchers designate this allele as ‘Lp’, stemming from previous research into the leopard pattern – one of the patterns involved in the complex.
• Horses which possess just one copy of this allele (heterozygotes) have lesser markings than those with two copies (homozygotes), but there is some overlap between these two groups in terms of marking extent.

Varying degrees of expression and pattern differences

• Differences in the specific type and extent of the pattern displayed by a horse are suggested as being related to the varying ways in which this ‘Lp’ allele is expressed.
• Thus, the workings of this dominant leopard pattern gene seem to involve a more nuanced manifestation than simple dominance, with the genetic expression levels influencing the specific phenotype visible on the horse.