Coat Patterns

Merle

Alternative Names: Dapple, Blue

Merle Photo

The Merle variant causes a patchy coat pattern common in many herding breeds. Each dog's pattern is unique. On a black dog, areas of black and silver will be seen, or on a chocolate dog, areas of brown and beige. It can occur in combination with many other coat patterns, and can cause blue eyes or a fully or partly pink nose. The Merle variant is found in the PMEL gene (known as the M locus).

More Info

Did you know?

All Merle dogs are thought to have descended from a single Collie-type dog with the variant, that lived in Britain before 1870. Merle primarily affects dark pigment appearance, so in red dogs, the coat color mottling with be subtle. In the Catahoula Leopard Dog breed in which merle is common, blue eyes are called "glass eyes" and when partially blue, are called "cracked" eyes. The merle variant length can vary, and impacts whether the standard Merle pattern is seen. Occasionally, the merle variant can be elongated, called harlequin merle. This is a different gene than the Harlequin variant seen in the Great Dane.

How it works

Most dogs with one copy of the Merle variant will show Merle patterning. Most dogs with two copies will be mostly white, but in some cases will show Merle patterning. Some dogs with this variant will not show the Merle pattern. This is because the Merle variant can sometimes be shortened (known as cryptic or atypical Merle), and these forms do not have an effect on appearance.

Health implications

A dog that inherits two copies of merle is called a "double merle" and, unless atypical or cryptic merle variants are present, this poses a significant health risk to the dog. Double merle dogs are often deaf and blind at birth, and may also have abnormally small eyes (microphthalmia). For this reason, two visibly merle dogs should never be bred together.

Prevalence

1 in 19 dogs

has one or more copy of this genetic variant in our testing.

Technical Details

Gene PMEL
Also Called Merle (M) Locus
Variant Insertion
Chromosome 10
Coordinate 292,705

All coordinates reference CanFam3.1

References & Credit

Credit to our scientific colleagues:

Clark, L. A., Wahl, J. M., Rees, C. A., & Murphy, K. E. (2006). Retrotransposon insertion in SILV is responsible for merle patterning of the domestic dog. Proceedings of the National Academy of Sciences of the United States of America, 103(5), 1376–1381. View the article