E Locus (E LOCUS)

A mutation in the MC1R gene (E locus) is responsible for the presence of yellow to red coats in many different domestic dog breeds. The normal form of the gene (“E” allele) allows the dog to produce a black pigment called Eumelanin. A mutation in the MC1R gene causes the pigment-producing cells to generate a yellow pigment called Pheomelanin. A dog must have two copies of the MC1R recessive mutation (represented as the “e” allele) to express the solid yellow coat color. This “ee” genotype can vary in expression ranging from yellow or red coloring to more subtle differences (apricot, cream, or white) depending on the breed.  The genetic cause of what is termed “Red” in some breeds (Dobermans and Australian Shepherds) is actually brown/liver/chocolate and due to a mutation in B Locus and not E Locus.

While this test will detect yellow to red coats in most breeds, it is important to note there are two breed specific mutations that are not detected by this test. The first mutation not detected by this test is known as “e2” and can be found in Australian Cattle Dogs. The second breed specific mutation not detected by this test is known as “e3” and can be found in the Husky breed. There are also additional mutations in this gene that result in a Melanistic Mask (“Em”) and Grizzle (“Eg”) that are also not detected by this test.