E-Locus (yellow) and Em-Locus (mask)


The E-Locus is a region of your dog's DNA which controls whether your dog will only express the yellow pigment or whether they can express any of the other coat colours. 

The region has three alleles which have a dominance hierarchy:

Em > E > e

The Em allele is dominant and your dog only requires one copy of this allele to have a melanistic mask (darker muzzle). If your dog has a melanistic mask then they also have a coat colour controlled by the other regions (K-Locus, A-Locus, D-Locus and B-Locus), and the mask may not be visible on a darker coat colour. 

If your dog has anything other than the recessive e/e then their coat colour is decided by the alleles they have at the K-Locus, B-Locus, and A-Locus. 

If your dog has two copies of the recessive allele (e/e) then they will have a yellow coat. The colour spectrum produced here can vary from the palest Golden Retriever through to the rich red of an Irish Setter.

Also known as white, cream, yellow, apricot, gold, lemon, red and many more.

In order to be yellow your dog must be e/e at the E-Locus, anything other than this at the E-Locus and the coat colour will be controlled by the K-Locus, B-Locus, and A-Locus.

The melanistic mask and yellow colouration are caused by mutations in the MC1R gene with an order of dominance as outlined above.


Your results will be reported as one combination of the E-locus alleles with the following interpretations.

Em/Em - two copies black mask
Em/E - black mask, no yellow
Em/e - black mask, carrying yellow
E/E - no black mask, no yellow
E/e - no black mask, carrying yellow
e/e - no black mask, yellow

Scientific references:

Newton JM, Wilkie AL, Jordan SA, Metallinos DL, Holmes NG, Jackson IJ, and Barsh GS (2000) Melanocortin 1 receptor variation in the domestic dog. Mamm. Genome 11, 24-30

Schmutz SM and Berryere TG (2007) Genes affecting coat colour and pattern in domestic dogs: a review. Anim. Genet. 38, 539-549

Schmutz SM, Berryere TG, Ellinwood NM, Kerns JA, and Barsh GS (2003) MC1R studies in dogs with melanistic mask or brindle patterns. J. Hered 94, 69-73

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