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E-Locus (Recessive Yellow, Melanistic Mask Allele)

Description:

MC1R, also known as the extension gene, controls production of pigment in melanocytes. The dominant form of the gene, the "E" allele, allows the dog to produce eumelanin, which is a black pigment. A mutation in the MC1R gene causes the pigment-producing cells to only produce phaeomelanin, which is a yellow pigment. This form of the gene is represented as the "e" allele. The "e" allele is recessive, meaning that a dog must have two copies of the MC1R mutation to express the solid yellow coat colour.


A third allele exists in the extension gene, Em which is also dominant. This causes the dog to have a black mask on their face, also known as a melanistic mask. This allele acts similarly to the E allele, in that it causes a black-based coat. Because it is dominant, a dog only needs one copy of the Em allele to express this trait. In solid black dogs with a copy of the Em allele, the mask is hidden. However, it can still pass on the melanistic mask to future offspring.


The "ee" genotype can vary in expression between different breeds. In some breeds, the difference between a black or brown dog and a yellow dog is obvious, such as in Labrador Retrievers. However, in other breeds, such as Cocker Spaniels, this difference may be more subtle. Other breeds express the "ee" phenotype as a red colour.


It is important to note that the extension gene is only one of four important genes in determining the coat colour of a canine. The dog's colour can vary greatly with different mutated alleles on other genes. Dogs that are "ee" will always be yellow. However, there is a great deal of variation of dogs that are "EE" or "Ee," depending on the B-Locus, A-Locus, K-Locus, and D-Locus.

BE

Be

bE

be

BE

BB/EE (pure for black)

BB/Ee (black carrying yellow)

Bb/EE (black carrying brown)

Bb/Ee (black carrying brown and yellow)

Be

BB/Ee (black carrying yellow)

BBee (pure for yellow, black nose)

Bb/Ee (black carrying brown and yellow)

Bb/ee (yellow carrying brown)

bE

BbEE (black carrying brown)

BbEe (black carrying brown and yellow)

bbEE (pure for brown)

bbEe (brown carrying yellow)

be

BbEe (black carrying brown and yellow)

Bbee (yellow carrying brown)

bbEe (brown carrying yellow)

bbee (brown-nosed yellow)

E Locus Testing:

The MC1R gene, or E Locus, has three possible forms: Black (E), melanistic mask (Em), and Yellow (ee). The E-Allele test determines how many copies of the recessive "e" alleles a dog carries. The Em-Allele test determines how many copies of the melanistic mask allele a dog carries.

Sample Type:

Animal Genetics accepts buccal swab, blood, and dewclaw samples for testing. Sample collection kits are available and can be ordered at Canine Test Now.

Testing is Relevant for the Following Breeds:

All breeds.

Results:

Animal Genetics offers DNA testing for both E and Em alleles. The genetic test verifies the presence of these mutations and presents results as one of the following:

E/e Allele Results:

EE Black The dog carries two copies of the dominant E allele. The dog will have a black-based coat, and will always pass on the "E" allele to any potential offspring.
Ee Black carries Yellow Both the dominant and recessive copies of the E allele are present. The dog will have a black-based coat, but carries the allele responsible for the yellow phenotype. The dog can pass on either allele to potential offspring.
ee Yellow Two copies of the recessive allele are present. The dog has a yellow coat, and will always pass on the recessive allele to all potential offspring.

Em-Allele Results:

Em/Em Black Mask The dog carries two copies of the melanistic mask allele. The dog has a melanistic mask, and will always pass on a copy of the Em allele to potential offspring. All offspring will also have a melanistic mask.
Em/n Black Mask One copy of the melanistic mask allele is present, and the dog will have a black mask. The dog has a 50% chance of passing on this allele to potential offspring.
n/n No Black Mask Dog tested negative for the melanistic mask allele. The dog will not have a black mask, and cannot pass a copy on to any offspring.