| Description:
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Certain breeds of
dogs that have a tan, yellow, fawn, or other pale coat
colour over most of their body may also have a black,
brown or grey mask over their muzzle. This black muzzle
can sometimes extend up over their ears. Breeds that
have such a black mask include the Akita, Bullmastiff,
Boxer, German Shepherd, Great Dane, Greyhound, Keeshound,
Leonberger, Mastiff, Pekinese, Pug, Rhodesian Ridgeback,
Sloughi, Tibetan Spaniel, and Whippet. Studies have
determined that variation in a gene known as MC1R is
responsible for the black mask observed in these breeds.
Dogs that carry two mutated copies of this gene (recessive)
produce coat colours such as yellow, gold, apricot,
or red. Dogs that carry the dominant form of this gene
have a black mask. The mechanism by which the black
mask is formed in affected breeds involves an interaction
between the MC1R or E gene with the agouti protein and
melanocyte-stimulating hormone. The dominant MC1R gene
allows agouti to bind to its receptor some of the time
which results in the synthesis of the fawn pigment throughout
the body, while the melanocyte-stimulating hormone can
instead bind on the face and produce the melanin pigment.
The Melanin pigment can be black, grey or brown and
therefore the term "melanistic" mask includes
all these types of masks. Because of this, any phaeomelanin-pigmented
dog (i.e. yellow, fawn, red, cream) is due to an agouti
genotype. Such dogs cannot be "e/e" at MC1R
because a dominant E is required for the production
of a melanistic mask.
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| DNA Test: |
The discovery of genes
associated with canine masks has lead to the development
of a DNA based test that detects the presence of these
masks in Great Danes, Greyhounds, and Whippets. In Great
Danes, the black mask is inherited as a dominant trait.
It is not evident on black dogs but they may carry this
trait too. In Greyhounds and Whippets, the black mask
is also inherited as a dominant trait. It is not evident
on black dogs or dogs with white markings on the muzzle
but they may carry this trait too. In dogs that have
dilute colours, such as grey or grey brindle, the mask
will be grey and difficult to detect. This test provides
breeders with a percentage (i.e. 0%, 50%, 100%) that
represents the probability that the pups will have a
mask from a tested parent.
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