or tyrosinase-related protein 1, is a protein that plays a role
in the synthesis of the pigment eumelanin. In the dominant form
of this gene, or the "B" allele, normal eumelanin is produced
in the coat, and the dog's coat appears black in color. A mutation
in the TYRP1 gene can occur causing a change in function which dilutes
the black color pigment to a brown color. This mutated gene is known
as the "b" allele. When a dog is homozygous for the mutation,
meaning he has 2 copies of the recessive allele, the dog's coat
color will be brown in color. This color can also be referred to
as liver, chocolate, or in some breeds, red.
TYRP1 is only associated with eumelanin, this mutation only has
an effect on dogs that are "EE" or "Ee" at the
E-locus. Dogs that are "ee" only produce phaeomelanin
in their coats, so a mutation at the B-locus will not have an effect
on their coat color. However, eumelanin is still produced in the
foot pads and noses of "ee" dogs, so the B-locus still
has an effect on these areas. Dogs that are "eebb" will
have a brown nose and foot pads, rather than black.
Genetics currently offers a test for the B-Locus to determine how
many copies of the recessive "b" allele a dog carries.
US for the B-allele test.
sample using buccal swabs provided by Animal Genetics. Ensure that
the dog has not eaten within a few hours of sample collection. Any
food particles can inhibit the test. Rub each of the swabs along
the inside of the dog's mouth for 10-15 seconds, and allow the swabs
to dry thoroughly. Label the provided envelope with the dog's name,
and place the swab inside it. Download and complete a submission
form for each sample and send along with payment to Animal Genetics
Results are given using
the following symbolic notation:
dog carries two copies of the dominant B allele. The dog will
have a black-based coat, and will always pass on the "B"
allele to any potential offspring. All offspring will also be
the dominant and recessive copies of the B allele are present.
The dog will have black-based coat, but carries the allele responsible
for the brown phenotype. The dog can pass on either allele to
of the recessive allele are present. The dog has a brown-based
coat, as well as a brown nose and foot pads, and will always
pass on the recessive allele to all potential offspring.