B Locus Australian Shepherd (B-LOCUS-AS)
Brown, Chocolate, Liver, Red, baus allele
Mutations in the TYRP1 gene are responsible for the presence of brown/chocolate/liver color in the coats, noses, and foot pads in many dog breeds. This coat color may be referred to as “red” in Australian Shepherds. In the Australian Shepherd breed, four separate and distinct mutations can occur in the TYRP1 gene which leads to a change in the production of the black pigment known as eumelanin. A dog can inherit any two of the four mutations which dilutes the black color pigment into a brown color within the dog’s coat, nose, and foot pads. A dog must have two copies of any of the four TYRP1 mutations to express brown/chocolate/liver color in their coat, nose, and foot pads. It is also important to note that any number of these mutations may be inherited on one of the two gene copies a dog inherits. The result provided by this test is capable of determining the presence/absence of the Australian Shepherd mutation but is unable to determine if this mutation resides on the same or different gene copy as the other three mutations. In a case where a dog possesses two or more mutations, the result is reported as “C” or “At Risk/Affected” (also known as “bb”). Whether the mutations reside on the same or different gene copies can be determined by looking at the color of the dog’s nose and foot pads. If the mutations exist on a single gene copy, the dog will exhibit a black nose and foot pads and can be thought of as a “B” or “Carrier/Not Affected” since all mutations exist in one gene copy. If the mutations reported exist on both gene copies, the dog will exhibit brown/chocolate/liver nose and foot pads and can be thought of as a “C” or “At Risk/Affected”.
Reading Your Results
These dogs have two copies of the normal gene, will have a black-based coat, black noses, and footpads, and will not pass the mutation to their offspring.
B. (CARRIER/NOT AFFECTED):
These dogs have one copy of the normal gene and one copy of the mutation associated with brown/chocolate/liver coloring. They will have a black-based coat, black nose, and footpads and will, if bred, pass the mutation to 50% of their offspring, on average.
C. (AT RISK/AFFECTED):
These dogs have two copies of the mutation associated with a brown/chocolate/liver coat which can result in a brown/chocolate/liver coat coloring that varies by breed and can be referred to as “red” in Australian Shepherds. Some dogs that carry two copies of this mutation may not show brown/chocolate/liver coat coloring and will have black noses and foot pads. Please see the test description for more information.
Hrckova Turnova E, Majchrakova Z, Bielikova M, Soltys K, Turna J, Dudas A. A novel mutation in the TYRP1 gene associated with brown coat color in the Australian Shepherd Dog Breed. Anim Genet. 2017 Oct; 48(5):626. [PubMed: 28497851]