A-AT Locus (A-AT-LOCUS)
Agouti, Black and Tan, Tricolor, Tan Points
The A Locus (agouti series) interacts closely with the E, K, and B Loci which can lead to a dog’s overall coat color and pattern. A-Locus mutations are only expressed if the dog is “Clear” or “Carrier” at the E locus and “Clear” at the K-KB locus. Four potential mutations at the A Locus can each have a different effect on coat color. The mutations are known as A-AY, A-AW, A-AT, and A-A and can determine whether a dog is a Carrier of sable/fawn, wolf sable/gray, black and tan/tricolor/tan points coloration or a recessive form of a solid black or bicolor coat color. The A-AT mutation produces a coat pattern typically referred to as “tricolor” or “black-and-tan”. For dogs that are “Clear” at the K-KB Locus and A-AW and have two copies of the A-AT mutation or one copy of the A-AT mutation and one copy of the A-A mutation will express this coat pattern. This also means a dog that appears tricolor or black-and-tan can carry the A-A allele and would not express recessive black. This is due to the fact that the A-Locus alleles are expressed in a hierarchical manner with A-AY being dominant to and expressed over A-AW, A-AT, and A-A. It is important to note that the dog’s coat color is also dependent on the dog’s genotypes at E, K, and B Locus among others.
Reading Your Results
A. (CLEAR/NORMAL):
These dogs have two copies of the normal gene and the effect of A Locus on their coat color can be determined by testing the A-A Locus. They will also not pass this mutation to any of their offspring.
B. (CARRIER/AFFECTED):
These dogs have one copy of the normal gene and one copy of the mutation associated with tricolor or black-and-tan. They will exhibit a tricolor or black-and-tan coat pattern in the absence of the A-AY and A-AW mutation. However, this dog’s coat color is also dependent on the E, K, and B Locus genes. They 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 and will develop a tricolor or black-and-tan coat pattern due to the A-AT locus mutation and will pass this mutation to 100% of their offspring. However, this dog’s coat color is also dependent on the E, K, and B Locus genes.
Additional Details
Inheritances
Complex order of dominance with other A Locus mutations (AY > AW > AT > A) and also depends on results for E, K, and B Locus mutations.
Affected gene
ASIP
Chromosome
Ch. 24
Mutation
SINE Insertion Of Approximately 239 Base Pairs In Intron 1a
Publication:
Dreger DL, Schmutz SM. A SINE insertion causes the black-and-tan and saddle tan phenotypes in domestic dogs. J Hered. 2011 Sep-Oct; 102 Suppl 1:S11-8. [PubMed: 21846741]
