The alleles at the A locus are related to the production of agouti-signaling protein (ASIP) and determine whether an animal expresses an agouti appearance and, by controlling the distribution of pigment in individual hairs, what type of agouti. There are four known alleles that occur at the A locus: Ay = Fawn or sable (tan with black whiskers and varying amounts of black-tipped and/or all-black hairs dispersed throughout) - fawn typically referring to dogs with clearer tan and sable to those with more black shading aw = Wild-type agouti (each hair with 3-6 bands alternating black and tan) - also called wolf sable at = Tan point (black with tan patches on the face and underside) - including saddle tan (tan with a black saddle or blanket) a = Recessive black (black, inhibition of phaeomelanin) ayt = Recombinant fawn ( black with tan patches on the face and underside ) has been identified in numerous Tibetan Spaniels and a Tibetan Mastiff . Its hierarchical position is not yet understood. 
The alleles at the A locus are related to the production of agouti-signaling protein (ASIP) and determine whether an animal expresses an agouti appearance and, by controlling the distribution of pigment in individual hairs, what type of agouti. There are four known alleles that occur at the A locus: Ay = Fawn or sable (tan with black whiskers and varying amounts of black-tipped and/or all-black hairs dispersed throughout) - fawn typically referring to dogs with clearer tan and sable to those with more black shading aw = Wild-type agouti (each hair with 3-6 bands alternating black and tan) - also called wolf sable at = Tan point (black with tan patches on the face and underside) - including saddle tan (tan with a black saddle or blanket) a = Recessive black (black, inhibition of phaeomelanin) ayt = Recombinant fawn ( expresses a varied phenotype depending on the breed ) has been identified in numerous Tibetan Spaniels and individuals in other breeds, including the Dingo . Its hierarchical position is not yet understood. Agouti Series
R
black with tan patches on the face and underside
expresses a varied phenotype depending on the breed
R
a Tibetan Mastiff
individuals in other breeds, including the Dingo
A
Agouti Series