Agouti aka ASIP gene interacts with the MC1R gene to control red and black pigment switching in most dogs.
Dog coat color is further complicated when other genes restrict agouti expression for example the dominant black gene-K. There are 4 known alleles of agouti. They are listed in order of Dominance.
1. ay- fawn or sable which expresses in shades of yellow to red with some dorsal black tipped hairs.
2. aw-Wild Sable expressing as banded hairs of yellow and black.
3. at-Black and Tan black expressing as dorsal hairs with tan hair on cheeks, eyebrows and undersides.
4. a-Recessive Black expressing as all black
The agouti test can help determine the color of dogs that have white patterns that may obscure the distribution of the colored pigment.
ay / ay 2 copies of fawn
ay / aw Dog is fawn and carries 1 copy of wild sable
ay / at Dog is fawn and carries 1 copy black and tan
ay / a Dog is fawn and carries 1 copy of recessive black
aw/ aw 2 copies of wild sable
aw/ at Dog is wild sable and carries 1 copy of black and tan
aw/ a Dog is wild sable and carries 1 copy of recessive black
at/ at 2 copies of for black and tan
at/ a Dog is black and tan and carries 1 copy of recessive black
a/a 2 copies of recessive black