page_title: Agouti coloration genetics
section_title: Dogs
hierarchical_section_title: Agouti coloration genetics / Dogs
caption_attribution_description: English: Bucuresti, Romania, acelasi dulau, frumos de Cotroceni
context_page_description: The agouti gene is responsible for variations in color in many species. Agouti works with extension to regulate the color of melanin which is produced in hairs. The agouti protein causes red to yellow pheomelanin to be produced, while the competing molecule α-MSH signals production of brown to black eumelanin. In wildtype mice, alternating cycles of agouti and α-MSH production cause agouti coloration. Each hair has bands of yellow which grew during agouti production, and black which grew during α-MSH production. Wildtype mice also have light-colored bellies. The hairs there are a creamy color the whole length because the agouti protein was produced the whole time the hairs were growing.
  In mice and other species, loss of function mutations generally cause a darker color, while gain of function mutations cause a yellower coat.
context_section_description: In dogs, the agouti gene is associated with various coat colors and patterns.
  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.
  Most texts suggest that the dominance hierarchy for the A locus alleles appears to be as follows: Aʸ > aʷ > aᵗ > a; however, research suggests the existence of pairwise dominance/recessiveness relationships in different families and not the existence of a single hierarchy in one family.
  Aʸ is incompletely dominant to aᵗ, so that heterozygous individuals have more black sabling, especially as puppies and Aʸaᵗ can resemble the aʷaʷ phenotype. Other genes also affect how much black is in the coat.
  aʷ is the only allele present in many Nordic spitzes, and is not present in most other breeds.
  aᵗ includes tan point and saddle tan, both of which look tan point at birth. Modifier genes in saddle tan puppies cause a gradual reduction of the black area until the saddle tan pattern is achieved.
  a is only present in a handful of breeds. Most black dogs are black due to a K locus allele.
caption: An agouti dog, also called wolf sable
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