The Agouti gene (ASIP gene) is responsible for the production of a protein that regulates the distribution of black pigment (eumelanin) within the hair shaft. This gene is also known as the A-locus and is responsible for ticking and causes the individual hairs to have bands of light and heavy pigmentation. The agouti band can be seen in both black-based and red-based colours. The Coat Colour Agouti test (K757) tests for the genetic status of the A-locus. The A-locus has two variants (alleles). The allele A is dominant and produces ticked coat, hair shafts with alternating bands of yellow and black colour, ending with black tips (similar to the coat of a wild mouse or rabbit).The recessive allele produces a cat that is “self”coloured (solid). Only when the cat has two copies of the recessive allele a the coat colour is solid.
Another system of pigmentation in cats produces the tabby patterns of dark stripes interspersed with the lighter agouti tipped hairs. Hairs in the darker stripes do not have the shift between black and yellow pigment production and remain uniformly dark. The effect of the agouti protein on orange pigment is limited, thus tabby striping may still be seen on cats that are a/a for agouti.
The Coat Colour Agouti test (A-Locus) enclose the following results:
| A-locus | Coat Colour |
|---|---|
| A/A | Agouti coat colour |
| A/a | Agouti coat colour |
| a/a | Solid, “Self” coloured |
