The agouti gene, A/a, controls whether or not the tabby pattern is expressed.

"W" represents the middle yellow-white band locus and works with the agouti gene.

The agouti gene, A/a which codes for agouti signaling protein.

Horses with the normal agouti gene have the genotype A/A or A/a.

Therefore, if a dog appears clear red or fawn but has a mask, the agouti gene is responsible for all pheomelanic hairs.

With the agouti gene now in hand, scientists can begin exploring how the peptide influences the development of other parts of the body beyond coat coloring.

By contrast, horses which lack a functional agouti gene cannot produce such alternating bands, and thus have wholly black coats with no visible phaeomelanin.

The centers of the patterns are hollow-looking due to the agouti gene producing a "salt and pepper" look.

In contrast, tabby cats have an agouti gene that produces striping of the coat.

In domestic cats, inactivation of the agouti gene by a deletion mutation causes all-black coat color.