Agouti

## Summary

The **Agouti** gene controls the distribution of black pigment. When an agouti allele is present, black pigmentation is restricted to a horse's points: legs, mane, tail, and rims of the ears. A horse must be black(Ee or EE) to show agouti. Dominant black horses are not effected by agouti.
In Horse Isle 3, agouti has 4 alleles: **Ap**, **A**, **at**, and **a**. Ap produces brown or wild bay, A produces brown or bay, at produces seal brown, and a produces black.

## Wild Bay

Wild bay, **Ap**, is the complete dominant allele of agouti. Being the complete dominant allele, Ap can be either homozygous(ApAp) or heterozygous(Ap\_) to be expressed, however it requires a horse's extension gene to be heterozygous(Ee) to be expressed as wild bay, as homozygous black will be a brown horse. When we see a wild bay horse, we know that it is heterozygous black(Ee) and that it has at least one Ap allele, but it is impossible to know, without a genetics test, if it is homozygous Ap or heterozygous Ap. When we know that at least one allele is Ap, we can simply list it's gene as Ap\_, where the \_ signifies any other allele in the agouti genotype.

* Ee + ApAp = Wild Bay
* Ee + ApA/AAp = Wild Bay
* Ee + Apat/atAp = Wild Bay
* Ee + Apa/aAp = Wild Bay

There are 6 shades of wild bay: blood, red, wild bay, bright, golden, and sandy.

GeneWildBayBlood.pngBlood Wild BayRed Wild BayWild BayGeneWildBayBright.pngBright Wild BayGolden Wild BaySandy Wild Bay

## Bay

Bay, **A**, is a dominant allele of agouti, recessive only to Ap. Being recessive only to Ap, we know that a bay horse can be either homozygous(AA) or heterozygous(Aat, Aa) to be expressed, however it requires a horse's extension gene to be heterozygous(Ee) to be expressed as bay, as homozygous black will be a brown horse. When we see a bay horse, we know that it is heterozygous black(Ee) and that it has at least one A allele without an Ap allele, but it is impossible to know, without a genetics test, if it is homozygous A or heterozygous A.

* Ee + AA = Bay
* Ee + Aat/atA = Bay
* Ee + Aa/aA = Bay

There are 6 shades of bay: blood, red, bay, bright, golden, and sandy.

GeneBayBlood.pngBlood BayRed BayBayBright BayGolden BayGeneBaySandy.pngSandy Bay

## Brown

Brown is produced by both **Ap** and **A** when a horse is homozygous black(EE). When we see a brown horse, we know that it is homozygous black, but we do not know if it is Ap, A, or if it is homozygous or heterozygous.

* EE + ApAp = Brown
* EE + ApA/AAp = Brown
* EE + Apat/atAp = Brown
* EE + Apa/aAp = Brown
* EE + AA = Brown
* EE + Aat/atA = Brown
* EE + Aa/aA = Brown

There are 5 shades of brown: dark, sepia, brown, chocolate, and auburn.

Dark BrownSepia BrownBrownChocolate BrownAuburn Brown

## Seal Brown

Seal brown, **at**, is the third and recessive allele, dominant only to a. Being recessive, we know that if we see a seal brown horse that it is either homozygous(atat) or heterozygous(ata), but without a genetics test, to know if it is homozygous at or heterozygous at. Unlike Ap and A, seal brown is expressed whether the horse is homozygous or heterozygous black.

* EE/Ee + atat = seal brown
* EE/Ee + ata/aat = seal brown

There are 3 shades of seal brown: ebony, seal brown, and burgundy.

Ebony Seal BrownSeal BrownBurgundy Seal Brown