Guide 2: Allele Dominance

Category: Genetics

The base color of any foal is determined by two primary genes: Extension (E) and Agouti (A). Understanding their dominance hierarchy is critical for predicting basic color outcomes.

Extension Gene (E/e)

Determines black vs. red pigment.

E (Dominant): Produces black pigment (Black/Bay base).
e (Recessive): No black pigment. e/e is always Chestnut (Red).

Agouti Gene (A/a)

Restricts black pigment to points.

A (Dominant): Restricts black (Bay base).
a (Recessive): No restriction. a/a (with E/-) is Black.

💡 Breeding Tip

If you want a guaranteed Chestnut foal, breed two parents that are both e/e. For a Black foal, ensure parents pass on the recessive a/a to hide Agouti.