Description
Equine coat color is built on one of two possible base pigments: red or black. The extension gene controls the production of this base pigment [red or black]. All of the coat colors we see today, from white to black and sorrel- every single one of them begins with either a red or black base pigment. All horses will have the genetics for black or red pigment, regardless of their physical appearance. There are a number of dilutions patterns and modifiers which a horse can carry that affect the base pigment of a horse.
Chestnut or Sorrel- ee/aa OR ee/Aa OR ee/AA - Horses that are red based horses and must carry two copies of the Red Factor [e] allele. The red [e] allele of the Extension gene is recessive and will only cause red pigmentation when the horse carries two copies of this allele; this is referred to as Homozygous red [ee]. Therefore, a red based foal results when both parents have passed on a copy of the red [e] allele.
From Left to Right; Sandy Chestnut, Standard Chestnut, Liver Chestnut, Black Chestnut