Understanding Basic Horse Color Genetics

This calculator uses two fundamental gene pairs:

• Extension (E/e): Controls the production of black pigment. 'E' is dominant and allows black. 'ee' is recessive and restricts pigment to red, resulting in a chestnut/sorrel horse regardless of other genes.
• Agouti (A/a): Controls the *distribution* of black pigment. 'A' is dominant and pushes black pigment to the points (legs, mane, tail), creating a bay. 'aa' is recessive and allows black pigment to cover the whole body, creating a black horse (only if an 'E' allele is present).