The agouti gene (A)

Description: This gene is responsible for determining where the black coloring goes on the body of the horse, creating sealbrowns and bay horses.

Notes:

1. The effect of the agouti gene is visible only on the black horses (that have at least one B allele). 
2. Unlike all the other colors, the alleles of the Agouti gene have 4 possible values (instead of just dominant and recessive):
   
   1. a - recessive, will leave the horse completely black
   2. AT - creates seal browns
   3. A - creates bay horses
   4. A+ - responsible for the wild bay horses

Forms:

1. a a - Black
2. AT a  - Seal Brown
3. A a - Bay
4. A+ a - Wild Bay
5. a AT - Seal Brown
6. AT AT - Seal Brown
7. A AT - Bay
8. A+ AT - Bay
9. a A - Bay
10. AT A - Bay
11. A A - Bay
12. A+ A - Wild bay
13. a A+ - Wild bay
14. AT A+ - Wild bay
15. A A+ - Wild bay
16. A+ A+ - Wild bay