But remember a horse has to do more than just test for At. At is recessive to all other alleles on the Agouti Locus. The horse would have to be AtAt or positive At and (a) being Ata in order to be brown.
No it is not. At is dominant over A. If you have a horse test AtA you will have a brown horse.
Hierarchy of interactions between Agouti alleles:
Bay A > At > a
(bay A is dominant over At and 'a'; At is dominant over 'a')
Expected base colors of an E/e or E/E horse:
A/A, A/At, A/a = bay
At/At, At/a = seal brown
A/a = black
Pulled from the DNA test site that NDAppy posted. This is also on almost every other horse color or genetic site I've see so far as well. Where did you read that At was dominant? I'm curious to read this..
