Extension is the gene that controls whether a horse is black based (E) or red based (e), the only two colors that are true base colors. Every other horse color is a caused by a modifier or dilution. As I said in my last post black (E) is dominant over red (e). A black based horses genetic composition will be either Ee or EE, and a red based horses genetic composition will always be ee.
Here are some examples of black horses
This is Aloha. He is a black Mecklenburg stallion, standing at Gray Fox Farms. His genetic composition is Ee.
This is Redwine he is a Hannoverian stallion, who also stands at Gray Fox Farms, and also has a genetic composition of Ee.
This is Zorro. A homozygous black (EE) Friesian Stallion standing at Mon Cheval.
This is Sjoerd, another homozygous black (EE) Friesian stallion, standing at Three Day Ranch.
And here are the red based horses.
This is AC's Painted Lace. She, like all red bases is ee. (Photo copyright ACCPhotography)
This is the grand prix show jumping stallion Baloubet du Rouet. He of course is ee.
This is Couleur Rubin, a chestnut (ee) Oldenburg stallion
This is Don Schufro, a dark or liver chestnut stallion
Within the next week or so, I will be doing at least one other post on the Agouti modifier, and hopefully the Cream dilution as well!! See you then!