Description

The coat color of all horses 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, sorrel to gray, every single one of them begins with one of these two possible base pigments (red or black).  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.   

Horses that are bay, black, grullo, buckskin, black/blue roan, etc. are black pigmented horses that carry at least one copy of the Black Factor (E) allele.  The black (E) allele of the Extension gene is dominant and causes a black pigmented base both in the heterozygous (Ee) and homozygous (EE) state.  A horse that is heterozygous for Red/Black Factor means that it carries one copy of the black allele (E) and one copy of the red allele (e).  A horse that is heterozygous for red/black factor can pass on either red or black pigment to its foals.  A homozygous black (EE) horse means that it carries two copies of the black allele (EE).  A homozygous black horse will always produce black based foals regardless of it’s mate. 

Horses that are chestnut or sorrel, palomino, red dun, red roan, etc. are red pigmented 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 parent have passed on a copy of the red (e) allele.

Why test for Red/Black Factor?

Often breeders of black horses will want to test for Red Factor to determine if the horse is homozygous for black (EE). Homozygous black horses will always throw black as a base pigment. Thus, the resulting offspring will always be black based and could never be red such as a chestnut or sorrel. Other reasons to test for Red Factor would be to verify that a horse has a red pigment base. Cremello and Palomino horses are homozygous for Red Factor (ee).

Red/Black Factor Testing

Animal Genetics offers DNA testing for the Red/Black Factor (Extension) gene.

Cost

$25.00 US per sample.

Sample Collection

Collect sample by pulling (not cutting) 20-30 mane or tail hairs with roots attached. It is important that you pull the hairs and confirm that the actual root of the hair is being collected. The root contains the genetic material of your horse that is needed for DNA testing. Therefore, cut hairs do not provide an adequate sample of your horse. Place the collected hairs of each horse in a separate zip-lock bag labeling the bags accordingly with the horses name or identification number. Download and complete a submission form for each sample and send along with payment to Animal Genetics for testing.

Results

Results are given using the following symbolic notation: