Red/Black Factor

Description

Equine coat color is built on one of two base pigments: red or black. The Extension gene (MC1R) controls which of these a horse produces. Every coat color, from white to black and sorrel to gray, begins with a red or black base, and every horse carries alleles for this gene regardless of how it looks. Dilutions, patterns, and modifiers acting on that base pigment produce the wide variety of colors seen in horses.

Horses that are bay, black, grullo, buckskin, blue roan, or otherwise black-pigmented carry at least one copy of the black (E) allele. Black is dominant, so a single copy is enough to give a black-based coat, and a horse produces black pigment whether it is heterozygous (E/e) or homozygous (E/E). A heterozygous horse carries one black allele and one red allele and can pass either to its foals. A homozygous black horse (E/E) will always produce black-based foals regardless of its mate.

Horses that are chestnut or sorrel, palomino, red dun, red roan, or otherwise red-pigmented carry two copies of the red (e) allele. Red is recessive, so it produces a red-based coat only when both copies are present (e/e). A red-based foal results when both parents pass on a copy of the red allele, so at least one parent must be red-based or a heterozygous black horse (E/e). When breeding to a heterozygous black horse, each foal has a 50% chance of inheriting the black allele and being black-based.

This test determines the horse’s base pigment and whether a black-based horse carries a hidden red allele. It does not determine whether black pigment is distributed evenly or restricted to the points, which is controlled by Agouti. Testing Red/Black Factor together with Agouti gives a complete picture of the horse’s base color.

Possible results

Breeds Affected

All breeds

Reference

Mutations in the agouti (ASIP), the extension (MC1R), and the brown (TYRP1) loci and their association to coat color phenotypes in horses (Equus caballus).

Related Tests

• Agouti — determines whether black pigment covers the body or only the points
• Cream Dilution — palomino, buckskin, cremello and perlino
• Gray (Presence) — progressive fading that masks the base color

Testing base color? The Base Color Panel covers Red/Black Factor and Agouti together for $40.