Phaetomelanin, which is RED, and recessive.  


Eumelanin, which is BLACK
(or brown, depending upon environmental or genetic modifications) and is Dominant

Chemically, all horse colors are made up of two chemicals:  Phaeomelanin or Eumelanin.

Genetic modifiers work on these two pigments (eumelanin and phaeomelanin) to create all the variety of colors and patterns that we see in horses.
See HOW GENES WORK

WHAT ABOUT WHITE? 

There MAY be a third base color - Dominant White, but this is very rare if it exists at all. Recent research throws the existence of a separate White gene in doubt, although many textbooks still include it.

Most White is the result of genetic modification that blocks or removes the base color.

Most White horses are, genetically:

  • Maximum Sabino or Tovero
  • The end result of Greying
  • One-spot Appaloosas (where the "spot" is small and not obvious)
  • or very pale Cremellos
     

    Gretchen, a dark-eyed, pink-skinned white mustang adopted by Gwilda Byrd. Dominant White? Maximum Sabino? Few Spot Appaloosa? No one knows for sure. With dark eyes, she is not a cremello.

What About ALBINOS?

In horses, no true Albino (an individual lacking any pigmentation) has ever been found. If you stand a so-called Albino horse next to a pinto, you will see the difference. The "Albino" is usually the pale cream of Cremello, whereas the white on a pinto is pure white.

Maximum Sabinos or Maximum Toveros are true white and can have blue eyes and mostly light skin, but they are not albinos. Usually there will be at least one small dark spot in the skin or at the tip of the ears. And their eyes are blue or brown, not red or pink.

Dominant White horses are also pure white, but they, too, are not albinos.

A true albino would have no pigmentation at all - uniform light pink skin, white hooves, red/pink eyes.


Left: "White" horse at a BLM adoption - probably a Maximum Sabino
Right: Cremello mustang (blue eyes reflecting the camera's flash)

Science: HOW BASE COLORS ARE DETERMINED

The Base Color is determined at the "Extension" locus (locus means, literally, "place") on the DNA strand. The dominant form of the Extension locus, "E"  allows both black and red, although in reality (unless other genetic factors, such as Agouti are present) a horse with "E" will have a black base color, since black is dominant. The recessive extension "e" allows only red.

Is BAY a BASE COLOR?

Many people speak of BAY as a base color.

Bay can be considered a base color in that it is the foundation for a variety of other colors, such as buckskin and dun and red roan.

But since Bay is Black modified by an additional gene - Agouti - it is not a "BASE COLOR" from a genetic point of view.
 

photo by Joy Hartman

Other Pages In the Color Section of this Website:

Major Headings:

The Base Colors:

The Single Dominant Genes:
Agouti | Appaloosa |
Brindle | Dun | Grey | Pangare | Pintos Rabicano | Roans & Roaning | Silver | Sooty |

The Pinto / Paint Patterns:
Tobiano | The Overo Complex: Frame | Sabino | Splash | Tovero

The Incomplete Dominant Genes:
Champagne | Creme

The Recessive Genes:
Red | Flaxen

Colors with multiple genetic bases:
Blue | Brown | White | Roan-like Effects

Other pages in this section:

A Quick Overview of Color GeneticsGenetic Notation SystemsHow to Tell the Various Pinto Patterns Apart
Palomino or Flaxen Chestnut? Overo Lethal White SyndromeSorraia Mustangs

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Color genetics are the same for all horses, regardless of breed or ancestry.

Since this is a Mustang website,
I use and prefer pictures of wild, or formerly-wild horses wherever possible.