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Genetics 000
Dark Colors

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The pigment colors --- black and red,
and the agouti genes ---
bay, brown and solid (black),
combine to produce four dark, "pure" (undiluted) colors:

These are the dark foundations
upon which all other horse colors are built.

Other genes, like white markings, the various dilutions, graying, roan and the leopard complex (appaloosa), work by simply changing the expression of these four pure, dark colors.

Characteristics of the four dark base colors resulting from the interaction of pigment and agouti, without any other known color modifiers:

1. Chestnut  (Red)  =  ee   plus any agouti A, At or a

Body color any shade of red, reddish-brown, or orangey-red; points may be lighter or darker than the body, or the same color, but not true black. May be called sorrel.  Chestnut shades range from "blond" chestnut, which looks palomino, to "sooty"*, or "liver" chestnut, which can appear almost black.

2. Bay   =  EE or Ee   plus  AA,  Aa, or AAt

Body color red or reddish-brown, ranging from light to dark; points black. Sooty* bays may have an overlay of black hairs on the body, but the color underneath will still be red.

3. Brown (aka Seal Brown) = 
                               EE or Ee  plus  AtAt  or  Ata

There is now a DNA test to differentiate this color combination from bay or black.  The typical brown is a black horse with tan highlights  in specific areas -- the muzzle, flanks, underbelly, and girth areas.  Shades of (seal) brown can range from almost all black to more like a "sooty* tan" horse.

4. Solid Black   =   EE or Ee    plus   aa

The horse is black all over, including the muzzle, flanks and underbelly. Blacks may fade when exposed to the sun, but the new coat comes in true black, after each shedding.  Black seems to also come in "shades": from a nearly blue-black that never fades, to "fading black", which comes in true black but lightens to red when exposed to the elements, to "light black" **, which always has a brownish cast to it, and can even look tan on large areas of the body.

**A word about "light black", which has only been tentatively identified in a few equine families.  This does not refer to the variation in black caused by the leopard complex (Appaloosa) genes, or by fading.  A true "light black" horse tests as a solid black, with no other known dilutions or color modifiers, yet has no truly black hair anywhere on its body; even when the new coats come in, the hair is all various shades of brown or tan.  It remains to be seen what causes this, genetically.

* Sooty, sootiness, smutty, smuttiness, shaded, shading: not yet understood genetically, "sooty" "smutty" or "shaded" are all descriptive terms for a horse's "red" areas being covered, to varying degrees, with darker, or even black-looking hairs.



E and e are the pigment genes

E = black pigment present, and is dominant over e

e = red pigment only, but is only expressed if the horse is ee


A, At, and a are the agouti genes,
                              only affecting black pigment (E)

A = bay, and is dominant over the other two agouti genes

At = brown, and is recessive to bay
                                but dominant over solid black

a = solid black, and is recessive to the other two agouti  
                   genes, and so only expressed if the horse is aa

  •  The next genes this site will explore are the DILUTION genes. 
      Click Dilutions to learn about Cream, Dun, Silver,
      Champagne, and Pearl

...or, you may want to skip to another set of color modifying genes
of particular interest to you. 

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Chestnut Bay Brown Black Breeding Darks

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