|
Color Genetic Info
Red/Black Gene
All horses, whether it be black, chestnut, gray, bay, white, dun, roan, etc.
have their coat color built on one of two possible base pigments;
red or black.
No matter what color your animal is, the "base"
color must be either red or black!
The production of this "base" color is controlled by the Extension gene.
In other words, the Extension gene controls the production of
red or black pigment. The red producing gene (e) or Red Factor is recessive
and the black producing gene (E) or black factor is dominant.
Thus, a horse carrying at least one copy of the black gene (E/e or E/E)
will have black base in its coat. Only horses testing homozygous
for red factor (e/e) will have a red base coat.
The final color, shade and/or pattern of a horses coat will be
determined by many other possible color genes and gene mutations
that act upon the "base" coat of the horse.
For example, a palomino is a red (chestnut or sorrel) horse
that has been diluted by the Cream Dilution gene.
A Red Roan is a red (chestnut or sorrel) horse with the "roan" gene,
and so on and so forth.
Along with red and black, the color bay is also often referred to
as a base coat color. Bays are actually just another black based horse.
But in this case the black base has been modified by the Agouti
gene by restricting the black pigment to the
points (mane, tail, etc.) of the horse.
Often, breeders of black horses will want to test for Red Factor
to determine if the horse is homozygous for black (EE) or
heterozygous for black (E/e).
Homozygous black horses will always throw black as a
base coat and will never produce red based offspring.
Other reasons to test for Red Factor would be to
verify that a horse has a chestnut or sorrel (ee) base.
For instance, Cremellos, Palominos, Red Roans,
and Red Duns are red based
horses and would test homozygous for Red Factor (ee).
(e/e)
Only the red factor detected. The horse tested homozygous for
red pigment. The basic color is chestnut or sorrel unless
modified by other color modifying genes.
(E/e)
Both black and red factors detected. The horse tested heterozygous
for the red factor. It can give either (E) or (e) to its offspring. The
basic color of the horse will be black, bay or brown unless
modified by other color modifying genes.
(E/E)
Only the black factor detected. The horse tested homozygous for
black pigment. It cannot have red foals regardless of the color of
the mate. The basic color of the horse will be black, bay or
brown unless modified by other color modifying genes.
Agouti Gene
The Agouti gene controls the distribution of black pigment. The black
pigment can be either uniformly distributed as with a black horse,
a grullo or a blue roan for example or distributed to the "points"
of the horse (ear rims, lower legs, mane, tail) as seen with bays,
buckskins, buckskin duns, or bay duns.
Only when the agouti gene is homozygous for the deletion (a/a) is the black
pigment evenly distributed resulting in a black animal.
Heterozygous (Aa) or homozygous (AA) results in point distribution of
black pigment which can only be seen on "black" based animals
(E/e or E/E). Agouti has no effect on homozygous positive red
factor (e/e) horses for there has to be black pigment
present for agouti to have an effect.
Since agouti is not shown physically on red (e/e) horses, a breeder might
want to test a red based horse (chestnuts, sorrels, palominos, & cremellos)
to see if it is an Agouti carrier. Testing bay horses might be desired
to see whether the horse carries one (A/a) or two (A/A) copies of the
Agouti allele. A homozygous Agouti (A/A) horse will always pass
Agouti to its offspring whereas a heterozygous (Aa) horse
will have a 50% chance of passing on the gene.
Another reason to test for Agouti might be if there is some doubt
whether a black horse is truly black or a very dark bay. The effects
of other genes might also make it hard to tell if Agouti is present or not.
(a/a)
Only recessive allele detected. Black pigment distributed uniformly.
The basic color of the horse will be black in the absence
of other color modifying genes.
(A/a)
Horse tested Heterozygous for Agouti. Black pigment distributed in point pattern.
The horse can transmit either A or a to its offspring. The basic color of the horse
will be bay or brown unless modified by other color modifying genes.
(A/A)
Only dominant allele detected. Black pigment distributed in point pattern.
The horse cannot have solid black foals regardless of the color of the mate.
The basic color of the horse will be bay or brown in the absence
of other color modifying genes.
Creme Dilution
The cream dilution gene controls the amount of base color dilution
of a horse's coat. This gene has a dosage effect where a heterozygous cream
dilution horse will have a lesser effect when compared to a homozygous cream dilution horse.
Heterozygous cream dilution producing buckskins, smoky blacks,
and palominos and homozygous cream dilution producing cremellos,
perlinos, and smoky creams.
| No Dilution |
Single Dilute |
Double Dilute |
| Sorrel |
Palomino |
Cremello |
| Black |
Smoky Black |
Smoky Creme |
| Bay |
Buckskin |
Perlino |
|