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Horse Color Basics
updated
Friday, July 11, 2008
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Genes
All characteristics, including color, are inherited through GENES, which are
located on structures called CHROMOSOMES. They are found in the nucleus of
every cell, and made up of strands of DNA. Genes exist in pairs.
However, the nuclei of egg and sperm cells only have one of each gene from
the individual producing them. So horses, like all mammals, get one of
each gene from the mother, and one of each gene from the father, ending up with
a pair for every possible characteristic.
Red vs. Black (E vs. e)
Horses may have two kinds of pigment in their coats, manes and tails;
RED (e) and/or BLACK (E). Red is called CHESTNUT or SORREL.
These exist as one pair of genes on every horse's chromosome. They
determine what pigment is present in a horse's hair.
GENE WARS? Dominant and recessive genes
So, what if a horse gets a red-hair gene (e) from its father (sire), and a
black-hair gene (E) from its mother (dam)? Will it be a reddish-black
horse if it is Ee?
No, because in horse color BLACK is a DOMINANT gene, which means it will
always show itself, whether there are one or two of them. It will be a
black horse!
But what about that red gene (e)? RED is RECESSIVE in horse color, which
means that it can only show up if there is nothing else at that "spot"
(the red-black spot).
So, the only horses that will be RED are ones that get a red gene from BOTH
parents. Two red genes are needed to make a red horse. (ee)
These two make black-based horses: EE or Ee.
Modifying black: Agouti (Bay, brown, or solid)
We've only discussed one LOCUS (spot where a pair of genes exists) on the
horse's chromosome, so far: the E/e locus. Now we move on to another one,
the AGOUTI locus, which contains a pair of genes that only affect black pigment.
This means that if a horse has only red pigment (is "ee" at the red/black
locus), the genes at the agouti locus have no effect on that horse's color.
If the horse DOES have an "E" gene, meaning it does have black pigment, the
agouti genes affect it as follows:
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A, or the BAY AGOUTI gene, when present on a horse with an E (black
pigment) gene, will limit the black pigment to the points (mane, tail, lower
legs) of the horse.
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At, or the BROWN AGOUTI gene, when present on a horse with an E (black
pigment) gene, will allow the black pigment to spread over most of the body,
but restrict it on the muzzle and underbelly, causing those areas to be a
tan color.
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a, or the BLACK AGOUTI gene, when present on a horse with an E (black
pigment) gene, allows the black pigment to spread through every bit of the
horse's coat. This produces a solid black horse.
Just as black is dominant over red at the red/black locus, bay is dominant
over brown and solid black, and brown is dominant over solid black, at the
agouti locus.
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Chestnut (or "sorrel")
(ee) Red pigment only.
May carry any combination of agouti
genes.
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Bay
(EE or Ee) Black pigment and
(AA, AAt or Aa) bay agouti gene(s).
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Brown
(EE or Ee) Black pigment and
(AtAt or Ata) brown agouti gene(s).
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Black
(EE or Ee) Black pigment and
(aa) two black agouti genes.
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Bay (agouti) is also a dominant gene, so if a horse carries it, it shows up
... and most horses, as we said, do carry the gene.
Enter the Champagne Gene!
The Champagne gene dilutes red to a golden color, and black to a brown or
taupe color.
The Champagne gene is also dominant. So if a horse has even one
Champagne in the pair, it will be a Champagne horse. If CH is Champagne
and ch is non-, then:
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Ch+Ch = Champagne horse
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Ch+ch = Champagne horse
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ch+ ch = non-Champagne horse
Now we get into something that begins to look like algebra, but if you are
calm and take it slowly, you will understand it. J
We are going to look at COMBINATIONS of these three or four genes. The
red/black, the agouti, and the Champagne genes.
EEAAChCh
This horse has two black genes, two bay genes, and two Champagne
genes. So it will have black, but only on the points (bay) and that black
will be diluted to dark brown (Champagne). The body will be made red by
the bay gene, so the Champagne gene will make the body a deep golden
color. This horse will be an Amber Champagne! It may be mistaken for
a buckskin, but it will have brown points, not black, and pinkish skin with
freckles.
EeAaChch
This horse has one each of these dominant genes, so it will be the same as
the one above, because a dominant gene always shows!
Brown + Champagne = sable COMING!
ee(A?)Chch
This horse has no black expressing (ee is red) so we cannot tell whether it
has the bay gene or not (A or a). It does have a Champagne gene, so the red will
be diluted to gold. This horse will be a Gold Champagne. Often
mistaken for Palominos, these horses may or may not have flaxen (white) manes
& tails.
Champagne test now available!
Though none of the ICHR's conclusions have been disproved, there is now a
foolproof way to prove our conclusions. See the link(s) to the test here:
http://www.ichregistry.com/color_test_info.htm
The following horses have been DNA tested and found to be homozygous for the
champagne gene.
This means that they CANNOT HAVE A NON-CHAMPAGNE FOAL.
216, Brooke's Sunny Sue
263, Champagne Shadowfax
342, Jocitas Bit O Honey
407, Dancer's Mystique
499, Skippin the Bars
601, Champagne Cloud Dancer
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