The following is an excerpt from the University of California at Davis's Web page (http://www.vgl.ucdavis.edu/service/horse/coatcolor.html#red_factor):
The basic coat colors of chestnut, bay, brown and black horses are controlled by the interaction between two genes: Extension (gene symbol E) and
Agouti (gene symbol A). The Extension gene (red factor) controls the production of red and black pigment. Agouti controls the distribution of black
pigment either to a points pattern (mane, tail, lower legs, ear rims) or uniformly over the body. The effects of approximately 10 other genes may modify
these pigments to provide an array of colors in the domestic horse ranging from white to black.
The basic colors can be diluted by at least four genes: Cream, Champagne, Dun and Silver. The Cream gene has a dosage effect in that a single copy of
Cream produces palominos, buckskins and smoky blacks. Two doses of Cream produce cremellos, perlinos and smoky creams. Champagne, Dun and
Silver do not show a dosage effect.
There are several genes responsible for white patterns on horses. White spotting patterns on the base coat color are produced by the Dominant White
(one big spot), Appaloosa, Tobiano and Overo genes or as mixed white and colored hair patterns produced by the Grey (progressive whitening with
age) and Roan genes. Several genes may be involved in the production of white spotting patterns known as overo. Among those, the gene responsible
for the frame-overo pattern is associated with a lethal disease of newborn foals called overo lethal white foal syndrome.
Most color assignments can be correctly made based on physical appearance or phenotype alone. However, genetic testing may be necessary to define
phenotypes that are visually ambiguous, such as bays with flaxen manes and tails or chestnuts with dark manes and tails. The same holds true when it is
desirable to know which coat colors can be produced by breeding stock. Researchers at the Veterinary Genetics Laboratory and other institutions are
working towards the identification of the specific genes and mutations responsible for coat color traits in the horse. In the future, diagnostic tests may be
available for all the major coat color genes. Currently, genetic tests are available for: Extension (Red Factor), Agouti, Cream Dilution and Lethal White
Overo.
Red Factor - Extension
The Extension gene (red factor) has two alternative states (alleles). The dominant allele E produces black pigment in the coat. The recessive allele e
produces red pigment. Red horses (chestnuts, sorrels, palominos and red duns, to name a few) are homozygous, that is they have two alleles, for the
recessive red allele ee. Black pigmented horses (black, bay, brown, buckskin and grullo, to name a few) have at least one E allele. They can be
homozygous EE or heterozygous Ee. A horse that is homozygous EE will not produce red offspring, regardless of the color of the mate.
The DNA diagnostic test for red factor can be used to identify those black horses for which neither pedigree nor breeding records is informative for
identifying carriers of the recessive red factor. Since red is inherited as a recessive trait, it is relatively easy to start up a breeding program that will
produce only red horses. It has been more difficult to initiate a black breeding program as black Ee horses can produce red foals. Prior to the
development of this test, only pedigree or breeding records, not phenotype, could provide information about whether black horses are EE or Ee.
The results of the test are reported as:
e: Only the red factor detected. The horse can be assumed to be homozygous for red (ee). The basic color is sorrel or chestnut, but depending on genes
at other color loci, the horse could be palomino, red dun, gray, cremello, white or any of these colors with the white hair patterns tobiano, overo, roan
or appaloosa.
Ee: Both black and red factors detected. The horse can be assumed to be heterozygous for the red factor (Ee). It can transmit either E or e to its
offspring. The basic color of the horse will be black, bay or brown, but depending on genes at other color loci, the horse may be buckskin, zebra dun,
grullo, perlino, gray, white or any of these colors with the white hair patterns tobiano, overo, roan or appaloosa.
E: No red factor detected. The horse can be assumed to be homozygous for black pigment (EE). It cannot have red foals, regardless of the color of the
mate. The basic color of the horse will be black, bay or brown, but depending on genes at other color loci, the horse may be buckskin, zebra dun,
grullo, perlino, gray, white or any of these colors with the white hair patterns tobiano, overo, roan or appaloosa.
Agouti (Bay/Black)
The Agouti gene controls the distribution of black pigment. The dominant allele A restricts black pigment to the points of the horse (mane, tail, lower
legs and ear rims), as seen, for example, in bays and buckskins. The recessive allele a uniformly distributes black pigment over the entire body.
Breeders interested in producing black horses need to have breeding stock carrying the a allele, in addition to the E allele of the Extension gene.
Test results are reported as:
A or Aa: Black pigment distributed in point pattern. The basic color of the horse will be bay or brown in the absence of other modifying genes. A has no
effect on red pigment (ee).
a: Only recessive allele detected. Black pigment distributed uniformly. The basic color of the horse will be black in the absence of other modifying genes.
Cream Dilution Test
The Cream dilution gene is responsible for the palomino, buckskin, smoky black, cremello, perlino and smoky cream coat colors. There are two alleles:
CCr and C. CCr is semi-dominant and dilutes red to yellow in single dose (palominos, buckskins, smoky blacks) and to pale cream in double dose
(cremellos, perlinos, smoky cream). Cream dilution can have a very subtle effect on black pigment. C is recessive and does not dilute the base color.
The results of the test are reported as:
N: Non-dilute. Basic colors are chestnut, bay, black or brown in the absence of other modifying genes.
N/Cr: Heterozygous, dilute, one copy of the Cream CCr allele. Chestnut is diluted to palomino; bay is diluted to buckskin and black is diluted to smoky
black. These colors can be further modified by the actions of other genes.
Cr: Double dilute (two copies of the CCr allele). Chestnut is diluted to cremello; bay is diluted to perlino and black is diluted to smoky cream.
Note: The test offered by VGL is specific for a mutation in exon 2 of the MATP gene that is associated with Cream Dilution. Other dilution genes or
mutations that may produce coat colors that phenotypically resemble cream will not be detected by the test.
The basic coat colors of chestnut, bay, brown and black horses are controlled by the interaction between two genes: Extension (gene symbol E) and
Agouti (gene symbol A). The Extension gene (red factor) controls the production of red and black pigment. Agouti controls the distribution of black
pigment either to a points pattern (mane, tail, lower legs, ear rims) or uniformly over the body. The effects of approximately 10 other genes may modify
these pigments to provide an array of colors in the domestic horse ranging from white to black.
The basic colors can be diluted by at least four genes: Cream, Champagne, Dun and Silver. The Cream gene has a dosage effect in that a single copy of
Cream produces palominos, buckskins and smoky blacks. Two doses of Cream produce cremellos, perlinos and smoky creams. Champagne, Dun and
Silver do not show a dosage effect.
There are several genes responsible for white patterns on horses. White spotting patterns on the base coat color are produced by the Dominant White
(one big spot), Appaloosa, Tobiano and Overo genes or as mixed white and colored hair patterns produced by the Grey (progressive whitening with
age) and Roan genes. Several genes may be involved in the production of white spotting patterns known as overo. Among those, the gene responsible
for the frame-overo pattern is associated with a lethal disease of newborn foals called overo lethal white foal syndrome.
Most color assignments can be correctly made based on physical appearance or phenotype alone. However, genetic testing may be necessary to define
phenotypes that are visually ambiguous, such as bays with flaxen manes and tails or chestnuts with dark manes and tails. The same holds true when it is
desirable to know which coat colors can be produced by breeding stock. Researchers at the Veterinary Genetics Laboratory and other institutions are
working towards the identification of the specific genes and mutations responsible for coat color traits in the horse. In the future, diagnostic tests may be
available for all the major coat color genes. Currently, genetic tests are available for: Extension (Red Factor), Agouti, Cream Dilution and Lethal White
Overo.
Red Factor - Extension
The Extension gene (red factor) has two alternative states (alleles). The dominant allele E produces black pigment in the coat. The recessive allele e
produces red pigment. Red horses (chestnuts, sorrels, palominos and red duns, to name a few) are homozygous, that is they have two alleles, for the
recessive red allele ee. Black pigmented horses (black, bay, brown, buckskin and grullo, to name a few) have at least one E allele. They can be
homozygous EE or heterozygous Ee. A horse that is homozygous EE will not produce red offspring, regardless of the color of the mate.
The DNA diagnostic test for red factor can be used to identify those black horses for which neither pedigree nor breeding records is informative for
identifying carriers of the recessive red factor. Since red is inherited as a recessive trait, it is relatively easy to start up a breeding program that will
produce only red horses. It has been more difficult to initiate a black breeding program as black Ee horses can produce red foals. Prior to the
development of this test, only pedigree or breeding records, not phenotype, could provide information about whether black horses are EE or Ee.
The results of the test are reported as:
e: Only the red factor detected. The horse can be assumed to be homozygous for red (ee). The basic color is sorrel or chestnut, but depending on genes
at other color loci, the horse could be palomino, red dun, gray, cremello, white or any of these colors with the white hair patterns tobiano, overo, roan
or appaloosa.
Ee: Both black and red factors detected. The horse can be assumed to be heterozygous for the red factor (Ee). It can transmit either E or e to its
offspring. The basic color of the horse will be black, bay or brown, but depending on genes at other color loci, the horse may be buckskin, zebra dun,
grullo, perlino, gray, white or any of these colors with the white hair patterns tobiano, overo, roan or appaloosa.
E: No red factor detected. The horse can be assumed to be homozygous for black pigment (EE). It cannot have red foals, regardless of the color of the
mate. The basic color of the horse will be black, bay or brown, but depending on genes at other color loci, the horse may be buckskin, zebra dun,
grullo, perlino, gray, white or any of these colors with the white hair patterns tobiano, overo, roan or appaloosa.
Agouti (Bay/Black)
The Agouti gene controls the distribution of black pigment. The dominant allele A restricts black pigment to the points of the horse (mane, tail, lower
legs and ear rims), as seen, for example, in bays and buckskins. The recessive allele a uniformly distributes black pigment over the entire body.
Breeders interested in producing black horses need to have breeding stock carrying the a allele, in addition to the E allele of the Extension gene.
Test results are reported as:
A or Aa: Black pigment distributed in point pattern. The basic color of the horse will be bay or brown in the absence of other modifying genes. A has no
effect on red pigment (ee).
a: Only recessive allele detected. Black pigment distributed uniformly. The basic color of the horse will be black in the absence of other modifying genes.
Cream Dilution Test
The Cream dilution gene is responsible for the palomino, buckskin, smoky black, cremello, perlino and smoky cream coat colors. There are two alleles:
CCr and C. CCr is semi-dominant and dilutes red to yellow in single dose (palominos, buckskins, smoky blacks) and to pale cream in double dose
(cremellos, perlinos, smoky cream). Cream dilution can have a very subtle effect on black pigment. C is recessive and does not dilute the base color.
The results of the test are reported as:
N: Non-dilute. Basic colors are chestnut, bay, black or brown in the absence of other modifying genes.
N/Cr: Heterozygous, dilute, one copy of the Cream CCr allele. Chestnut is diluted to palomino; bay is diluted to buckskin and black is diluted to smoky
black. These colors can be further modified by the actions of other genes.
Cr: Double dilute (two copies of the CCr allele). Chestnut is diluted to cremello; bay is diluted to perlino and black is diluted to smoky cream.
Note: The test offered by VGL is specific for a mutation in exon 2 of the MATP gene that is associated with Cream Dilution. Other dilution genes or
mutations that may produce coat colors that phenotypically resemble cream will not be detected by the test.
| IF THE CHART OVERLAPS WITH TEXT, HIT THE REFRESH BUTTON. What color will my foal be??? If you breed your mares to our stallions, the following chart contains the percent chance that the foal produced will be a certain color. Select a stallion on the chart you wish to breed to and look for your mare's color. If there is not a color listed as a percentage, there is no chance of that color foal being produced from that particular cross. Hes Dun Time in Gold has not yet been tested by the University of California at Davis for his coat genotype. His column will be update when testing is competed. His genotype is being treated as heterozygous for the Agouti though he may be homozygous recessive or dominant. Below farther is more information on how coat color genetics works. |
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