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Encyclopedia > Equine coat color genetics

There are currently two theories of equine coat color genetics: Dr. Ann Bowling's and Dr. Phillip Sponenberg's. These theories overlap, and have more similarities than differences. This article is a combination of the two gene theories, presented in Dr. Bowling’s format.

Contents

Background

A basic understanding of heredity is helpful for this subject. For a quick lesson in genetics and heredity, see the article on alleles or this tutorial on inheritance. Heredity (the adjective is hereditary) is the transfer of characteristics from parent to offspring, either through their genes or through the social institution called inheritance (for example, a title of nobility is passed from individual to individual according to relevant customs and/or laws). ... For a non-technical introduction to the topic, please see Introduction to genetics. ... An allele is any one of a number of alternative forms of the same gene occupying a given locus (position) on a chromosome. ...


Regarding references to melanin (pigment or coloring): There are two chemically distinct types of melanin, the red–yellow phaeomelanin and the brown–black eumelanin. All coloration genes in mammals affect either the production or final effect of these two chemicals. Broadly, melanin is any of the polyacetylene, polyaniline, and polypyrrole blacks and browns or their mixed copolymers. ...


The terms Alleles and Modifiers are used interchangeably in this article.


Socks, Star, Strip, and Snip genetics are not yet fully understood but are probably influenced by multiple alleles.


Alleles and effects

Alleles Effect of combined pairs of alleles
W W
w		 WW: Lethal. Results in incomplete colon and the inability to defecate. Probably from a gene near W or O but not influencing the color directly.)
Ww: Horse typically lacks pigment in skin, hair and eyes and appears to be white.
ww: Horse is fully pigmented.
G G
g		 GG or Gg: Horse shows progressive silvering with age to white or flea-bitten, but is born a non-gray color. Pigment is always present in skin and eyes at all stages of silvering. Gray horses range from white to dark gray depending on the proportion of white hairs in the coat, horses' coats gray in a manner similar to graying in human hair.
gg: Horse does not gray with aging.
E E
e		 EE or Ee: Horse forms black pigment in skin and hair. Black pigment in hair may be either in a points pattern or uniformly distributed.
ee: Horse has black pigment in skin, but red pigment in hair.

Horse will not appear red if white, gray, roaning, or dilution genes are present. Colon has several meanings: colon (anatomy) colon (punctuation) colon (rhetoric) See also Colón This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... A truly white horse has pink skin under their white hair coat True white horses, especially those that carry the White or W gene, are extremely rare. ... Gray is a coat color of horses, consisting of black skin, a white to dark gray coat, and a mane the same color or darker than the body coat. ... Friesian horses are one of the best-known breeds of black-colored horse Black is a relatively uncommon coat color in horses, though not so unusual as to be considered rare. ...

E+ also noted as Ed. E+
e+		 Contrary to popular belief, this does not actually occur on the same locus as the E and e alleles.

E+E+or E+e+: Dominant black, non-fading – Overrides the A or bay allele resulting in an all black horse.
e+e+: no effect. Unproven theory.[citation needed] Friesian horses are one of the best-known breeds of black-colored horse Black is a relatively uncommon coat color in horses, though not so unusual as to be considered rare. ...

A A
a		 Agouti-Bay: Acts on "E" to restrict eumelanin, or black pigment, to points, allowing red coat color to show on body. Has no effect on "e" or red.
AA or Aa horse has black hair (E not E+), then that black hair shows only in points pattern (usually mane, tail, legs, sometimes tips of ears).
aa: If horse has E allele, then horse will be uniformly black.
C C
c		 Dilution factor cream gene: Acts three possible ways

1) cc: No dilution factor, horse is fully pigmented.
2) Cc: Single dilution factor, results in Palomino, Buckskin or Smoky Black. Red pigment is diluted to gold with cream to white mane and tail; black pigment is not visibly altered on buckskin or black horses, though genetic testing can reveal "smoky black" coloration. Bay is a color of the hair coats of horses, characterized by a body color of dark red (known as blood bay) to deep brown, with black points (mane, tail, lower legs, and sometimes the muzzle and tip of the ears). ... Melanin is a polymer of either or both of two monomer molecules: indolequinone, and dihydroxyindole carboxylic acid. ... The cream gene is a dilution gene expressed in horses, and produces lighter colors. ... The genetics of cat coat length and coloration is a complex subject, and many different genes are involved. ... Palomino is a coat color in horses, consisting of a gold coat and white or flaxen mane and tail. ... Buckskin is a color of horses; it also refers to other things that are the color of a buckskin horse, such as the color of some breeds of dogs. ...

3) CC Cremello or Perlino: Double dilution factor. Red pigment is diluted to a pale cream (cremello). Black pigment is diluted to a reddish shade. Skin and eye color are also diluted, and blue eyes are common with double diluted creams.
D D
d		 DD or Dd: Dun horse shows a diluted body color to pinkish-red, yellow-red, yellow or mouse gray and has dark points including dorsal stripe, shoulder stripe and leg barring.
dd: Horse has undiluted coat color.
TO TO
to		 TOTO or Toto: Produces regular and distinct ovals or round patterns of white and color that extend down over the neck and chest, giving the appearance of a shield.
toto: No tobiano pattern present.
O Also noted as Fr or FrO O
o		 OO or Oo: Overo or Frame Overo pattern - Color forms a frame around white patterning. Overo as an allele is different from overo as a registration since the registration also includes the splash and sabino alleles. Homozygous associated with lethal white syndrome.
oo: No overo pattern present.
Ch Ch
ch		 Champagne: A rare dilution gene that creates pumpkin-colored freckled skin, amber or blue eyes, and gives a bronze cast to hair. The skin surrounding the eye must be pink with freckles. A champagne horse is born with a darker foal coat that lightens with maturity.
ChCh or Chch: Champagne dilution evident (See Genetic Formulas Chart below.)
chch: No champagne dilution
F F
f		 Effects visible on red or chestnut colors only.
FF or Ff: Red points on ee horses.
ff: Flaxen points on ee horses. Unproven theory.[citation needed]
P P
p		 Pangare (Mealy): The effects of this allele appear along the underside of the horse, in the "soft" parts, or on the muzzle, behind the elbows, in the flanks, on the buttock, above or around the eyes, and along the belly.
PP or Pp: Mealy or Pangare dilution of pigment.
pp: no mealy looking lightening of pigment.
Rn Rn
rn		 RnRn or Rnrn: roan pattern of white hair mixed in with base color. There is no lethal roan question.
rnrn: No roan pattern.
Rb Rb
rb		 Rabicano: Partial roaning with ‘coon’ tail markings. Thought to be a dominant gene by Sponenberg.
RbRb or Rbrb: Rabicano markings.
rbrb: No rabicano traits.
Sb Sb
sb		 Sabino - Feathery white markings like those of Misty of Chincoteague.
Only paint marking pattern found in full blooded Arabians. Sabino may well be polygenic (a gene-complex rather than a single gene pair) and causes abundant white on the legs, and then creeps up as belly spots and body spots that are can be flecked and roaned. Sabino is registered as overo by some registries, but does not entail the overo or frame overo allele. No risk of lethal white.
SbSb or Sbsb: Sabino markings.
sbsb: No sabino marks.
Spl Spl
spl		 Splash, Splashed White - Looks like reverse tobiano with white moving from the bottom of the horse towards the top. The horse's head will look as if dunked in bucket of white paint. White coloring appears to move boldly and smoothly from bottom up. Commonly has blue eyes.
SplSpl or Splspl: Splashed markings. Splash is registered as overo but does not entail the overo or frame overo allele and is not associated with lethal white syndrome.
splspl: No splashed markings.

Alternate theory: Incomplete dominant. SplSpl:classic Splash markings.Splspl:socks, face markings, may be small in the "normal" marking range or into the pinto range with or without blue eyes. splspl causes no white at all. Cremello is a color of horse consisting of a cream-colored body with a cream mane and tail. ... Perlino is a color in horses created by a dilution gene, also known as the creme gene acting on an underlying Bay coat color. ... The cream gene is a dilution gene expressed in horses, and produces lighter colors. ... Dun is a yellow-brown color, sometimes seen in the hair coats of horses, characterized by a body color ranging from sandy yellow to reddish-brown. ... Tobiano is a genetic trait among horses which produces a characteristic white pattern in the coat. ... Overo is the name of a coloration pattern in American Paint Horses in which the horses head is bald or nealy bald. ... This Clydesdale horse has classic Sabino belly spots, white above its hocks, a chin spot and wide white facial markings. ... Lethal white syndrome (LWS) is a common genetic disorder primarily associated with American Paint Horses. ... The color champagne is a name given for several pale shades of yellow or beige. ... A red roan horse Roan is a type of coat color in horses (and, occasionally, in other animals, such as dogs and cattle) that is a mixture of white hairs with a base coat of another color. ... There are currently two theories of equine coat color genetics: Dr. Ann Bowlings and Dr. Phillip Sponenbergs. ... Rabicano is a horse coat color that appears to be a type of partial roaning. ... This Clydesdale horse has classic Sabino belly spots, white above its hocks, a chin spot and wide white facial markings. ... Misty of Chicoteague was a book written by Marguerite Henry in 1947 Marguerite Henry (April 13, 1902-November 26, 1997) was the an American writer. ... This Clydesdale horse has classic Sabino belly spots, white above its hocks, a chin spot and wide white facial markings. ...

Sty Sty

sty

 Sooty
StySty or Stysty: Black mixed into body coat.
stysty: No black mixed into coat.
Z Z

z

 ZZ or Zz: Silver dapple - Dilutes eumelanin or black pigment. Converts black to brown with white mane and tail or results in silver coloring.
zz: No silver dapple.
Lp Lp
lp		 Appaloosa spotting gene. The effects of this allele are minimallized or suppressed in horses carrying E or E+[citation needed]

This article needs to be cleaned up to conform to a higher standard of quality. ... The Appaloosa is a horse breed, in which the horse has one of several distinct patterns of spots. ...

Genetic formulas and color definitions

Partial list of Genetic Formulas and Color Definitions
Chart based on Dr. Bowling’s Genetic Formulas
W White
G Gray
E, A, CC, dd, gg, ww, toto Bay or Brown
E, aa, CC, dd, gg, ww, toto Black
ee, aa, CC, dd, gg, ww, toto Red: Sorrel or Chestnut
E, A, CCcr, dd, gg, ww, toto Buckskin
ee, CCcr, dd, gg, ww, toto Palomino
ee, CcrCcr Cremello
E, CcrCcr Perlino
E, A, CC, D, gg, ww, toto Yellow or "buckskin" Dun
E, aa, CC, D, gg, ww, toto Mouse Dun, Blue Dun or Grulla
E,A,CC,D Dun, Zebra Dun, Bay Dun, Classic Dun
ee, CC, D, gg, ww, toto Red Dun
gg, E, aa, CC, dd, RN Black Roan (Blue Roan)
gg, E, A, CC, dd, RN Bay Roan
gg, ee, CC, dd, RN Red Roan
gg, E, A, CCcr, dd, RN Buckskin Roan (Red Roan) 
gg, ee, CCcr, dd, RN Palomino Roan (Red Roan)
gg, E, A, CC, D, RN Buckskin Roan (Red Roan)
gg, E, aa, CC, D, RN Mouse Dun Roan, Grulla Roan, or Blue Roan&
gg,ee, CC, D, RN  Red Dun Roan (Red Roan)
gg, E, A, CC, dd, gg, ww, TO Bay Tobiano
gg, ee, CC, D, gg, ww, TO Red Dun Tobiano
gg, Ch, ee, aa, CC, dd, gg, ww, toto Gold - looks like Palomino
gg, Ch, E, A, CC, dd, gg, ww, toto Amber
gg, Ch, E, aa, CC, dd, gg, ww, toto Champagne
gg, Ch, ee, CcrCcr &Ivory&
gg, E, aa, CC, dd, TO, Sb Black Sabino-Tobiano (Tovero without lethal white.)
gg, E, aa, CC, dd, TO, O Black Tobiano-Overo (Tovero carrying lethal white.) 
ee, CCcr, dd, gg, ww, TO Palomino Tobiano Paint
gg, ee, aa, CC, dd, TO, Spl Red Tobiano-Splash (Tovero without lethal white.)

Bay is a color of the hair coats of horses, characterized by a body color of dark red (known as blood bay) to deep brown, with black points (mane, tail, lower legs, and sometimes the muzzle and tip of the ears). ... Friesian horses are one of the best-known breeds of black-colored horse Black is a relatively uncommon coat color in horses, though not so unusual as to be considered rare. ... Chestnuts. ... Buckskin is a color of horses; it also refers to other things that are the color of a buckskin horse, such as the color of some breeds of dogs. ... Palomino is a coat color in horses, consisting of a gold coat and white or flaxen mane and tail. ... Cremello is a color of horse consisting of a cream-colored body with a cream mane and tail. ... Perlino is a color in horses created by a dilution gene, also known as the creme gene acting on an underlying Bay coat color. ... Dun is a yellow-brown color, sometimes seen in the hair coats of horses, characterized by a body color ranging from sandy yellow to reddish-brown. ... Grullo is a color of horses, characterized by smoky or mouse colored hairs on the body, often with shoulder and dorsal stripes and black barring on the lower legs. ... Dun is a yellow-brown color, sometimes seen in the hair coats of horses, characterized by a body color ranging from sandy yellow to reddish-brown. ... Dun is a yellow-brown color, sometimes seen in the hair coats of horses, characterized by a body color ranging from sandy yellow to reddish-brown. ... A red roan horse Roan is a type of coat color in horses (and, occasionally, in other animals, such as dogs and cattle) that is a mixture of white hairs with a base coat of another color. ... A red roan horse Roan is a type of coat color in horses (and, occasionally, in other animals, such as dogs and cattle) that is a mixture of white hairs with a base coat of another color. ... A red roan horse Roan is a type of coat color in horses (and, occasionally, in other animals, such as dogs and cattle) that is a mixture of white hairs with a base coat of another color. ... Tobiano is a genetic trait among horses which produces a characteristic white pattern in the coat. ... Tobiano is a genetic trait among horses which produces a characteristic white pattern in the coat. ... The Tovero coloration is a mix of tobiano and overo colorations in Pinto horses and American Paint Horses. ... The Tovero coloration is a mix of tobiano and overo colorations in Pinto horses and American Paint Horses. ...

Lethal roan question

Hintz, H. F. and VanVleck, L. D., published 1979. "Lethal Dominant Roan in Horses". Journal of Heredity, 70:145-146. This study, based on percentages of roan foals thrown by roan parents, popularized the idea of Lethal Roan Syndrome. The study did not include direct genetic analysis and assumed fetus absorption preventing birth. Similar studies suggested that roan-to-roan breedings were lethal because the resulting embryos were absorbed. This was thought to be true because homozygous roans, horses that carried two alleles for the roan characteristic, were rare.


A recent genetic study of roans by Dr. Bowling [1] refuted Hintz and VanVleck’s inferences. Using genetic analysis, Dr. Bowling found several homozygous roans and no evidence of a Lethal Roan Syndrome.[citation needed]


Sources and external links


  Results from FactBites:
 
Coat Color Genetics (3980 words)
A scheme of coat color classification based on recognition of the effects of the alleles of seven genes provides the necessary rigor, and with training can be uniformly applied by anyone to define most of the common colors encountered in horses.
For homozygous recessive colors, both alleles are written in the notation for color assignment, since a horse showing a color or pattern produced by recessives is by definition homozygous for the recessive alleles.
Adelsteinsson Stefan: Inheritance of the Palomino Color in Icelandic Horses.
Equine coat color genetics - definition of Equine coat color genetics in Encyclopedia (595 words)
The color of a horse is based on two base colors: red (chestnut in color) and fl.
The Agouti Gene (A): bay coloration, which is always on a fl base.
The flaxen gene lightens the mane and tail of horses
  More results at FactBites »


 
 

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