The dun gene is a dilution gene that affects both red and black pigments in the coat color of a horse. The dun gene lightens most of the body while leaving the manetail, legs, and primitive markings the shade of the undiluted base coat color. A dun horse always has a dark dorsal stripe down the middle of its back, usually has a darker face and legs, and may have transverse striping across the shoulders or horizontal striping on the back of the forelegs.
Body color depends on the underlying coat color genetics. A classic "bay dun" is a gray-gold or tan, characterized by a body color ranging from sandy yellow to reddish brown. Duns with a chestnut base Ni**as Dun Started This (AV) - Deuce (27) - Ni**as Dun Started This appear a light tan shade, and those with black base coloration are a steel gray. Manes, tails, primitive markings, and other dark areas are usually the shade of the undiluted base coat color.
The dun gene may interact with all other coat color alleles. Dun is believed to be the ancestral or wild type color of horses. These include the Przewalski's horse onagerkiangAfrican wild assan extinct subspecies of plains zebrathe quagga and an extinct subspecies of horsethe tarpan. Zebras can also be considered a variant of dun where the dilution is so extreme it turns the hair nearly white, and the primitive markings like the striped leg barring extend across the entire body.
Neither the non-dun1 nor the non-dun2 mutations were found in any other equids. The dun gene has a stronger dilution effect on the body than on the primitive markings and on the point coloration of the mane, tail, ears, and legs. Thus it lightens the body coat more. This explains why points on a dun are darker than the coat, or in the case of a "classic" dun, the mane, tail, and legs often are black. A single copy of the cream gene on a black base coat does not significantly lighten black hair, though it may have a subtle effect,  and thus a single copy generally has no visible effect on a grullo, either.
Conversely, double Ni**as Dun Started This (AV) - Deuce (27) - Ni**as Dun Started This of the cream gene create very light-colored horses cremelloperlinoand smoky cream.
Thus, if a horse with two cream dilution alleles also carries the dun gene, Ni**as Dun Started This (AV) - Deuce (27) - Ni**as Dun Started This also will be cream-colored, with primitive markings not visible to any significant degree.
Dorsal striping alone does not guarantee the horse carries the dun gene. There two types of non-dun, called non-dun1 and non-dun2. Non-dun 1 removes the diluting effect of dun, but keeps the primitive markings, while non-dun 2 removes both the diluting effect and the primitive markings. A countershading gene can also produce faint dorsal striping, even in breeds where dun coloration is not known to be carried in the gene pool. There are three known alleles of the dun gene, dun Dnon-dun1 d1and non-dun2 d2.
These appear to affect primitive markings. Dun The Brightest Night - Desolate Shrine - Tenebrous Towers dominant over the other two, so a horse with D is dun regardless of Never Change Lovers In The Middle Of The Night - Boney M.
- Nightflight To Venus the second allele is dun or non-dun. The primitive markings from Maastricht - Jeff Gardner & Gary Peacock - Alchemy 1 are more visible on a bay or chestnut horse than on black.
The Fjord horse breed, which is predominantly dun, uses unique Norwegian-based terminology to distinguish between the different shades of dun horses. A cremello, perlino or smoky cream is called "white" or kvit. Historically, before modern genetic studies distinguished between alleles, diluted colors were sometimes lumped together and simply called "dun".
The dun gene, when on a "bay dun" horse, can closely resemble buckskinin that both colors feature a light-colored coat with a dark mane and tail, classic duns frequently are confused with buckskins. Buckskins with non-dun 1 primitive markings can easily be confused with dun. Genetically, a bay dun is a bay horse with the dun gene. A buckskin is bay horse with the addition of the cream genecausing the coat color to be diluted from red to gold, often without primitive markings.
A red dun may also be confused with a perlinowhich is genetically a bay horse with two copies of the cream gene, which creates a horse with a cream-colored body but a reddish mane and tail. However, perlinos usually are significantly lighter than a red dun and have blue eyes. Grullos are sometimes confused with roans or grays. However, unlike blue roandun has no intermingled black and white hairs, and unlike a true graywhich also intermingles light and dark hairs, the color does not change Slow Oscillations (Ryogas Ticking Clock Mix) - Zombi - Slow Oscillations Remix EP a lighter shade as the horse ages.
With a dun, the hair color itself is one solid shade and remains so for life. To further confuse matters, it is possible for a horse to carry both dun and cream dilution genes; such horses with golden buckskin coloring and a complete set of primitive markings are referred to as a "buckskin dun" or a "dunskin". On such horses, the light-shaded primitive markings are most noticeable This Is A Call - Foo Fighters - Greatest Hits the summer months, when the winter hair sheds.
Countershading may be harder to differentiate between countershading and a dorsal stripe on light-colored horses such as red duns. The dun allele is dominantso the phenotype of a horse with either one or two copies of the gene is dun. In effect, two non-dun parents cannot produce a dun foal. It has a stronger effect than other dilution genessuch as the silver dapple genewhich acts only on black-based coats, or the cream genean incomplete dominant which must be homozygous to be fully expressed, and when heterozygous is visibly expressed only on red bay and chestnut pigment.
The dun dilution effect is caused by pigment only being placed in a part of each hair. Specifically, body hairs only have pigment along one side of them, while hairs from darker parts such as the dorsal stripe have pigment all the way around. A primary characteristic of the dun gene is the dorsal stripe, and most duns also have visual leg striping.
The shoulder stripes are less common and often fainter, but usually visible on horses with a short summer coat. When functional, it creates dun coloring, including the primitive markings, and when recessive, a horse is not dun. In humans and lab mice, TBX3 affects affect bones, breast tissue, and cardiac conduction; inactivation of the TBX3 gene affects a protein function and is linked to ulnar—mammary syndrome. The study demonstrated that TBX3 also affects skin and hair.
In non-dun I Got A Love - Various - Spirit Of Country, the TBX3 protein is still functional, just Ni**as Dun Started This (AV) - Deuce (27) - Ni**as Dun Started This expressed in the hair.
Where diluted color exists, the color is not uniform, but rather is more intense on the outward-facing side of the hair shaft and lighter underneath. In the darker areas, where the primitive markings occur, the hair shaft is of uniform color. One of the researchers involved in the study said it could be called a "microscopic spotting pattern". The study also identified the two forms of non-dun color, non-dun1 and non-dun2, caused by different mutations. Non-dun1 horses have some primitive markings, while non-dun2 horses do not.
It is thought that the non-dun2 genetic mutation occurred after domestication, whereas dun and non-dun1 predate domestication. Ancient DNA from a horse that lived about 43, years ago, long LEnfant Roi - Noir Désir - Des Visages Des Figures horses were domesticated, carried both Reinvention - As I Lay Dying - A Long March: The First Recordings and non-dun1 genes.
The location of TBX3 expression may also determine the striping pattern of zebras. Both non-dun1 and non-dun2 are found in a region of equine chromosome 8 whose only gene is TBX3.
Non-dun1 has a guanine where dun has an adenine at chromosome 8 base pair 18,, which appears to be sufficient to cause non-dun1 coloration. In addition, non-dun1 has another single nucleotide polymorphism compared to the version of dun that is most common in domestic horses, where a guanine in dun is replaced with thymine in non-dun1 at chr. However, that SNP was also found in some dun Estonian native horsesso is not necessary for dun.
Non-dun2 has a 1, bp deletion and another very near 8 bp deletion. Comparison with TBX3 in other species showed that the non-dun2 deletion is a more derived allele.
Nucleotide diversity across the flanking regions of chromosome 8 for the various alleles indicates that the non-dun2 mutation most likely occurred on a chromosome that already had non-dun1. In some hair bulb keratinocytesnon-dun1 and non-dun2 are thought to disrupt the function of a transcriptional enhancer that regulates the expression of TBX3 during hair growth.
The region deleted in non-dun2 is predicted to include binding sites for the transcription factors ALX4 and MSX2which are both known to be involved in hair follicle development. TBX3 was significantly downregulated in non-dun horses compared to dun horses, while the neighboring gene, TBX5was expressed in about the same amount. In dun horses, the pattern of TBX3 expression mirrored the pattern of pigment deposition in the hair, that is, TBX3 was found wherever the pigment wasn't.
TBX3 was not found in the hair cortex keratinocytes from non-dun horses, nor in those from the dorsal stripe of dun horses. However, all of the horses had a thin outer layer of the hair where TBX3 was expressed. This indicates that the hair follicles of dun and non-dun horses have different distributions of pigment producing cells. Keratinocytes expressing KITLG were found all the way around the hair in non-dun horses, but only on the pigmented side in dun horses.
From Wikipedia, the free encyclopedia. See also: Ni**as Dun Started This (AV) - Deuce (27) - Ni**as Dun Started This coat color genetics.
Retrieved Bibcode : PNAS. Smithsonian's National Zoo. February Nature Genetics. Lay summary — Science Daily. UC Davis. May Etalon Diagnostics.
Norwegian Fjord Horse Registry. Retrieved January 20, Cowgirl Magazine. SciLifeLab, Uppsala University. Retrieved June 26, Equine coat colors. Black Ni**as Dun Started This (AV) - Deuce (27) - Ni**as Dun Started This also known as Sorrel. Bay Seal brown. Dominant white Sabino-white Lethal white syndrome.
Horse markings and patterns. Base color variations primarily UK English. Piebald Skewbald Tricoloured. Varnish roan See also Appaloosa and Knabstrupper.
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