Dun gene

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see Dun (color) for images and general information on this color.

Dun coloring

The dun gene is one of the dilution genes that affects both red and black pigments in a horse's coat color. Unlike the silver dapple gene (which works only on black-based coats) or the creme gene (which works on red-based coats), it has the ability to affect the appearance of all black, bay, or chestnut (red) based horses to some degree. The gene affects coat color by turning black on certain areas to chocolate or a slate grey colour, and red on certain areas to a golden or beige colour.

The dun allele is a simple dominant allele, so that the phenotype of a horse with either one copy or two copies of the dun allele is dun. A horse with two non-dun alleles is just that, not dun.

See Equine coat color genetics to compare the genes.

1 Dun vs buckskin
2 Shades of dun
3 Breeding and the dun gene
4 References
5 See also
6 External links

[edit] Dun vs buckskin

Since dun can closely resemble buckskin when it is on a bay-based (black base + Agouti gene) horse, it is in some cultures confused with buckskin. The difference between these two genes is that the dun gene also causes "primitive" markings, and a different shade of body colour. These primitive markings are usually a shade or two darker than the body color. Primitive markings include:

Shoulder blade stripes
Dorsal stripe
Zebra stripes on legs
Cob webbing

However, dorsal striping does not guarantee that the horse carries the dun gene. The counter-shading gene can also produce dorsal striping in breeds such as the Arabian and the Thoroughbred, where the "dun" dilution gene does not exist in the gene pool.

Note: Unlike the dun dilution gene, the creme gene does exist in Thoroughbreds. [1], [2]

[edit] Shades of dun

Zebra dun

The dun gene seems to have more concentration in the body than the mane, tail, legs and head, and so lightens the body coat more. This would explain why points on a dun are a shade darker than the coat, or in the case of a zebra dun, the mane, tail, and legs are not diluted much at all. The zebra duns have the "buckskin" look to them: tan body color with black points, plus the primitive markings. Their coat, however, is usually more tan than the yellow of most buckskins. Red dun colored horses do not have the black points, and they are usually grouped together and called Red Duns. Grullo (GREW-yo, or Grulla, GREW-ya for females), mouse duns or blue duns have a smoky, bluish, or mouse-brown color and can vary from light to dark. They consistently have black points and they often have a dark or black head, which is an identifying characteristic of the this group. The primitive markings are usually all black.

[edit] Breeding and the dun gene

Red base + Dun= Red Dun (it is because they are red-based that they don't have black points of the Zebra Dun). Less common than Zebra/bay Duns, more than Grullos
Black base + Dun= Blue dun, mouse dun or Grullo/Grulla.
Bay (black base = Agouti gene)= Zebra Dun/ Bay Dun.

The three different dun varieties usually occur in proportion to the occurrence of the corresponding base colours in each particular breed.

[edit] References

Bowling, Ann T. "Coat Color Genetics: Positive Horse Identification" from Veterinary Genetics Laboratory, School of Veterinary Medicine, University of California, Davis. Web site accessed February 9, 2007