Cream gene
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The cream gene is a dilution gene expressed in horses, and produces lighter colors. When one copy of the gene is present, it dilutes "red" color (chestnut) to yellow or gold, but not black color. When two copies of the gene are present, both red and black hairs become a paler color; red hairs become cream or white, black hairs become reddish.
Cream horses are not "white" horses. Dilution coloring also is not related to frame overcoat patterns or lethal white syndrome, does not produce white horses nor is cream related to the controversial "white" or "dominant white" (W) gene.
Dun color is produced by a separate dun gene that acts upon a base coat color to produce a different form of color dilution, along with distinctive markings.
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[edit] Colors produced by the cream gene
The cream gene produces the colors:
[edit] What it does
The cream gene is an "incomplete dominant" gene, which means that it is expressed to some degree even when there is only one copy of the gene--it is dominant--but it expresses itself even more when there are two copies (one from each parent).
Coat color: The cream gene lightens the base coat. One copy lightens red (chestnut) coloring to pale yellow or gold, such as palomino, but does not overtly affect black color. Two copies will lighten both red and black hairs.
Eye color: double dilutes have blue eyes (unlike brown eyes of a gray and some white horses). Depending on the genes carried by the other parent, a single dilute, such as a Palomino, can be born with blueish brown eyes and pinkish skin that darkens after birth, or may be born with dark eyes and skin.
[edit] Single dilutes
Single dilutes receive the cream dilution gene from only one parent. The other parent does not carry the dilution gene.
Palomino: One parent genetically contributes the creme gene, and both parents contribute a "red" base coat gene. The creme gene lightens the coat to pale yellow/ gold and the mane to white, producing a palomino.
Buckskin: One parent genetically contributes the creme gene, and one or both passes on the genes for bay (the black base gene and the agouti gene that restricts the black to the points only. (see bay) for explanation of the agouti gene). The creme gene lightened the coat to pale yellow, but could not change the black of the horse, leaving the mane, tail, and lower legs black.
Smoky black: One parent gives the creme gene, and one of both passes the gene for a "black" base color. One creme gene cannot change the black hairs, so the horse looks black, "masking" the creme gene. Only on true blacks can the creme gene be totally masked. Those horses with some brown or red hairs will have those hairs turned gold, and have a "glow" on their coat. Although the gene is masked, IT CAN STILL BE PASSED ON. So a smoky black stallion can pass on the creme gene to the next generation, and produce, say, a palomino horse from a chestnut mare, even though neither parent appears to have the gene.
[edit] Double dilutes
Double dilutes have 2 creme genes (one from each parent). This even further lightens the red color: from the golden color of one dilute to a pale "creme" color of the double dilute. It also results in lightening of black hairs to a dark cream color.
Double dilutes are not true white horses, nor are they albinos, even though they have pink skin. There are no true albinos in the horse world.
Nor are double-dilutes gray: they have blue eyes and pink skin, whereas a gray horse has dark eyes and black skin.
Cremello: The double dilution of chestnut/red coats. The body and mane is a cream color (hence the "cream gene").
Perlino: Double dilution of bay, so that the body is a light creme, with "pinkish" points (mane, tail, lower legs).
Cremello and Perlino horses sometimes fade in color as they mature, so that they look almost white but some remain the same pale gold or cream. Their eyes and skin remain their respective colors.
Smoky Cream: Double dilution on a black coat. The cream gene is not completely hidden like it was in the smoky black. The horse is a light gold or cream color and can be difficult to tell from a cremello or perlino(although colors vary). If one wants to be sure of the base color, the horse can be tested for the Red Factor and Agouti gene.
[edit] Color differences
| Color | Coat Color (Birth) | Coat Color (Adult) | Eye Color | Skin Color |
|---|---|---|---|---|
| Gray | Bay, chestnut or black | Grays until White | Brown | Black |
| Cremello | Light Cream, visible markings | May fade to white | Blue | Pink |
| Perlino | Light Cream, visible markings, mane and tail reddish | May fade to white | Blue | Pink |
| White | White | White | Dark | Pink |
| Albino (Lethal in horses)* | White | White | Pink | Pink |
| Ivory** | Light Cream | Pale Cream | Green/Greenish | Pink |
| Champagne | Chestnut or bay | Shades of yellow | Birth: blue, adult: hazel | Pink |
[edit] Other terminology
This dilution gene is sometimes also called the "creme" gene. However the spelling most often used by geneticists, is "cream." "Creme" is actually an abbreviated form of "cremello", which refers specifically two cream genes on a chestnut base.
[edit] See also
- Equine coat color genetics
- Equine coat color
- White (horse)
- Gray (horse)
- Dun (color)
- Albinism
- Leucism
- Champagne gene
- Lethal white syndrome
- To read more on the fatal double dilute white (WW) gene, go to [ http://www.equiworld.net/uk/horsecare/reproduction/colour07.htm White, Albino, and Lethal White Genes]
- To read more on Coat Color Dilution Lethal/Lavendar Foal Syndrome in Arabian horses, seeLavender Foal Syndrome Fact Sheet, Cornell University. and F.O.A.L.
[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
