Joanne
Well-Known Member
This article just came out today online at The Horse.com
Here is a small portion of the article discussing the silver gene:
To read the entire article which covers many color genes, here is the link:
The Horse.com Article
Here is a small portion of the article discussing the silver gene:
Another example of a coat color gene associated with health problems is the silver dilution, which can be associated with an eye defect known as anterior segment dysgenesis (ASD), a genetic malformation of the anterior segment of the eye that causes development of cysts, misshapen pupils, and defects of the iris, cornea, and lens.
The association between the silver gene and ASD has been documented and studied in the Rocky Mountain Horse breed in which silver-diluted colors are prevalent. Silver dilution is also present in other horse and pony breeds such as Miniature, Icelandic, Morgan, and Shetland, and there are indications that ASD may not be restricted to Rocky Mountain Horses.
While there is a clear association between the silver gene and ASD, the specific mechanism leading to the eye defect is not known. It is hypothesized that ASD is caused by a gene located near the gene controlling the silver dilution, and that selection for silver-colored breeding pairs increased the incidence of ASD over time through a "hitch-hiking" effect. Because the silver color is highly desired in the Rocky Mountain breed, ASD presents a particular challenge to these breeders.
While the silver gene might not directly cause ASD, the silver coat color is associated with ASD in Rocky Mountain Horses, perhaps because the gene causing ASD is located near the silver gene and has been propagated with the color in this breed. A genetic test for silver is available through the VGL, but because the genetic basis of ASD has not been identified, horses cannot yet be DNA tested for the disease itself.
To read the entire article which covers many color genes, here is the link:
The Horse.com Article