Post by SydneyandStorm on Feb 16, 2013 16:52:47 GMT -6
Overview
Genetics are very important for most animal owners, especially breeders. They determine the color and breed of each animal, as well as alerting breeders to potential lethal disorders before they take place. Animals are required to be DNA tested before they are bred. This is done automatically for horses born at Saunders Ranch and New York Riding Stables and for a fee of $500 if bought from another place. The tests will only cover colors and potential lethal disorders.
- Homozygous means that a trait has two alleles that are exactly the same for a gene, such as AA or aa. Heterozygous means that one allele is dominant (represented by a capital letter) and one is recessive (represented by a lowercase letter) such as Aa. A heterozygous trait will always show the dominant form of a trait, but if bred to another heterozygous or a homozygous recessive, may produce a homozygous recessive which will show the recessive form of the trait.
Genetics Summary
While there are hundreds, if not thousands, of genes that can determine everything from the base color of a horse to the number of hairs on its mane, the genetics that we are primarily concerned with are the colors. Here is a brief summary of what they are and what they control:
- Chestnut - chestnut is completely recessive, so it can only have the genes "ee." Two chestnuts can only produce a chestnut, though other colors can carry a chestnut allele, which is a simple "e."
- Black - black is the second most recessive color, next to chestnut. To be black, a horse needs only one "E"; homozygous blacks, "EE", and heterozygous blacks, "Ee", look the same.
- Agouti - this is the gene that acts on black horses to restrict their color to certain points, creating a bay. Its allele is "A" or "a" and it can come in the form of "AA", "Aa", or "aa." Black horses can only carry the "aa" gene, while chestnuts are unaffected by agouti. It is also responsible for producing a seal brown or brown horse with the allele "At."
- Cream - the cream gene is what is known as an incomplete dominant trait, so horses that are heterozygous look different from homozygous dominant horses. It is represented by either "CR" or "cr" and is responsible for palominos, buckskins, smoky blacks, cremellos, perlinos, and smoky creams. Palominos and cremellos are both chestnuts with either one or two dominant cream alleles, palominos with one and cremellos with two. Buckskins and perlinos are bays with one and two dominant cream alleles, respectively. Smoky black and smoky cream are horses with a black base and one or two dominant cream alleles, also respectively, though a smoky black can look identical to a normal black horse as the cream gene will only dilute red.
- Dun - the dun gene basically lightens a horse's coat, except for a stripe down the horse's back known as a dorsal stripe and leaves primitive striping on the horse's legs. The mane and tail are also left the original color. Dun on a bay horse will create the most commonly known yellow dun, while dun on chestnut will create a red dun and dun on black will cause the color grulla. The allele for dun is "D" or "d."
- Gray - gray is not an actual base color but a pattern characterized by a horse whose base color is eventually covered by a shade of gray. It can act on any coat color. Homozygous dominant and heterozygous grays both look the same, as only one allele needs to be dominant for the gray to mask the base color. It is represented by a "G" or "g."
- Silver - silver, unlike cream, will only dilute black, and its allele is either "Z" or "z." Silver on black can create classic silver dapple, chocolate silver, or blue silver, silver on bay will produce red silver, and silver on buckskin will dilute the black pigment to a light brown. It has no effect on chestnut horses. Do not be misled - the silver gene does not cause the horse to be colored silver. It simply lightens black pigment.
- Champagne - champagne lightens a horse's coat and its allele is "Ch" or "ch." Champagne on black is called classic champagne, champagne on chestnut is gold champagne, and champagne on bay is classic champagne. Champagne on any cream horse is (color of champagne of base coat) cream champagne.
- Roan - roan horses consist of a base color with white hairs scattered all over the place, which creates a ticked look. The allele for roan is "Rn." A chestnut with roaning will create a red roan, a black with roaning will create a blue roan, and a bay horse with roaning is a bay roan. Some people consider homozygous dominant roan (RnRn) to be lethal, but recent experiments have proven this to be incorrect.
There are many other colors, but these are some of the most common. If you have any other questions, feel free to ask away and I will do my best to answer them!