Equine Genetics, like all genetics is a blueprint of what makes the animal what it is. All your horses genetic makeup, their eyecolor, size, hair color, the size of the nose, teeth, and much more is all written in their genetic makeup or DNA.

All genetic material comes from chromosomes. Which means DNA mixed with proteins to form a tightly wound genetic molecule. There are thirty two pairs of chromosomes in a horse, these chromosomes are made up of smaller parts called genes. Each gene is found in the same spot on the same chromosome of every horse.

These genes are not just randomly placed on the chromosomes, each gene has its own spot on the chromosome. This particular spot where the gene is located is called its locus. Or the plural for locus is loci.

There are different variations of genes which are called alleles. One example would be the genetic make up of a gray horse, there is a gray gene, either G or g. One allele, G is the gray:on' gene, which will make up the gray horse. The "g" stands for gray:off' allele of the gene, meaning the horse is not gray. Its code for non gray horse.

The capital or uncapital letters stand for a different type of gene, the capital is dominant and the uncapital is recessive. Dominant=on, Recessive=off. In most cases when writing about a horse you would only write about its dominant genes, mainly because they are the ones that show up in the horses coloring. If someone says a horse is a chestnut, ee, this doesn't necessarily mean she only has these two genes. A chestnut horse also has a gg, which are two gray off genes and every other 'off" gene. This is a given and does not need to be written.

Another term to understand in genetics is "phenotype", this is what a horse looks like. A "genotype" is what is his genetic makeup. Two horses with identical phenotypes, or phyical colors, can have different genotypes, or genes.

Genes are either dominant or recessive, with some genes being more dominant than others. They will override the other genes and basically have the final say in what the horse will look like. Recessive genes may be overridden by dominant genes, if the dominant genes exist in the horse. Chestnut is the most recessive color being overridden by all the other colors. What this states is that a chestnut horse will have no dominant genes 'on' only his chestnut genes. Otherwise he wouldn't be chestnut, he would have been overridden and become a different color horse. Chestnut bred to chestnut always gives a chestnut since those are the only 'on' genes they have to pass on.

The most dominant color is gray. Gray will overide every other color, even if the horse has every other gene, and just one gray, the gray will be dominant and you will have a gray horse. Every gray horse has a gray parent. You can't get gray from non-gray parents because its the most dominant gene, and horses cannot have a hidden gray gene, because if they had a gray gene, they would be a gray horse.

Now every horse has two alleles of a gene. Most chromosomes come in pairs, one from each parent. On each chromosome is a locus for a specific gene, for example a gray gene. This means there are two total loci for each gene in the horse.

Since every horse has two loci for any gene, this means that they can have both the same alleles at each loci, or different. This means that a gray horse could be Gg or GG and just by looking at him you would not know which. He could have one or two dominant gray genes. A non-gray horse is gg, he does not have a gray gene, so he will not be gray.

A horse that has two alleles of the same gene is called homozygous. Both of her genes are the same, so this means she will be sure to pass them on, this is all she can do as she has no others to pass on.