Genetics concepts - sekelsta/horse-colors GitHub Wiki

Here are some genetics concepts found in Realistic Horse Genetics.

Epistasis

Epistatis is when one gene can hide the effects of another. For example, the e allele of the extension gene is epistatic to the agouti gene. A horse with E at extension will be either bay or black depending on its agouti gene, but a horse with two copies of e will be chestnut regardless of what alleles it has at agouti. It is like the chestnut color from extension hides the bay or black color from agouti.

Genetic linkage

Some genes are found on the same chromosome, and are linked. That means that when a horse breeds, it is much more likely to pass on the same set of alleles that it got from its dam or sire, and much less likely to pass on one from the dam and one from the sire.

Genes that are linked form what is called a "linkage group". Tobiano, chestnut, roan, and KIT (including dominant white and sabino) are all found on equine chromosome 3 and they form a linkage group called equine linkage group II.

Mutations

Mutations are similar to those found in Minecraft, but rarer and with a smaller effect. When the parents pass on their genes, for each allele there is a chance that a mutation happens determined by the mutationChance configuration option. By default the chance is 1/2000. When there is a mutation, one parent's allele is replaced with a random allele out of those that can appear in its species. Each allele in each gene has an independent chance to have a mutation, meaning a single foal can have multiple mutations.

Version history

• Version 1.2.3 introduced chromosome linkage.
• Version 1.2.1 introduced mutations.