It's not complete. ^^' But it does cover some of the basics of the basics xD

1. Horse Genetics A creative communications presentation by Katelynn Olney

2. The Basics Every gene is contained on an allele. Every allele controls a different pattern, color, or modifier. Every allele is on a Locus. Every locus contains all the genes which control a certain pattern, color, or modifier. For example, the A locus contains all the alleles which modify the “A” color. Important to remember: Each loci is its own. The A locus is not dominant or recessive to the B locus, for example. The colors on the E locus, or extension Locus, are modified by all the other loci.

3. The Basics (continued) Breeding and Genes In genetics, genes are either dominant or recessive. One gene is received from the other, the other from the father. For example, If a horse is Ee, the father gave the foal one E, the mother gave one e. Dominant and Recessive. Dominant genes are “dominant” over recessive. Meaning, if E is dominant over e, and a horse gets one E from dad, and one e from mom, the E would show up and the e would not.A good example is blue eyes. If your mother has blue eyes, and your father has brown eyes, you’ll most likely end up with brown eyes. Brown is dominant over blue. In humans, anyway.

4. The Bases, I All horses start out either chestnut, or black. Chestnut Is produced by a chemical called phaeomelanin.  Black Is produced by a chemical called eumelanin.

5. The Bases, II The E (extension) Locus The E locus contains the alleles for the base colors. There are three alleles on the E locus. E+ triggers the release of a pigment called eumelanin. Eumelanin turns a horse black. E+ is dominant over e and ea. E+: eand ea: e and ea trigger the production of phaeomelanin. This causes a chestnut pigmentation to form. It is recessive to E+. True Black and the Red Factor faux. Because horses inherit one gene from their mother, and one gene from their father, and because black (or E+) is dominant over e and ea (or chestnut), horses can be E+ e, or E+ ea. This means that they appear to be black, but are carriers of the chestnut gene. This hidden chestnut on a horse is sometimes referred to as a “red factor”. Because the horses have this red factor, sometimes breeding two black horses together will result in a chestnut foal. Only the breeding of two E+ E+ horses, or “true blacks” has a 100% chance of producing a black foal. E+e or E+ea horses which are bred to another E+e or E+ea horse has a 50% chance of producing black or a chestnut. Breeding an E+E+ horse to and E+e or E+ea horse has a 25% chance of resulting in a chestnut foal, or 75% chance of producing a black.

6. The Modifiers, I The A Locus The “A” in A locus stands for Agouti, which is a certain gene. The agouti gene adds black pigmentation to the base colors, chestnut and black. The A locus contains 4 alleles. The recessive: Aa and At are recessive. Despite being recessive, they actually add more black to a horse than their dominant counterparts. Horses which are homozygous for Aa will actually, sometimes, show black. The dominant: AA and A+ are the two dominant genes on the A locus. Despite being “dominant”, these genes actually add very little black pigmentation to the horse. Homozygous A+ horses are some of the palest horses you can get, barring any cream genes or dilutions. Now, lets see what the colors do to the bases...

7. The Modifiers, I Chestnut, the A locus, and you. The A gene on a chestnut will result in the following colors: AtAton chestnut results in standard chestnut: A+A+ on chestnut results in light chestnut: AaAa on chestnut results in liver chestnut: AAAA on chestnut results in red chestnut: