Every horse has two of the BASIC color genes - red and black. A horse is either red-based or black-based. In addition it can have modifying genes like agouti, gray, dun, or creme.
Black based colors are black, bay, buckskin, brown, perlino.
Red based colors are palomino, chestnut , cremello.
Every horse will throw one gene from their basic color makeup.
Red Factor gene (really it is an Alelle which is a portion of a gene but for simplicity I'm going to call them genes) (chestnut) is written as a small e.
Black factor gene is written as a capital E.
For instance a chestnut is ee - meaning it will always throw the chestnut gene. That is why chestnut bred to chestnut always equals chestnut. The sire throws one e gene and the dam throws one e gene resulting in a ee foal.
A bay horse is E (the black gene) and the second gene can be the chestnut gene e. The black gene E is dominant and will always express itself over the red e gene. A bay horse has a 3rd gene, the agouti gene which is A . Agouti restricts the black to the points (ie legs, mane, tip of the ears etc) So a Bay horse can be Ee Aa (meaning it is neither homozygous for Black nor for Agouti). A bay horse can be homozygous for bay and would be EE AA and could only produce a bay.
A black horse has the E gene but NO agouti. A homozygous black horse would be EE aa. A black horse who could produce chestnut would be Ee aa, meaning it can pass on the e gene instead of the E gene.
Now we come to the dilutes (creme) which are written as CR. A dilute gene 'fades' the color of the horse.
A palomino is a chestnut with one creme gene. ee CR
A buckskin is a bay horse with a creme gene -- Ee Aa CR. In this case the horse could produce a palomino, a buckskin, a smoky black (remember black is dominant so it's not diluted but the horse will carry the creme gene) or bred to another creme carrying horse it could have a cremello or perlino.
The cremellos and perlinos are double dilutes meaning they have two creme genes CR CR and are homzygous for creme and will always pass it on. A cremello is a double dilute chestnut ee CR CR and a perlino is a double dilute bay horse which can have several combinations, ie Ee Aa CR CR or EE AA CR CR (homozygous black and homozygous agouti).
Merideth Sears - MeridethinWyoming
AFS Morgans @ http://www.afsmorgans.8m.com