Gene Layering

Acting in Groups

In trying to understand how horse colors are 'made' I find it easier to remember that ALL horses have one of two base colors: EE or Ee - black, and ee - red (sorrel/chestnut). Every other color starts with one of these 'base' coats and then builds on top (or layers) depending on what other genes are present. There really is no such thing as a 'bay' gene, or a 'buckskin' gene, it is multiple genes in harmony, singing along together to produce these and other colors.

So, lets start with the most basic color, sorrel, and 'layer' the other genes on top  and show what some of the colors may be.

Layering with a Red base coat:

Red Family - no black points

Sorrel is: ee, all other genes are recessive (except for color variation genes).

Palomino is: ee, Ccr (sorrel with creme gene)

Red Dun is: ee, Dd (sorrel with dun gene)

Red Roan is: ee, Rr (sorrel with roan gene)

Dunalino is ee, Ccr, Dd (sorrel with creme and dun gene)

There are more, but this is the general idea. In addition, the above colors can have Aa or AA or aa in the agouti (bay modifier) spot and not really affect coat color, beyond a color variation (? See the Chestnut/Sorrel page).

The basic black color (check for the definition used for this site on the Horse Color Explained Page) can be expressed using EE or Ee. Horses with EE genes will not produce sorrel foals because E is always dominant to e and therefore they will not have a foal that is ee or sorrel/chestnut.

Layering with a black base coat:

Black Family - black mane and tail at least

Black is Ee or EE, (for the moment we will go with EE for the layering)

Smokey or Golden Black is: EE, CcrC, (black with cremello gene, but looks black or off black)

Grullo is: EE, Dd (black with dun gene)

Blue Roan is: EE Rr (black with roan gene)

Adding the agouti (A) gene to the black base coat:

Bay is AA, EE, (Black with agouti gene aka bay modifier)

Buckskin is: AA, EE, CcrC, (bay with cremello gene)

Dun is: AA, EE, Dd (bay with dun gene)

Roan is: AA, EE Rr (bay with roan gene, red body, black points)

At this point you need to have a good understanding what is happening above to understand what happens when you cross these colors.

So think about the colors you have seen, and what genes in combination make them up.

Probably the strangest one I can think of was a Buckskin, Tobiano, Appaloosa! The genetic make-up of this horse was something like: A-, E-, CCcr, rr, dd, gg, Tt, Alp alp.