Colors, a brief genetic primer

by Leah Patton

Some registries are based on breed type, and disregard color. Many of those are not up on color genetics (not just color trends). The Paint horse Association is unfortunately, one of them. They still have incorrect descriptions of tobiano, and "overo".

The Buckskin Horse Registry is another. Buckskins are now recognized as being bay +cream horses, They may or not have a dorsal - but most do not. A dorsal alone is not a sign of dun, there are a number of factors that make up dun, and duns do not test as creams.

Obviously, some animals will be dun and cream both, but most people can recognize visually (phenotypically) the difference, and the animals will breed as if they are giving both a cream (buckskin) and non-cream dilute (dun) gene.

Dilution genes do just that - dilute the coat color. Some dilutions are weak when paired with black (such as cream). Others do not have an effect on red (such as silver). Some seem to act strangely when paired together. Silver +cream often doesn't have the light mane that we think of with silver. Why? We're not sure.

Dun homozygouts and champagne homozygouts (having two genes for dun or having two genes for champagne, respectively) do not look an different than heterozygous horses, which is the opposite from cream.

So, color throws us a lot of curves. To be able to understand the genes correctly, we have to use correct, concise terminology, for every breed and every situation. Until all breeds are on the same page with the way colors are described, there will be a lot of confusion.

So the basics, in a tiny nutshell

E black
e red

A horse will have either EE, Ee or ee.

Abouti (A) modifies black on the body. There are two known agoutis, but no way commercially at the moment to differentiate between A (bay) or At (Brown). There is most likely another version of Agouti for Wild Type.

Stop a moment and remember that the symbols that geneticists use, and the terms we use, are just ways to twist our minds visually around what is happening. These are not pairs of genes hiding in the cells, they aren't switches, they are chains of proteins that line up in a set order. It's just mind boggling to try and think of it any other way, and this is the accepted way of explaining things.

Having a base color established, you can now add other modifiers to the horse.

Known dilutions are Cream (Cr) Champagne (Ch) Dun (D) Silver (Z) and Pearl (Prl)

Cream +Black - smoky black, usually not visiby different
Cream +Cream +Black - Smoky cream, resembles perlino

Most of us know it from here:

Palomino, cremello, (chestnut base)
Buckskin, Perlino (bay base)
Dark buckskin, perlino or smoky (Brown base, hard to differentiate in many cases)

Gold Champagne (red base), Amber (bay) sable (Brown) Classic (Black).

Add the word Cream (ie Gold Cream) if a horse has one cream and one champagne.

And yes, we know of a number of horses that are perlino and cremello with a champagne gene. Color? WHITE!

Dun is the gene, dun is the dilution. Dun on black is grulla or grullo, dun on bay is zebra dun or Yellow dun (all to frequently just called dun) and dun on chestnut is Red dun. Brown duns can look grullo or zebra dun.

This doesn't even touch on patterns of white such as roan, roaning, rabicano, LP/PATN (Appaloosa) Tobiano, sabino, Frame, splash, Grey, or brindling, birdcatcher spots, Bend Or Spots.

So you can see that this is getting longer and more complicated as we go. So many "switches" to turn on. So many layers. Why do some horses have dorsal stripes, but are not dun? Why do all duns not have leg bars? In most of these cases, it's obvious there are multiple sets of genes paired together to produce a final result.

Could you have a horse that was a black-based bay champagne roan going gray silver dapple tobiano/sabino splashed white? Theoretically, sure. What color would it be? White.

How would that be described on the horse's papers?

The Palomino Horse registry still has horses that are champagne and palomino +dun in the books, even though the rules specifically exclude these horses. Is this helping or hurting color ID?

That's why so many of us are adamant about how a color is described, or what colors can and cannot occur in a breed. That's why we'll be skeptical if we hear of a "purebred" palomino Arabian, since no purebred has ever been proven to carry cream. Find one that passes the parent tests, and the Arabian registry will accept it. But unless a brand-new mutation has occured in that horse, it's not going to happen.

That's the reason that the pres of the ICHR put her foot down when the Iberian horse owners were saying their horses were champagne. Show us a champagne parent, the researchers said. None could be proven, instead, a brand-new, recessive dilution (Pearl) was discovered.

So when you hear of a strange color popping up in a breed, or find a weird example of a horse, remember there are a couple of possibilities. One, the parent info is wrong. Two, the animal actually has a mutation of color/markings. That's when the known genetics tests NEED to be run, to rule out the obvious. People who tell us "I know my horse is a silver dapple because his grandfather was" are just proving they know nothing about color, and don't want to learn. It's sad, but the majority of those cases will pass on the wrong information and keep us churning along in the dark for that much
longer.

PLEASE feel free ALWAYS to ask color questions. If you aren't sure about the color for a model, the parents you want to use for a model, or an example you want to paint from, ask me, or one of the other people who also research color. If we aren't sure, we'll take it to other geneticists. The ICHR group is quite used to "model horse" question popping up in the forums. Promoting correct information about champagnes, in the flesh or in plastic, is quite appreciated in that circle.


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