Base Colors and Color Genes 101

[muttduck]

I am going to START to put this together. It is in NO WAY complete. I will edit to add more genes as I develop graphics to go along with them. Also, If anyone has any conflicting evidence that I am wrong, PM me so I can change this post.

To prevent confusion as to sorrel and chestnut, etc... they are referred to here as Red, as they are the same gene, just different shades.

I am adding links (to one of my favorite color places) so you can see examples of each gene.

((FYI, in case you didn't notice yet... All black based colors face to the right in the illustrations, and all red based colors face to the left.))

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FIRST AND MOST IMPORTANT:
All horses carry a pair of genes in each catagory. One part came from it's mom, and the other one came from it's dad. THIS IS ALWAYS. No ifs, ands, or buts.

If your horse does not exhibit any traits from that particular catagory, it is because it has the recessive version of the gene, or has a "lack of" whatever that gene does. There is no way a recessive gene will pass on the dominant version, unless the horse it's bred to carries the dominant gene.

"Homozygous" means two alike genes in the pair for that catagory, either both dominent, or both recessive.

"Heterozygous" means two opposite genes in the pair, meaning one dominant and one recessive.

In most heterozygous pairings, the dominant gene will hide the effects (or ineffects) of the recessive gene.

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The Primary Base Color Gene:
"Eumelanin Gene", E/e
Underneath all of the paint and polish, your horse is one of two base colors, Black or Red. The determining factor for your horse's base is the "Eumelanin Gene" Abbreviated as E in the dominant form, or e in the recessive form. E is the Black coloration. e is the "lack of black coloration" (meaning red.)
In Heterozygous combinations Ee the horse has a black gene, and it will hide the red gene.
In Homozygous pairings, EE will be Black, and ee will be red.

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Modifiers:
Modifiers are what changes your horse from Black or Red to any other color imaginable in a horse.
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The Agouti Modifier, A/a
The agouti modifier is most commonly referred to as the Bay modifier.
The agouti modifier only affects horses with a black base. It can be carried by a red based horse, you just won't see it. (It's offspring, however may show it...)
The Agouti modifier in dominant form A simply removes the black pigment from the main body areas (remember, lack of black = red.) It leaves the black on the legs, mane, tail, muzzle and sometimes ear tips.
The recessive form, a is a "lack of the Agouti modifer", meaning it can't modify the horse.
This is the dominant A Agouti modifier's affects on the black and red bases:

http://www.mustangs4us.com/Horse%20Colors/agouti.htm
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From this point on, we will refer to Bay as part of the bases. Remember, it is simply a modified black.

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Cream Dilution Gene, Cr/cr
Cr the dominant form of the Cream gene, dilutes the coat color. cr the recessive cream gene, is the "lack of cream", meaning, it does not dilute the coat, and cannot pass the dilution onto its offspring.

Think of the cream gene as a bottle of bleach.

In a mild form (Heterozygous, Cr/cr) the cream gene ONLY dilutes the RED pigments. On the three above colors, a single dominant Cr gene would create:
"Smokey Black" A black colored horse CARRYING the Cr gene, but not showing it, since it does not have a red colored coat to dilute.
"Buckskin" A bay horse that has had it's red areas bleached into varying shade of yellow/tan, keeping the black points.
"Palomino" A red horse whose entire body has been diluted to the yellow/tan.


In a more concentrated dominant form, (Homozygous Cr/Cr) ALL pigments on the horse are diluted. Black color becomes a pale rusty color, and the red becomes pale off white, light cream.
In homozygous form, on the above original three colors, we would get:
"Smokey Cream" A black horse, with a double dose of bleach, fading him into a rusty cream color.
"Perlino" A bay horse with the black points being diluted to rust, and the red colored body being diluted to the off white.
"Cremello" A red horse, doubly diluted to an off white coloration.
**Side Note** Most Homozygous CrCr horses exhibit blue or greenish-blue colored eyes.

http://www.mustangs4us.com/Horse%20C...creme_gene.htm
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Dun Dilution Gene, D/d
The Dun gene in its dominant form D dilutes the coloration of both black based horses and red based horses. The D gene will do the same level of dilution whether it is in Heterozygous form or in Homozygous form. There is no "extra strength" dilution by Dun.
The recessive d simply means a "Lack of Dun" and the horse will not have dun characteristics, nor pass them on to offspring.
Dilution effects are on the main part of the body, and dilutes the original shade to a lighter color, leaving the original shade on the legs, muzzle, ears, mane and tail. Dun is also characterized by the distinct "Dorsal Stripe." This stripe is the original shade of color, matching that of the other points, and runs from the base of the mane, to the base of the tail. Dun horses MUST HAVE this stripe to be considered Dun. Other "Dun Factor" markings include the shoulder cross, bars along the dorsal stripe, cobwebbing on the legs and forehead.

Dun can affect any of the colors on a horse, but are mainly found on these:


Dun on black = Grulla / Grullo
Dun on bay = Bay Dun, (commonly called Zebra Dun, or just Dun.)
Dun on red = Red Dun
Dun on Buckskin = Dunskin
Dun on Palomino = Dunalino

http://www.mustangs4us.com/Horse%20Colors/dun.htm
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Champagne Dilution Gene, Ch/ch

This is another dilution gene, yet remains mysterious. Since I am learning about this one, I will add this one with time.

http://www.mustangs4us.com/Horse%20Colors/champagne.htm
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Grey Modifier Gene, G/g
Grey is a gene that some consider as a "color-replacer" since dominant grey G foals are born with color. Grey hairs begin to replace the colored hair within the first year. Grey is a gene that only needs one dominant gene to take its effect, and homozygous grey results in the same changes as heterozygous.
Recessive g simply means a "lack of grey" and the horse does not turn grey, it retains it's birth color, and will not pass the dominant G to any of its offspring.

For a horse to be grey, it MUST have inherited a G from one or both of its parents. (Put it this way, to get a G a parent has to give it to them. If mom or dad don't have a G, and only have g, then the foal will not be grey.)
All greys turn grey by the same means, but due to unknown factors in genetics, some take longer, others shorter, some keep dark points, some don't. Greys also tend to go through phases of color as they slowly gain more white hairs.

In the early and intermediate stages of the graying process, horses will have a mixture of white and dark hairs. Greys are commonly confused with roans when they begin to change. The easiest tell-tale sign is: roans do not get the roan coloration on their heads, and grey will primarily begin to take effect around the eyes, muzzle, ears.


Then they begin to change, and the next phase can still be mistaken for roan. Usually, red based horses tend to turn to a rose grey, and black based horses tend ro go steel grey.


This tends to be followed by a dappled grey phase. By now you know it's grey, not roan.


Then there is the "White" phase. This is where ALL color has now been replaced by grey/white hair.


Last is the flea-bitten stage. This is where a horse has changed to white or near white, and begins to have small flecks of color return into the coat.


http://www.mustangs4us.com/Horse%20Colors/grey.htm
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PATTERN GENES:
The site I will be using as the basis of this is the following: http://www.unicornerfarm.com/basicgen.htm


In simple form, Genes that create white markings are actually genes that prevent color from being 'applied' to areas of the horse while the horse is still in the embryonic stage.

Color cells are formed, and then migrate over the skin and cover the horse. Some genes either prevent the building of enough color cells to cover the whole horse, or prevent them from migrating to certain areas. Each gene controls the color cells differently, hence the different patterns the genes display.

Tobiano is one of these such genes.

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Tobiano Pattern Gene, To/to

The Tobiano Pattern gene in its dominant form To creates white areas on the coats of both black based horses and red based horses. The To gene behaves the same, whether it is in Heterozygous (Toto) form or in Homozygous (ToTo) form.
The recessive toto simply means a "Lack of Tobiano" and the horse will not have Tobiano Pattern characteristics, nor pass them on to offspring. In other words, the horse is a solid.

Tobiano can effect all coat colors (excluding White), regardless of base, dilution, or modifier.

However, not all Tobiano horses will be "loud" Tobianos. Some may only exhibit smaller areas of white, while others have large areas of white.

The following graphic is a diagram of various Tobiano Patterns, both minimally marked, and loudly marked. All of which are possibilities when breeding Tobiano Patterned horses.



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WILL BE EDITTED TO ADD:
Roan, Pearl, Silver Dapple...

HOPE TO ADD IN THE FUTURE:
Overo, Tovero, Appaloosa Patterns, Dominent White, and more!!!

[Laskiblue]

Hey, Muttduck, that's a great start! That's the most understandable explanation of horse colors and basic genetics I've ever seen. Looking forward to more . . .

Laskiblue

[EK'S MA]

Muttduck, this is great! Can't wait til you get to Grey, I have a ton of questions on one I have and the more I try to study the genetics and dillutes the more confused I get, so I'm hoping you have the explanation(in english) that I've been searching for.
EK'S MA

[muttduck]

I had those first ones already saved, so now it comes down to having to get horses colored as I go along. Slowly, but surely, I'll get to them!!

[Rocking Horse]

Muttduck:

You never cease to amaze me

Just think: We both move to KY with the Divine One, I take my road trip, you do the Illustrations and DME does the writing... Bestseller
Plus we can have ALL the colors between us

Karen

[muttduck]

Originally Posted by EK'S MA

Muttduck, this is great! Can't wait til you get to Grey, I have a ton of questions on one I have and the more I try to study the genetics and dillutes the more confused I get, so I'm hoping you have the explanation(in english) that I've been searching for.
EK'S MA

I just added Grey, so hopefully it will answer some questions.

[EquineAlberta]

I love the explainations and diagrams!

One step with the greys that isn't really in the step by step greying process, is that chestnuts will sometimes grow in a black mane and tail while going grey. I have never quite understood that one, although I am not sure that all chestnuts do that.

Great work!

Karen2

[EK'S MA]

Okay Muttduck, so this is where I get really confused, in order for a horse to be grey one of his parents must be grey- so a chestnut (looks black) out of a chestnut & grey would only carry the recessive g gene, right? And a buckskin who is out of a buckskin and a palomino, would not carry a g gene at all. So the resulting colt could not be grey. Here are a couple pic's of the colt he was born palomino but now???? Thanks for your help.




<editted by muttduck. I made your pics smaller for you. >

[EK'S MA]

Sorry I forgot to shrink the pic's before I posted
EK'S MA

[ToveroMom]

Looks like dapples to me..

[muttduck]

Originally Posted by EK'S MA

so a chestnut (looks black) out of a chestnut & grey would only carry the recessive g gene, right? And a buckskin who is out of a buckskin and a palomino, would not carry a g gene at all. So the resulting colt could not be grey. Here are a couple pic's of the colt he was born palomino but now???? Thanks for your help.

I'm busting out the confusing language....

Remember, that all horses have a pair of genes from every catagory shown above. One side of the pair is given to them by their dad, the other side of the pair is given to them by their mom.

All horses are either GG, Gg, or gg.

GG is homozygous grey, meaning this horse is grey colored and will always have a grey foal.
Gg is heterozygous grey, meaning this horse is grey colored and has a 50/50 shot of grey foals.
gg is homozygous "lack of Grey" or in other words this horse is not grey and has no shot of a grey foal (unless bred to a grey horse, and that horse gives the G gene.)

If the horse is carrying the G gene it WILL grey his coat. "If it is inside, then it is on the hide" so to speak. There is not a "hidden grey" and it won't "pop up" two generations later.
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On the first pairing, Chestnut and a Grey produced a "looks black Chestnut." I will stick to the main color focus...

The chestnut parent will pass an e (lack of black) gene, and a g (lack of grey) gene to the foal.
Think of the grey parent this way...
Underneath that grey layer is another color. Whatever color THAT was can also influence the coat of the foal.
IF the grey parent was a black based horse under the grey, then the black gene E can be why you have a black looking foal.
If the grey parent was heterozygous Gg, it might have given the foal the G (foal goes grey), or it might have given the foal the g (foal doesn't go grey.)
If it doesn't go grey, then you know your foal is not carrying a G, and will never have Grey foals, unless bred to a grey and that grey passes the G.
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On the second pair...
If Dad was buckskin, and not grey, then Dad is gg. He gives one of his g genes to the foal.
If mom was palomino, and not grey, then Mom is gg. She gives one of her g genes to the foal.
Now the foal has one g from Dad, and one g from Mom.
And that makes the foal gg, homozygous "not grey."

Now, looking at your pics, and from your info, I'd say he's a bleached out Pally. Being in the sun is giving him the "white" look.
The clear defined facial markings help determine as well. Greys tend to "lose" the definition of facial marks, and the white edges "bleed" slowly into the color quite early in the greying process.

I am also guessing that there may be another gene playing as well...

Sooty/Smutty can be responsible for the darker areas and possibly the dappled effect. Sooty changes with the seasons, another reason it seems to be just apparent now, and not earlier.
Check this link out and scroll down to "Benny" the buckskin... In the "spring" photo he looks to have similar shading and dappling along his neck that you are seeing.
http://www.mustangs4us.com/Horse%20Colors/sooty.htm

[EK'S MA]

Thanks Muttduck, I think I understand the bottom line is he is NOT and will NOT be grey. This poor colt just can't seem to decide what he wants to be when he grows up. This is the 3rd color in his 3months of life, maybe next month he'll be a dun at least I understand that color. Thanks again
EK'S MA

[treasure1]

This was excellent thanks for putting all the time into the reserch, it realy made it easy to understand

[OSUJillyBean]

Thanks MD! I was about to get on HT and ask for a reference guide to genetics since I'll be starting that class in about a month. I like your intro to genetics. Makes a lot of sense!

*hugs for all your hard work*

[debymcw]

FIRST AND MOST IMPORTANT:
All horses carry a pair of genes in each catagory. One part came from it's mom, and the other one came from it's dad. THIS IS ALWAYS. No ifs, ands, or buts.

Hi its me again with that EE tobiano.
I am reading your 101 LOL
when you refer to each category-what are the catergories?
DOes ever horses genetic code include E's A's C' ect?
SO that with him being EE he can still carry the dun but just in a recessive form, that being EE doesnt mean he cant carry agouti or dun as well?

His sire is black tobi and dam is grulla tobi so he ends up being EE but can still carry the dun recesively?

[Orchid]

Hmmm, where to start.

You can think of every horse's genetic code as having a pair of each letter. For instance, if you have a homozygous black tobiano, his code would look like this:

EE aa CC dd gg ww toto

Meaning: EE two black genes
aa no agouti genes
CC no cream genes - cream genes are Ccr
dd no dun genes
gg no grey genes
TOTO two tobiano genes

Dun is not a gene that is carried in recessive form - if he had a dun gene, it would show up on his coat. Same with grey and agouti. A cream gene will always show up on a bay or a red horse, but one cream gene will not show up on a black horse - hence the smokey black that throws a "surprise" palomino with a red horse.

An EE horse can carry dun (Dd or DD) or agouti (Aa or AA) - but then he would be either a dun or a bay. So, he would still be homozygous for black, and still would not throw red foals.

Does that make any sense?

[WYJumper]

Doesn't a upper case letter mean it is not something (like a GG= not gray) and lower case letters mean it is something (like gg= is gray?)

Wow, did that make any sense?

[Orchid]

Other way around - except in the case of cream, which is denoted as:

CC - no cream gene

CcrC - one cream gene

CcrCcr - two cream genes (the little cr is supposed to be a superscript, but I don't know how to do that here)

But, normally it is like this:

gg - not grey

Gg - heterozygous for grey

GG - homozygous for grey

Check out this table Steph, it is an oldie but should help:

http://www.vgl.ucdavis.edu/research/...lon/coats.html

[WYJumper]

Thanks Orchid!

I think maybe the chicken people have it backwards. They are always saying BL means not blue and bl means blue.

[Country Lady]

I think I have it figured out I should get a red dun foal from a reddish chestnut stallion and a red dun mare??? And same stallion and lineback buckskin mare could get red dun, buckskin or dunskin??? My luck both will be sorrel.

Thank-you