help understanding genes

[Derby Lyn]

I am looking at a mare that is Ee aa. Can you please help me to understand this? This means she is black, correct? What colors can she throw when bred to black, bay or chestnuts?

From what I am reading off the genetics sight, Ee means that she is black based and the recessive gene is hiding (is recessive gene chestnut?). So she could be bay just from Ee? but the aa makes her a black?

what exactly does the aa mean? I know it means she is not a bay, but what does it mean to her foals? AA and Aa would be bays

[xfactor fan]

Derby Lyn,

You got it the first time.

The mare Ee, aa, shows a black coat color. In horses this needs two independent genes working.

First is Extension (funny names, just go with it) She had E-the dominant version of this gene which produces black pigment. She also carries the recessive e, which produces red pigment.
For her foals she has a 50/50 chance of passing either of these genes on.

Agouti ( named after the mouse color--and the mice have a lot to answer for)
A is the dominant form of the gene and pushes the black color to the outside of the horse resulting in a Bay. Brown body-black points.

a is the recessive form of the gene, and doesn't change the color.

Your mare can only pass on the recessive form of the gene so all her foals will carry Agouti a.


Crossing you mare Ee aa with a black stallion

Two possibilities, first that the stallion carries two copies of the E (black)

So he would be EE aa x Ee aa.

The foals would all be black.

half would be EE aa, and the other half would be Ee aa. But because the all carry the recessive aa, and the dominant E, they would all look black.


Crossed with a chestnut stallion: ee ??

The base coat color would be 50% black, 50% chestnut.

If you know the agouti status of the chestnut stallion (three possibilities here AA Aa aa) but since Agouti only shows up on black coats, the stallion would have to be tested to know for sure).

Of the black based foals they could be

Black aa ,
Bay Aa.

So if the chestnut stallion was ee AA, all the black based foals would be bay.
If the stallion was ee Aa, half the black based foals would be bay, half black
And if the chestnut stallion was ee aa, all the black based foals would be black.


The only trick to this is to remember that the base coat color and Agouti live on different chromosomes, so will be independent of each other. Maybe thinking of them as two coins a penny and a dime. If you toss them at the same time, you might get two heads, but there is no connection between the event.

Good start and hope this helps.

[Derby Lyn]

Thanks, just one question. When you say this:

half would be EE aa, and the other half would be Ee aa. But because the all carry the recessive aa, and the dominant E, they would all look black.

Do they just look black (maybe a black bay?) or are they really black?

[RiddleMeThis]

Thanks, just one question. When you say this:

half would be EE aa, and the other half would be Ee aa. But because the all carry the recessive aa, and the dominant E, they would all look black.

Do they just look black (maybe a black bay?) or are they really black?

E? aa is REALLY black. Now they may not LOOK black (fading etc) but they ARE black. To be a "black bay" they would be "E? A?"

[xfactor fan]

That's a good question, and one that needs more investigation.

There are several genes living at the Agouti address, or near the Agouti address. Agouti A or regular Bay, Wild Bay, Black, and Brown.

Then blacks can be divided into Raven Black ( non fading) These horses tend to have blue black highlights in the sun.

Fading black These guys bleach to a brownish or bayish color

Blacks with a dilute like cream.

Take a look at Donna's Smoky black filly. In photos she looks like a dark bay, but genetically she's black + cream. (aa Cr cr)

Then of course there's nutrition and latitude, the more direct sun the more the horse fades if it is going to fade.

There may have been some studies done on the differences between fading and non-fading black, perhaps someone else can point you in that direction.

My best guess is that the difference is in how the pigment is laid down in the hair shaft itself, and other than someone who's been looking at samples of dun hair, don't know if the genetic control over this has been studied. It should be too, perhaps someone has been looking at the Turkoman horse breeds--ones that "glow" ?

Does you mare fade or not?

[HeadlessHorseman]

I read this a few times....as I am "super color DNA challenged" AND IT'S STARTING TO MAKE SENSE...

LOVE the coin explanation!!!

Thanks....

HH

[Derby Lyn]

It is actually a filly I am looking at, I do not own her. Her foal pics make her look a seal brown, owner says she is shedding out darker. Dam is a chestnut and sire is a black.

[xfactor fan]

You might want to trace the family tree of the chestnut and see if there are any browns lurking about.

Depending on where the color testing was done, they might not make a distinction between Regular Bay and Wild Bay. They may also lump black and brown together.

So a EE AA, or EE Aa horse could be bay, or wild bay

and a EE aa horse could be black or brown.

[accphotography]

and a EE aa horse could be black or brown.

I think you misspoke here. A brown will ALWAYS test E_ A_. If a horse tests E_ aa it will ALWAYS be black (even if it fades and looks orange it's still black).

[xfactor fan]

Ok,

Brown horse will test as A.

So that rules out brown as a possibility.

Is there still only one place that does testing for brown? Haven't followed the ins and outs of testing for a number of years.

[accphotography]

Until he publishes his findings, yes.

[xfactor fan]

So is the current theory about brown is that it is not Agouti itself but a modifier that lives close to Agouti? Or has that changed?

The only certain thing about genetics is that what we know as fact today, may not be true tomorrow.

Thanks. And thanks for catching my mistake, should know better than to work from memory first thing in the morning.

[accphotography]

He actually claims it IS another allele of agouti itself.