HOMOZYOGOUS Colors

[Mona]

I have a mare that I had color tested. On the results, it showed Red Factor - Homozygous Red (ee)

Does homozygous red work differently than other homozygous colors and patterns? For example...

A - I have a horse that is homozygous for tobiano...this means she has 2 copies of tobiano...one from each parent. This mare will ALWAYS reproduce the tobiano pattern in her foals.

B - I have a horse that is homozygous for black...this means she has 2 copies of black...one from each parent. This mare will ALWAYS reproduce the color BLACK in her foals.

C - I have a horse that is LWO, which is homozygous for Lethal White...this means she has 2 copies of the LWO gene...one from each parent. Because this pattern is lethal in it's homozygous state, this horse WILL die soon after birth.

D - I have a horse that is said to be homozygous for appaloosa(sno cap and few spot)...This to my knowledge has never been proven gentically, but I am using it as it is claimed to work in the same manner. This means she has 2 copies of the appaoolosa pattern...one from each parent. ALL foals will exhibit some form of appaloosa pattern and/or characteristics.

OK, so here's the thing...if red can be found in a homozygous form, and black can be found in it's homozygous form, what happens to the resulting foal born from a red homozygous and black homozygous pairing?

I am assuming that homozygous red works differently then the other homozygous traits?? This one really confuses me!!

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[tracyCCF]

HOMOZYGOUS BLACK EXPLAINED:

Black and Red are the two basic pigment colors of the horse. Black is dominant. Red is recessive. The Black and Red pigment genes or the "E" Genes are symbolized as follows:

BLACK (DOMINANT) :

EE - HOMOZYGOUS BLACK

Ee - HETEROZYGOUS BLACK

RED (RECESSIVE) :

ee - HOMOZYGOUS RED

Each horse possesses one pair of "E" (Extension) genes or, basic pigment color genes. The offspring that result from the mating of two horses inherits one basic pigment color gene from each parent. Currently there is a DNA-based test called the Red Factor Test, which will determine which genes are present. See the VGL-UC DAVIS RED FACTOR TEST for additional information.

A Homozygous Black (EE) can only pass on the dominant "E" black gene, while the Heterozygous Black (Ee) is able to pass on either the dominant black gene "E" or the recessive red gene "e". A horse must inherit the recessive "e" gene from each parent to be red. Therefore, it is genetically impossible for a Homozygous Black to produce a red foal since there is no recessive red "e" gene to pass on.

 

[Becky]

I'm sure someone can explain it better than I can, but here goes!

A red horse is homozygous for red but in recessive form. (ee). A black horse is either homogygous for black (EE) or heterozygous for black (Ee). Black is dominant over red. So unless a horse inherits red from both parents the resulting foal will be black based. Clear as mud???

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I never bother to have a red horse tested as they will ALWAYS be homozygous recessive for red and will always pass a red gene on to their offspring.

 

[Mona]

Thanks Tracy and Becky for that explanation. Now here is my next question...in order for a horse to be homozygous red, wouldn't they have to have both red parents? Or do the parents only have to each CARRY a copy of red and pass it along that way?

 

[justjinx]

Each parent would only have to CARRY red, the foal would then have 1/4 chance of being ee, or homozygous red.

jennifer :saludando:

 

[Mona]

Thanks Jennifer for the info. The reason I am asking, is because I have a sorrel pinto mare. Her sire is a bay pinto, her dam is a silver chestnut pinto. I had her color tested and she is ee - homozygous red. I wondered how on earth she could be homozygous for red, since her sire(and maybe even her dam) is obviously black-based! She was PQ so I know those ARE her parents, so I began to wonder if the testing for colors was incorrect. Thanks everyone!

 

[Lauralee]

Homozygous red (ee) doesn't really mean that it carries RED genes. It means that it LACKS the black gene (Ee or EE) which colors the coat black. ee is a LACK OF black being present.

 

[ThreeCFarm]

Mona, it is like with pinto. Does it take two homozygous tobiano parents to produce a homozygous tobiano foal? Nope! And a black horse can carry a red gene, as long as they aren't homozygous for black. I have a black based mare (silver dapple) that also carries a red gene as she has had red foals, and I have a black based stallion (bay) that is homozygous for black and will NEVER produce a red foal.

And remember, just because a horse is homozygous for black, doesn't mean they will always have black foals, just black-based foals such as bay, black, buckskin, etc, just depending on the genes involved. However, some horses are also homozygous for agouti, which in combination with homozygous black, would mean the horse would only have bays, buckskins, etc, again depending on the genes involved, but would never have a solid black.

 

[rabbitsfizz]

If the horse is Red- ie Sorrel or Sorrel Pinto etc then it is automatically H/Z for Red.

If it is Black/ Black based it can be H/Z or Heterozygous for Black.

If it is heterozygous then one half of it's genes must be Red as there is only Red and Black.

If it is H/Z, then both sets of genes are Black.

Since your mare is a Sorrel Pinto she has to be H/Z for Red.

If she had anything els going on it would show.

 

[Tammie-C_Spots]

Simply- the black is dominant over red so if you have a homozygous black to homozygous red you'll get a black foal with recessive red.

Tammie

D - I have a horse that is said to be homozygous for appaloosa(sno cap and few spot)...This to my knowledge has never been proven gentically, but I am using it as it is claimed to work in the same manner. This means she has 2 copies of the appaoolosa pattern...one from each parent. ALL foals will exhibit some form of appaloosa pattern and/or characteristics

LP (Leopard complex) is a incomplete dominant gene. This means that other genes the horse is carrying will effect how the horse looks so it's not simple like black/red.

Thanks Tracy and Becky for that explanation. Now here is my next question...in order for a horse to be homozygous red, wouldn't they have to have both red parents? Or do the parents only have to each CARRY a copy of red and pass it along that way?

all red horses are homozygous red (ee). Horses can carry a red gene recessively. Quite often black horses carry red recessively. Black is dominant so the horse "looks" black even if they carry red. People are often surprised to see a red foal from two blacks but if both sire and dam carry red recessively the foal may inherit both the recessive reds from the parents hence the red foal. If the foal were to inherit one black and one red then the foal would look black but carry red recessively.

Tammie

her dam is a silver chestnut pinto- I wondered how on earth she could be homozygous for red, since her sire(and maybe even her dam) is obviously black-based!

Her dam is red based. A chestnut is of the red family. The silver is considered a dilution to any other color.

Tammie