Bays homozygous for black??

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ohmt

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Hey everybody! Sorry if this is a really stupid question. I've really been studying genetics the last couple of years and thought I sorta got most things dealing with color. I just learned about bays last year and what I had learned was that bays have one black and one red gene and also have the agouti gene which causes the minimal amount of black on the horse. I though that even if a horse had the agouti gene and then two black genes they had to be black because there was no red so the black didn't have another color to minimize it's own. THEN I went to a well know horse farm's website and they had posted that their horses were genetically bay but were homozygous for black. I had seen this last week and at first thought that I was just wrong about it and was going to keep it to myself
but it's really been bothering me and I'd really like to know! So if anybody could please explain this to me I'd really appreciate it!! Also, if I'm completely wrong about the whole BAY theory then could you please explain that to me as well.

Thanks in advance for the info!
 

SunQuest

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Actually bays can be homozygous for black. Now the augoti gene ONLY shows up on a black horse. It doesn't matter if the horse has a red gene or not. Augoti is a color modifier and modifies ONLY the black gene, so it changes the black coat color to red leaving just the black points on the horse. So in short, the horse doesn't need a red gene to be a bay and look like a bay.

So yep, a bay can be homozygous for black.
 
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~Palomino~

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Hi, not a stupid question, not everyone knows everything:) Bays can be homozygous for black, that means they got a black gene from each parent, and an agouti from one of them, if a bay is herterosygous, meaning it has a black and red gene, then it will look no diferent that a homozgyous bay, and the black donimates red, so if a horse is heterozygous, its black based forsure, so a homozygous bay just has 2 copies of the black instead of just 1!

-Gage-
 

ohmt

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Thank you so much! I've really never read that anywhere and I think because bays look red and black I just kinda figured they had a red gene and a black one and then read about agouti last year and kinda put it together. Thanks so much again I really appreciated it!
 

chandab

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Yes a bay horse can be homozygous for black. The bay gene (agouti) is a color modifier which only works on black; it restricts black to the points (mane, tail and legs).

The bay stallion in my avatar happens to have a black and a red gene (had him DNA color tested); and in addition he is homozygous for bay, so he will always pass his bay gene onto his foals (even his red-based foals will carry a bay gene).
 

chandab

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~Palomino~ said:
so a homozygous bay just has 2 copies of the black instead of just 1!
-Gage-

463322[/snapback]

Not so... Agouti is a gene modifier and completely separate from the base color, so has nothing to do with whether the horse has one black gene or two black genes. But, a horse can be homozygous for bay, the stallion in my avatar is homozygous bay with one black and one red plus two agouti genes.
 

ohmt

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Okay another question!!


You're bay stallion with the black gene and the red gene....he is a homozygous bay and can only produce bay? I'm a little confused now. What if he was bred to a solid sorrel and then himself passed on the red gene. If bay effects the black only then even if the horse has the agouti gene, how could it be a bay??

Thanks!!
 

~Palomino~

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chandab said:
~Palomino~ said:
so a homozygous bay just has 2 copies of the black instead of just 1!
-Gage-

463322[/snapback]

Not so... Agouti is a gene modifier and completely separate from the base color, so has nothing to do with whether the horse has one black gene or two black genes. But, a horse can be homozygous for bay, the stallion in my avatar is homozygous bay with one black and one red plus two agouti genes.

463326[/snapback]

sorry, I didnt mean bay, When I said homozgyous, I was meaning homozygous for black!!

But it was totally my fault, cause I made it sound like I said homozygous bay, but when I said homozygous I was meaning for black, not agouti

omht, if a horse is homozygous for agouiti, it will put all agouti in his foals, and if they are black based, he will forsure have a bay, and if the cream gene was added a buckskin, but on his red based foals, he could have a sorrel, that has the agouti, and not know it, and it wouldnt look like it, but it would HAVE to be, cause he has to give a agouti to everyone of his offsping!

-Gage-
 
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chandab

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ohmt said:
Okay another question!! 
      You're bay stallion with the black gene and the red gene....he is a homozygous bay and can only produce bay? I'm a little confused now. What if he was bred to a solid sorrel and then himself passed on the red gene. If bay effects the black only then even if the horse has the agouti gene, how could it be a bay??

    Thanks!!

463327[/snapback]

If he is bred to a red mare and passes his red gene, then the foal would be red, but carry the bay gene (it just wouldn't show on the red foal). But, if you were to then breed that foal to a homozygous black (no red or bay gene), the resulting foal could be bay. One black gene, one red gene and the chance of getting the one bay gene.

Totally confused, yet? Aren't genetics fun?
 
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SunQuest

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The base color genes are different than the modification genes. There are 2 base color genes in every horse at the extension locus. They are symbolized by the letters "E" (for black) or "e" (for red)

There are only the 3 possibilities for base color in all horses. They are:

EE - Black horse that is homozygous for Black (will always pass on the black gene)

Ee - Black horse that is heterozygous for Black (50% chance of passing on a black gene)

ee - Red horse that is homozygous for Red (0% chance of passing on black)

Now, everything else just modifies or dilutes the above genes.

So a bay is a horse that genetically has a black base color which could have one or two black genes, and when you add agouti, it modifies the coat color to bay. Now a bay can also be homozygous for Agouti meaning that it will pass on the augoti gene to all foals. But the augoti gene will only show up on a black based horse. So you would not see the agouti gene if a horse is red based, but will ALWAYS see it if the horse is black based.
 

Minimor

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Amanda, just to make it more clear, Chanda is using the term "bay" in place of "agouti"--her stallion is homozygous for agouti, but not for black, so as she just said, he will always pass on the agouti to his foals, though will possibly be red based & not show that they carry agouti.
 

ohmt

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Okay thanks so much!

I actually LOVE genetics and yes they are quite confusing but so much fun at the same time! I've got most of my horses all figured out as far as genes go although I might have to check back with my bays
and I have a couple more that I'm waiting for dna tests on just to be sure. I do have ONE mare that I am totally frustrated about though. I have no idea what color she is!! hhaha. I know she is a dun for sure I just don't know what kind and I am VERY familiar with duns and am pretty confident when identifying one. I call this one a blonde dun (i totally made that up!
) because she really looks like a blonde but she has a dorsel stripe and a slightly darker head and slightly darker lower legs along with the zebra stripes. She also has almost what looks like lacing over her dorsel stripe...very unusual and the rest of her is creamy colored. Her sire looked a lot like her only a little darker and her dam was a red roan (i don't think she was a true red roan but had the white and yellow hairs mixed in-didn't have the darker head and lower legs and didn't have extensive white). So now that I've got the whole BAY thing i was wondering if I may ask if any of you have a mare colored like mine? I can get pictures of her if needed but I'd need to go find them and download (pain!!).
 

ohmt

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I'm going to put a link for pictures on another post
 

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