A few genetics questions? - Page 2 - The Horse Forum
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post #11 of 18 Old 12-06-2012, 05:25 PM
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Originally Posted by Kilokitty View Post
..Woops. Lol, I meant heterozygous as in only one parent was a chestnut, the other was palomino.

Homozygous as both parents were bay. I didn't know horse genetics were so confusing! What exactly is this "agouti" gene?
It can be confusing.

I will be using black for this example:
Homozygous means both alleles are the same EE (homozygous dominant horse = black) or ee (homozygous recessive horse = chestnut). Heterozygous means the alleles are different Ee (heterozygous horse = black carrying chestnut). Those words don't mean that a horse's parents were the same or different colors, it describes individual color genes.

Agouti is the gene responsible for turning black horses into bays or browns. A bay horse (brown tone with black mane, tail, legs) is actually a black horse with the agouti gene. This gene (A) says "hey black color, you can only be on these parts of the body" so black is restricted to the points and voila! Bay horse. Brown is also a type of agouti (At) they can appear to look bay during the summer, but in the winter they get darker in color and they get mealy/lighter around the muzzle, flanks, and other soft body areas.

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post #12 of 18 Old 12-07-2012, 12:17 AM
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Wow I love doing genetics and genotypes but this just threw a bone in my thinking cap..

Ill just sit back and watch LOL
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post #13 of 18 Old 12-07-2012, 01:20 AM
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Okay, now that we've had some clarification, I will attempt again but more or less disregarding the homozygous/heterozygous parts.

Homozygous black + Heterozygous chestnut ( Chestnut + palomino) = ________? If your black is actually homozygous black, your options are black, bay, or brown. The agouti gene mentioned above that restricts black into bay, brown, or wild bay can be carried by chestnuts but you wouldn't know without testing because chestnuts are homozygous red and have no black to restrict.

If you have a heterozygous black + chestnut, you'll get black, bay, brown, or chestnut.


Heterozygous grey ( Gray and bay)+ Heterozygous red dun ( Dun + Chestnut)= ________? The grey would be heterozygous here because it only has one gray parent. However, I do not know the grey horse's base color (as every grey is a "normal" color underneath, but grey covers it). So I can't answer that, but I can tell you it will have a 50% of being grey.

Homozygous bay+ __________ = Palomino? Well, the bay couldn't be homozygous black or palomino wouldn't be possible as it is red-based. It would also have to be something with cream and heterozygous black, so smoky black, smoky cream, buckskin, perlino, palomino, or cremello.

Homozygous chestnut tobiano+ ________ = Heterozygous bay overo? I'll consider the tobiano heterozygous even though I think you mentioned that you meant to put tobiano instead of overo. I'll also just go with the word overo rather than the individual patterns. Your color options would be really any black based color that is heterozygous for all of its other genes (ie, buckskin is heterozygous for cream, a blue roan that only has one copy of Roan, a dun with only one copy of dun, et cetera) plus one or more overo genes.
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post #14 of 18 Old 12-07-2012, 02:29 AM
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Quote:
Originally Posted by Poseidon View Post
Okay, now that we've had some clarification, I will attempt again but more or less disregarding the homozygous/heterozygous parts.

Homozygous black + Heterozygous chestnut ( Chestnut + palomino) = ________? If your black is actually homozygous black, your options are black, bay, or brown. The agouti gene mentioned above that restricts black into bay, brown, or wild bay can be carried by chestnuts but you wouldn't know without testing because chestnuts are homozygous red and have no black to restrict.

If you have a heterozygous black + chestnut, you'll get black, bay, brown, or chestnut.


Heterozygous grey ( Gray and bay)+ Heterozygous red dun ( Dun + Chestnut)= ________? The grey would be heterozygous here because it only has one gray parent. However, I do not know the grey horse's base color (as every grey is a "normal" color underneath, but grey covers it). So I can't answer that, but I can tell you it will have a 50% of being grey.

Homozygous bay+ __________ = Palomino? Well, the bay couldn't be homozygous black or palomino wouldn't be possible as it is red-based. It would also have to be something with cream and heterozygous black, so smoky black, smoky cream, buckskin, perlino, palomino, or cremello.

Homozygous chestnut tobiano+ ________ = Heterozygous bay overo? I'll consider the tobiano heterozygous even though I think you mentioned that you meant to put tobiano instead of overo. I'll also just go with the word overo rather than the individual patterns. Your color options would be really any black based color that is heterozygous for all of its other genes (ie, buckskin is heterozygous for cream, a blue roan that only has one copy of Roan, a dun with only one copy of dun, et cetera) plus one or more overo genes.
Your answer with Heterozygous grey ( Gray and bay) + Heterozygous red dun, wouldn't (Gray and bay) mean its base coat is bay?

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post #15 of 18 Old 12-07-2012, 02:55 AM
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Originally Posted by Nokotaheaven View Post
Your answer with Heterozygous grey ( Gray and bay) + Heterozygous red dun, wouldn't (Gray and bay) mean its base coat is bay?
No, the OP clarified that what they meant by the parentheses were what color the parents were of that horse. A grey and a bay produced another grey, but that doesn't tell me what the grey's base color is, just that it is heterozygous for grey.
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post #16 of 18 Old 12-07-2012, 03:07 AM
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Originally Posted by Poseidon View Post
No, the OP clarified that what they meant by the parentheses were what color the parents were of that horse. A grey and a bay produced another grey, but that doesn't tell me what the grey's base color is, just that it is heterozygous for grey.
oh lol, oops my bad

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post #17 of 18 Old 12-07-2012, 09:58 PM Thread Starter
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I suppose the grey's base can be bay, also? Makes the most sense to me.
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post #18 of 18 Old 12-07-2012, 11:44 PM
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Bah. I typed this out and accidentally closed it.

The base of the gray could be bay, but since the gray parent of it would also have an unknown base color and we didn't see the horse born, etc, we don't know.

For the sake of this thread: bay-based (assuming heterozygous for agouti) gray + red dun = chestnut, bay, black, red dun, bay dun, grullo. And then a 50% of staying one of those colors and 50% of graying.
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