I think saying "If a horse is recessive (heterozygous) for agouti, they would look just like a horse that is dominant (homozygous) for agouti. " is very, very confusing.
“recessive for Agouti” really should be aa - nothing to modify black, recessive.
Likewise, “dominant for Agouti” should really be A? - at least one form of Agouti that would dominate the modification of black pigment.
Agouti in the A, At, or A+ form is a dominant form, and does not have to be homozygous to affect the black pigment. It’s still dominant in a red horse, it’s just there’s nothing to dominate
Sounds like the advertiser means the horse will always produce black points (bay) horses because he is homozygous black and homozygous agouti. Better ways of describing it of course but that’s how I would have understood the advert.
I don’t know much about color but have owned a Trakehner stallion that was EE and black. An EE horse cannot produce chestnuts, but doesn’t that also mean that all his offspring will have black points??
I admire you folks that really understand all the permutations of this color stuff!
Right, an EE horse cannot produce anything red-based. He will pass E 100% of the time, and since E is dominant over e, any Ee horse will be black-based as well, and of course any EE horse is too
Whether they will all have “black points” really depends on what you think that means
Black horses would, technically, have black points, yes - everything (that isn’t faded) is black. But USUALLY, “black points” refers to bays/browns - reddish/brownish body with black points.
Now, if someone is using “black points” to mean “not red-based”, then yes, the EE horse IS “homozygous for black points, cannot produce a red-based color”
I admire you folks that really understand all the permutations of this color stuff!
It’s actually really, really simple once you understand the very basics of Extension and Agouti, and then understand that all other modifiers have a dominant form
[QUOTE=JB;6149997]
I think saying "If a horse is recessive (heterozygous) for agouti, they would look just like a horse that is dominant (homozygous) for agouti. " is very, very confusing.
“recessive for Agouti” really should be aa - nothing to modify black, recessive.
Likewise, “dominant for Agouti” should really be A? - at least one form of Agouti that would dominate the modification of black pigment.
Agouti in the A, At, or A+ form is a dominant form, and does not have to be homozygous to affect the black pigment. It’s still dominant in a red horse, it’s just there’s nothing to dominate :)[/QUOTE]
good point… I was thinking she meant Aa … but I guess aa would work. Though the example was buckskins, which are always at least Aa so aren’t (using your definition) recessive for agouti, so I though she meant heterozygous… so who knows.
The horse may be such a dark bay that he looks black. Just ask for the genetic markers. Only AA is homogyzous for black points. Aa would make him heterozygous for the agouti modifier. A true black horse will be aa.
I think it may be an error in the way the info was written…their info says hes HZ for black points but goes on to say he can’t sire red foals…which would mean he’e “EE”…perhaps they don’t understand the use of the word “points” to refer to legs/mane/tail or perhaps they mean that all foals will be black based so that even if the mare contributes “A” or “At” or either of those along with cream “Cr”) the mane/tail/legs would still be black.
I don’t mean to be thick about this, but I thought that an EE horse will always produce black or bay and that to me always implies black points (as in mane, tail, and socks).
I always thought that to have black points some part of the horse needed not to be black. lol I think of having black points as another way of saying bay or buckskin (that isn’t wild bay, with short brown socks).
siegi - You are right, EE horses cannot produce chestnut foals. The term ‘black points’ refers to black legs, mane, and tail, like on a bay or brown. It’s not usually used to describe black horses (because they are black all over).
Of course you could have the scenario whereby a homozygous black stallion were bred to a silver mare and if she passed on the silver gene you could end up with a foal with platinum mane & tail, technically the base colour of the points would be black but wouldn’t have the appearance of black.
In addition if bred to a tobiano mare it’s possible that all four legs could be white with no black points on the limbs. The mane and tail could also be completely white with no black hair either.
So no a homozygous black will not guarantee black points 100% of the time.
Best just to stick with the simplest of explanations which is a homozygous black stallion cannot sire chestnut foals.
[QUOTE=siegi b.;6150441]
I don’t mean to be thick about this, but I thought that an EE horse will always produce black or bay and that to me always implies black points (as in mane, tail, and socks).
What am I not getting?[/QUOTE]
EE will indeed always produce something black-based - black, bay, brown, buckskin, bay or brown dun, smoky brown, smoky black, etc.
BUT, he could also be responsible for a Silver, as he can be EE and be Silver, and if the foal expressed Silver well, the mane and tail can be, well, silver LOL White/silvery, whatever you wish to call it, at its maximally expressed form. The legs of those horses can also be “diluted”, particularly if talking about a Bay Silver. there are many, many silver bays registered as and called chestnut because they truly do look chestnut - no black anywhere - to the untrained eye or at first glance.
[QUOTE=grayarabpony;6150459]
I always thought that to have black points some part of the horse needed not to be black. lol I think of having black points as another way of saying bay or buckskin (that isn’t wild bay, with short brown socks).[/QUOTE]
I think 99% of the time I hear “homozygous for black points” they are talking about the horse being AA, so yes, that’s what I think of when I hear someone say that.
Unfortunately, it’s really a bad phrase to use because it’s really not clear at all what is meant.
[QUOTE=JB;6150701]
I think 99% of the time I hear “homozygous for black points” they are talking about the horse being AA, so yes, that’s what I think of when I hear someone say that.
Unfortunately, it’s really a bad phrase to use because it’s really not clear at all what is meant.[/QUOTE]
I would have thought so too JB, but wouldnt use that term either because we also have the scenario of a homozygous agouti horse carrying red… in which case that doesn’t guarantee anything either and again with the silvers and tobianos the same scenario can crop up.
Even if a horse is homozygous black and homozygous agouti the latter also applies, so this term should never be used as a blanket statement regardless.
