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Horses
Apr 5, 2006 1:27:32 GMT -5
Post by Ryan Wunsch on Apr 5, 2006 1:27:32 GMT -5
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Horses
Apr 5, 2006 9:59:34 GMT -5
Post by vanderkm on Apr 5, 2006 9:59:34 GMT -5
OMG - love that buckskin!! Some days I miss living in the country. The appaloosas are lovely too. Any babies this spring?
mary v.
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Horses
Apr 5, 2006 10:31:27 GMT -5
Post by Ryan on Apr 5, 2006 10:31:27 GMT -5
Nice pics as always Ryan! Even though I don't know a thing about them I've always wanted a horse and will probably start thinking about it in a couple years or so.
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alex
Active Member
Posts: 91
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Horses
Apr 5, 2006 22:39:52 GMT -5
Post by alex on Apr 5, 2006 22:39:52 GMT -5
We had two lethal whites born at the college this summer incidental to a research project. One mare had one small white marking, much like a scar, that was the only indication that she was a paint. They were allowed to live long enough to get some footage for teaching purposes, and then they were euthanised. Congenital aganglionosis is not a pretty way to die, and it is uniformly fatal. Basically the myenteric nervous system (which is equal in size to the spinal cord) doesn't develop, so there's no capacity to move food through the gut and digest it. There's no such thing as a white horse I suspect your paint is a paint without markings - for some reason, paints and appaloosas can have a purebred animal who displays no pattern, rather than homozygous lethal white because you simply cannot live without a functional GIT. Personally, I like the colour of the appie roan at the bottom the best.
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Horses
Apr 5, 2006 22:49:52 GMT -5
Post by Ryan Wunsch on Apr 5, 2006 22:49:52 GMT -5
We had two lethal whites born at the college this summer incidental to a research project. One mare had one small white marking, much like a scar, that was the only indication that she was a paint. Horses don't have to carry the paint gene to carry the lethal white gene. Quarterhorses can produce a lethal white foal if each carries it (and they can). All 4 types of paint genes (on differentl loci), as well as non paints (breeding stock), can carry the recessive lethal white gene. There is no such thing as an albino horse. There is however a white gene (co-dominant) that produces white horses. Our horse is all white in color, but not albino, and she is not a "white" genetically. But there are white horses, not just not albinos. Ours likely is an all white sabino, they are kind of rare, but not impossible. She may not carry the lethal white recessive gene, I am going to have her (and my stud) tested for the gene. Thanks for the horse genetics discussion, I love horse genetics! Ryan
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Horses
Apr 5, 2006 23:02:28 GMT -5
Post by Ryan Wunsch on Apr 5, 2006 23:02:28 GMT -5
There are homozygous paints (tobiano's, frame overo's, splash overo's and sabino's), that are not lethal white. It used to be thought lethal white followed frame overo's, but not all frame overo's carry it. Because there are some overo's in the parentage of "breeding stock" paints, and some quarterhorses - solid colored horses can carry lethatl white (even quarterhorses, a different breed)
Some pure white paints are homozygous for one of the 4 paint genes, or even carry all 4 in heterozygous form, and the white totally covers the colors (except the eyes, but in many cases the eyes are blue)
Ryan
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alex
Active Member
Posts: 91
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Horses
Apr 6, 2006 7:06:28 GMT -5
Post by alex on Apr 6, 2006 7:06:28 GMT -5
They're not technically called white though. According to the insane horse people who attempt to teach me to care for horses, they're grey. You could still combine dilute with grey to make it paler, but it's still called grey.
I have issues with even naming colours in horses. Dun is not considered a foundation colour even though it's wildtype, which drives me nuts.
I have no idea what a sabino even is, so okay. Lethal white isn't equivalent in to that paint gene, but it's so closely associated with it that the incidence is much, much, much lower in regular QH population and they're so inbred in the serious lines there's a lot of other scary things, like some of the muscle disorders. And see, the solid coloured quarter horses are what I mean - when you get a paint that is a solid colour. They're homozygous with no outward expression of it, or the one at school who just looks like she has a scar. We have some of the appies kicking around the school, they're doing a research project on the fact that a lot of them are nearly blind, and they want to see if it's in purebred appaloosas who just don't have spots
And there's always the chance someone snuck into her mother's pen. My friend had a mini pony stud sneak off the neighbour's property and impregnate a percheron x, if that gives you an idea how determined he was
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Horses
Apr 6, 2006 7:56:54 GMT -5
Post by kaley on Apr 6, 2006 7:56:54 GMT -5
They're not technically called white though. According to the insane horse people who attempt to teach me to care for horses, they're grey. You could still combine dilute with grey to make it paler, but it's still called grey. Sorry - gotta jump in here - an "all white paint" would be about the only colour you could actually call white. That horse is NOT grey!! It's true that most horses that people would call white just by looking at them are properly called grey, but an extreme spotting phenotype like Ryan's mare would properly be called a white horse. Kaley
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Horses
Apr 6, 2006 8:07:23 GMT -5
Post by kaley on Apr 6, 2006 8:07:23 GMT -5
Horses don't have to carry the paint gene to carry the lethal white gene. Quarterhorses can produce a lethal white foal if each carries it (and they can). All 4 types of paint genes (on differentl loci), as well as non paints (breeding stock), can carry the recessive lethal white gene. Ryan - can you point me to some resources explaining that statement? My understanding of lethal white was that it so closely linked with overo that some people are starting to call for the presence of the lethal white gene as the difinitive test for the pattern overo, and that non overo paints with the gene are likely really mis-labelled pattern wise...And also, that the only horses found so far with the lethal white gene had an overo parent somewhere in their recent pedigree...So if you could point me to a paper or something, that would be cool...An undergrad in our department just did a lit. review thesis about Overo lethal white, so I'll try to get my hands on that and sort this out in my brian. I think you may be a little mixed up... kaley
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Horses
Apr 6, 2006 9:34:03 GMT -5
Post by Ryan Wunsch on Apr 6, 2006 9:34:03 GMT -5
Yes they are. The Grey gene is different than dominant white, Grey makes the horse look white with age. I'm not talking about that, I'm talking abut the white gene, where the baby is born white (but not albino) Here is more info I quickly found. There is a lot more information on line if you are interested. en.wikipedia.org/wiki/Gray_(horse)"True white horses, those that carry the Dominant White gene, are extremely rare. See a description of the Dominant White gene and a photo at the UC Davis Veterinary Genetics Laboratory. The difference between a gray and a white horse is the skin color: gray horses have black skin, white horses have pink skin. Some gray horses may have a pink nose (which, if they had a dark color coat, would had been the place where they had a white marking on their face). White horses always have a pure white coat, with absolutely no other color hair. They are born white (unlike a gray, which is born dark coated) and stay that color the rest of their life." www.vgl.ucdavis.edu/~lvmillon/coatcolor/coatclr3.html#fig1aDifferences between G and W genes www.vgl.ucdavis.edu/~lvmillon/coatcolor/coatclr3.html#genew"This gene and the gene G, to be discussed in the next section, will be presented first because they have alleles whose actions can obscure the actions of the other coat color genes. If either allele W of the W gene or allele G of the G gene is present in the hereditary material of a horse, it is difficult or impossible to determine its other coat color genes by superficial examination, so the colors these alleles produce can be simply dealt with at the onset of this discussion. In the presence of the dominant allele W, a horse from birth will typically lack pigment in skin and hair. The skin is pink, the eyes brown (sometimes blue), and the hair white. Such a horse is termed white (Fig. 1A). Sometimes such a horse is called albino. -------------------------- Kaley... There have been a lot of new findings regarding horse genetics, It's not suprising that all the new information and studies are not widely circulated. Maybe you should look at some newer studies and information regarding some of this.... I'm a horse genetics nut though, and keep right on top of the new findings as much as I can. There is an egroup with the members of the UC Davis Veterinary Genetics Laborator, if anyone would care to join it, I could find the link to it. A lot of the information on line is still old information, and studies are still being done. People used to use the term frame overo and lethal white interchangebly, but research seems to be finding that not all frame overos cary lethal white and not all lethal whites are frame overos (i think since the genes are on different loci, so a frame overo bred to a breeding stock [non lethal white carrier] should have a 50% chance of not passing on the lethal white gene) that is if the lethal white gene does not follow frame overo which is the new theory (of the day). I do think it is possible that like you said, many of the solid horses that are carriers might be minimally expressed paints, but the research is on going, and at last I checked that group they though the recessive lethal white gene was independent, and was found in horses that did not carry any of the paint genes at all. en.wikipedia.org/wiki/Lethal_white_syndrome"Lethal white syndrome first appeared among overos, and so was called overo lethal white syndrome (OLWS), and it is a widespread misunderstanding that all overos carry it. In reality, research by the University of Minnesota has shown that LWS is not directly tied to the overo phenotype: not all overos carry it, and in fact some tobianos and even a small number of crop-out quarter horses and other breeds carry it as well. This misunderstanding is perpetuated by older theories predating the blood test, such as those of UC Davis's Laurie Fio, which claim that LWS results from a homozygous frame overo gene. [1]" www.pubmedcentral.nih.gov/articlerender.fcgi?artid=339559"Foal with Overo lethal white syndrome born to a registered quarter horse mare" www.apha.com/breed/lethalwhites03.html"Concurrently, we are testing Paints from all over the country to determine the association of the Lethal allele with coat color. While the results are not yet final, it appears that all overo horses are not the same, at least for this gene. Overos can carry either (N/N) or (N/L)." www.vgl.ucdavis.edu/horse/lethalwo.htm"The gene appears to be associated with horses often characterized as "frame-overos" in Paints and Thoroughbreds, but is also present in some tobiano/overos, some solid-colored (breeding stock Paint) offspring from overo matings, some tobianos and Quarter Horses without obvious evidence of the overo pattern." www.netpets.org/horses/healthspa/lethal.html"The defective gene has been found in American Paint Horses, American Miniature Horses, Half-Arabians, Thoroughbreds, and cropout Quarter Horses (foals born to registered Quarter Horse parents that have too much white to qualify for registration with the American Quarter Horse Association). " Here is a link to an older study 1997 (with old information and old theories...about all frame overo's being lethal white), but mentions newer study going to be done on Lethal Whites www.apha.com/breed/lethalwhites01.html"Recently, lethal white syndrome has also been examined from a genetic standpoint. In July of 1996, a team of researchers at the University of Minnesota sent the APHA a comprehensive proposal for a grant to describe the inheritance of lethal white syndrome and to locate the gene responsible. In November, the APHA Executive Committee approved the $7,650 grant, and the project is now under way. " Some other interesting (but with possible older info) links www.netpets.com/horses/healthspa/lethal.htmlwww.vgl.ucdavis.edu/~lvmillon/--------------------------- I can not find where I read about the existence of homozygous frame overo horses, or heterozygous frame overos that do not carry the lethal white gene. Possibly it was when I was a member of that newsgroup, I might look it up and join up again. They are still learning however, a lot more information is going to be coming. I think horse genetics are really exciting and am glad to have people to discuss them with. Kaley, since you are taking genetics it might be worth getting into contact with the 2 universities that are doing the genetic testing and research. They probably have new studies published in journals that are not on line, and all of this "new" info might again be "old info" Ryan Fixed up links that weren't working, now they are
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Horses
Apr 6, 2006 9:56:04 GMT -5
Post by Ryan Wunsch on Apr 6, 2006 9:56:04 GMT -5
There is more information about registered quarterhorses carrying lethal white.
I think the reason that some do, are that some "solid" paint horses are allowed in the registry, and these horses could carry a copy of the gene. These horses could also technically be minimally marked overo's I think.
Now get ready for this.... The AQHA changed their white rules, and are allowing cropouts to be registered. Most cropouts are Sabino patterned, but now there are registered quarterhorses that look just like paint horses, and have a lot of white splashy paint markings. I'd like to find a cropout stud that could be registerred as a quarterhorse, I predict that "painted quarterhorses" are going to be very popular in the future.
If the Pinto club wanted to get a step up on the paint club, they should not allow any paints that test positive as carriers of lethal white, in the breeding program, in my opinion.
In any case, there is still a lot of confusion about the Lethal White gene, and It will be years before they sort everything out. Not too long ago, Frame Overo was thought to be recessive itself (hence so many frame x frame breedings) and that might be the reason there are so many lethal white genes in Frame Overos.
Or, maybe all frame overos do carry the lethal white gene... and the frame overo's they've tested that don't have lethal white, aren't actually "frame overo" but another paint pattern genetically.
Its also possible that the quarterhorses, tobiano's and other paint patterns that are lethal white carriers, also carry frame overo, but it is minimally expressed.
Hopefully more grants will be forthcoming to the people researching lethal white. Also, hopefully tests like the ones that test for tobiano in heterozygous or homozygous form, can be formed for the other 3 paint patterns.
At least there is a lethal white test that horse people can do, and I think it would be responsible to not breed any lethal white carriers. But, if in a few years we find that all frame overo's carry lethal white - it would be a tough choice to discontinue breeding any frame overo's, but maybe a regulation could be put in place so that people only breed frame overo's to solid colored horses, and that all babies are tested for lethal white.
Ryan
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Horses
Apr 6, 2006 10:00:51 GMT -5
Post by kaley on Apr 6, 2006 10:00:51 GMT -5
I'll look through those links when I get this stupid assignment I'm working on done...I'll also try to get hold of that thesis, which should sum things up nicely... (i think since the genes are on different loci, a frame overo bred to a breeding stock (non lethal white carrier) should have a 50% chance of not passing on the lethal white gene. You are little mucked up here though...the 50% chance of passing the gene on only holds if the two genes are inherited independently - two genes (genes are separate loci by definition!) on the same chromosome that are very close together are inhereted together unless their is a recombination event...and the liklyhood of recombination is directly related to how close together the genes are on the chromosome...I believe that these two genes you're talking about are linked - that is they are not inherited independently .... I'll look into it more... kaley
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Horses
Apr 6, 2006 10:09:11 GMT -5
Post by Ryan Wunsch on Apr 6, 2006 10:09:11 GMT -5
You are little mucked up here though...the 50% chance of passing the gene on only holds if the two genes are inherited independently - two genes (genes are separate loci by definition!) on the same chromosome that are very close together are inhereted together unless their is a recombination event...and the liklyhood of recombination is directly related to how close together the genes are on the chromosome...I believe that these two genes you're talking about are linked - that is they are not inherited independently .... Like I said in my long post above, the new research is making them think that the lethal white gene is not linked to overo. I'll see if I can dig up what I read about that specifically, it may have been just speculation by one of the Drs. on that list I was on for a bit, but I'm sure I read something more formal about that theory... I think that without more genetic tests available which test for all 4 paint patterns, it will be hard for them to prove that the lethal is linked or is not linked to the frame overo pattern. They could be mistaking patterns as I mentioned above, when finding "frame overo" horses that are not carriers of lethal white, as they said they have (and if they are basing the existance of a homozygous frame overo on only breeding trials, that is not conclusive proof either). As I also said, maybe all the carriers of lethal white are infact frame overo, but minimally marked in some cases. Some of the things I read were second hand info, maybe the brand new new research has proven a link with lethal white and frame overo. I think I am off to go find and join that group again and see what today's theory is. Ryan
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Horses
Apr 7, 2006 11:32:40 GMT -5
Post by kaley on Apr 7, 2006 11:32:40 GMT -5
Some of the things I read were second hand info, maybe the brand new new research has proven a link with lethal white and frame overo. I think I am off to go find and join that group again and see what today's theory is. Ryan So Ryan...Are you going to tell the nice folks what you found out? ;) Kaley
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Horses
Apr 7, 2006 11:49:47 GMT -5
Post by Ryan Wunsch on Apr 7, 2006 11:49:47 GMT -5
Some of the things I read were second hand info, maybe the brand new new research has proven a link with lethal white and frame overo. I think I am off to go find and join that group again and see what today's theory is. Ryan So Ryan...Are you going to tell the nice folks what you found out? ;) Kaley I have not found out anything "new new" yet, I was thinking that you might be able to get to the bottom of things through your university contacts. I will look for that list and join it and ask, or send an email to the person heading up that study some time this weekend though. What I did say in an email to Kaley was..... But I will say, I think it is too early to form any concrete beleifs yet, the study is still on going. And as you said, everything is "theory"... If you have heard the "theory of the day" feel free to post it, as I said I will make a point of asking the right person the question hopefully over the weekend... I will post my findings on this thread for all who are feverishly keeping up with all the interesting horse genetics discussion... both of us I think :) Ryan
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Horses
Apr 7, 2006 12:59:01 GMT -5
Post by kaley on Apr 7, 2006 12:59:01 GMT -5
Ok fine, I'll shut up about it and quit being a pest! You know I was just fishing for a "Kaley was right post"!? ;D
I am a little hurt that not everyone on the list is on the edge of their seats over this...I mean what could possibly be more important/interesting than horse coat colour genetics, especially to a bunch of reptile people...? ;D
Oh well, back to work...Can you tell that I'm bored?
kaley
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Horses
Apr 7, 2006 17:30:16 GMT -5
Post by Ryan Wunsch on Apr 7, 2006 17:30:16 GMT -5
Ok fine, I'll shut up about it and quit being a pest! You know I was just fishing for a "Kaley was right post"!? ;D kaley Well, you have not provided any proof towards your theory, but I have provided quite a bit resource material supporting the theory I presented, and one that right or wrong is currently being accepted by the horse people who think they are ahead of the game.... But I see that I need to find proof for your theory, so I will track down the person in charge of the study, to find out what the "theory of the day" will be. Your welcome in advance And, if your theory happens to be the current "theory of the day", why did you not know that the accepted theory on the subject had gone through a change? At least I keep up with things, accurate, or inaccurate. So nyah! I will post the full email I receive and any information I am given in my tireless quest for the truth, all alone and by myself. Ryan P.S. Have you ever thought of doing a thesis or some project on horse color and pattern genetics?
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Horses
Apr 7, 2006 19:01:59 GMT -5
Post by kaley on Apr 7, 2006 19:01:59 GMT -5
[quote author=admin board=mammalsbig thread=1144218452 post=1144449016 Well, you have not provided any proof towards your theory, [/quote] I'm working on it - I'm still trying to track down that girl's thesis! We only started this yesterday!! And I DO have proper work to be doing in the meantime! Thanks! I could use the help - as I mentioned, I do have things that I really should be doing at school rather than mucking around with horse stuff! Besides, the more people we have searching for the "right" answer, the more likely we are to find it! Well you've got me there...I only recenlty started paying much attention to this topic...You win! I think that would be cool...someday! I don't really have time for extracuricular research right now...but hopefully by this time next year I will! Kaley
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