Homozygous Roan Lethal? - Page 2 - The Horse Forum
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post #11 of 45 Old 08-20-2012, 09:46 PM
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This is what I found.

the roan gene has been idenified




Roan, along with dominant white, sabino-1 and tobiano have all been mapped to the KIT gene region on Chromosome 3. KIT is a large complex protein involved in many important aspects of metabolism. Some KIT mutations are homozygous lethal, including some of those causing dominant, of which there are more than one, in different horse populations.

As with dominant white there may be more than one roan allele, some may be homozygous lethal, others not.

roan horses
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post #12 of 45 Old 08-20-2012, 09:53 PM
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wut.

That website uses a study from 1979. I think we've made a bit of scientific progress since then.
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post #13 of 45 Old 08-21-2012, 12:37 AM Thread Starter
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What all should I include in the email I send her? Just mention that the information is not correct and provide her the link to UC Davis or? Makes me wonder what else is incorrect that I'm not noticing.
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post #14 of 45 Old 08-21-2012, 04:08 AM
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First of all, I think it's awesome that you identified that piece of information as incorrect, and you definitely should tell her. In my Conservation Biology class my professor knew less about certain topics than I did, mostly because I get very obsessive over certain facts. She also told me I was wrong when I answered a question and I knew I was right beyond any doubt so I had to e-mail her and set her straight. Just goes to show that a PhD helps, but it does not mean everything.

If I were you, I would just explain that the belief that "homozygous roan is lethal" was founded on a paper from the 1970s--they thought that it was lethal because there were fewer roan offspring from roan to roan matings than were expected based on what they knew about genetics at the time. This lead them to conclude that it was lethal to the embryo, but it has actually been shown that it's less straightforward than that. There are living horses which have been shown to be homozygous roan.

Don't know if anyone has posted this link yet: http://www.hancockhorses.com/article-roanQHNews.pdf

It gives some good information on the findings by UC Davis and discusses the "forthcoming" paper. I can't find the paper anywhere, is it just not published yet?
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post #15 of 45 Old 08-21-2012, 06:33 AM
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Don't tell her her info is incorrect. Suggest to her that you are confused by all the information you've been given both by her and what you've read. That way hopefully she won't take offence. She's the one who grades your papers.
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post #16 of 45 Old 08-21-2012, 07:04 AM
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Quote:
Originally Posted by PhelanVelvel View Post
If I were you, I would just explain that the belief that "homozygous roan is lethal" was founded on a paper from the 1970s--they thought that it was lethal because there were fewer roan offspring from roan to roan matings than were expected based on what they knew about genetics at the time. This lead them to conclude that it was lethal to the embryo, but it has actually been shown that it's less straightforward than that. There are living horses which have been shown to be homozygous roan.
I want to elaborate on this because it is a very good point. Roan is a very complex simple dominant lol. It is a mutation of the KIT gene, which automatically makes things complicated. There are currently four KNOWN and TESTABLE mutations of the KIT gene - tobiano, dominant white, roan and sabino 1. This means that only two copies of ANY of these genes can be inherited. So we can assume this horse is heterozygous for both tobiano and roan, and does not have sabino.



The KIT gene is also linked to the extension gene, to the point where they inherit in pairs. If, for example, you had a Ee Toto stud, let's assume the E is linked to the To and the e to the to for this discussion. His foals will inherit either E To or e to, never e To or E to.
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post #17 of 45 Old 08-21-2012, 09:13 AM
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If you can find documentation that the teacher is in error, you should bring it forward. But do it in a nice way. This person is highly educated, and if you come across as arrogant, she will no doubt embarrass you severely. Nobody knows everything. The entire genetic plan of all horses has not been firmly established or proven. She will welcome intelligent discussion. She will hate arrogant crap.

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post #18 of 45 Old 08-21-2012, 09:20 AM
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He's RnRn .. tested.

Looks pretty good for a dead guy, huh?

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post #19 of 45 Old 08-21-2012, 09:51 AM
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Quote:
Originally Posted by Bridgertrot View Post
What all should I include in the email I send her? Just mention that the information is not correct and provide her the link to UC Davis or? Makes me wonder what else is incorrect that I'm not noticing.
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I would include a link to UC Davis - the ackowledged experts on the subject.

Roan

Quote:
Although it has been suggested that Roan is a homozygous lethal, evidence from the Quarter Horse breed indicates otherwise. Production records have documented the existence of Roan Quarter Horses that produce 100% Roan foals. DNA tests have confirmed homozygosity in the genomic region that contains the Roan gene.
Thus, there is both observational and genetic evidence that is contrary to her statement...
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post #20 of 45 Old 08-21-2012, 09:53 AM
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Quote:
Originally Posted by Celeste View Post
If you can find documentation that the teacher is in error, you should bring it forward. But do it in a nice way. This person is highly educated, and if you come across as arrogant, she will no doubt embarrass you severely. Nobody knows everything. The entire genetic plan of all horses has not been firmly established or proven. She will welcome intelligent discussion. She will hate arrogant crap.
So is that how you treat your students? Make their likes a living heck because they present information to you in a way that makes you feel like an idiot? That's a real mature response and anyone who treats there students that way really, really needs to reevaluate why they are teaching to begin with as that is wrong and totally unacceptable behavior from ANYONE that is teaching regardless of the ages of the students.
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