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Test for roan RELEASED!!!!!!!

Ok, well it's a haplotype test, and it apparently only works on Quarter Horses and Paints (implying to me that there may be multiple roan mutations): http://www.vgl.ucdavis.edu/services/Roan.php" onclick="window.open(this.href);return false; I'm sure Horsegen will be here to enlighten us at some point. :bounce :bounce :bounce

Daylene Alford Sun, 05/03/2009 - 19:02

The problem with the Hancock lines is they are often bred roan to roan and that can skew the stallion numbers plus they often carry rabicano as well as classic roan. Not saying that they def are not homozygous just that I'm suspicious.

horsegen Sun, 05/03/2009 - 19:46

The test is only being offered to QH's and Paints because those are the breeds where the haplotype has been identified. I know it's hard to understand a haplotype test sometimes, but basically, horses are tested for a series of markers around the mutation. What we have found is that it looks like QH's and Paints all got their roan from the same place, so the same genetic markers have been passed with roan through those breeds from a common ancestor. It does NOT mean that QH's and Paints have a different roan mutation than other breeds! It just means we've found a way to track it in those breeds, so we can only offer the test for them.

Think of it this way...say that dun has been passed down from ancestral horses. Let's say all (or a lot) of ancestral horses were dun. They all had a variety of alleles at the markers around dun. Now...ONE of those horses goes on to be used to found the QH breed. He's the source of dun for the breed, so HIS markers are passed with dun to all his descendants. That's how we test to see if QH's are dun. Now, in theory, another ancestral horse could be used to found the Morgan breed, and HE'S the source of dun in that breed, so HIS markers travel with dun, which would mean the QH dun test wouldn't work for Morgans.

Now of course, this is not the case with dun, as the haplotype test works in almost all breeds of horses (some Spanish breeds appear to have something else), but this is how haplotype tests work. Just because a test is only available in QH's and Paints doesn't mean other breeds have a different mutation. However, since we've seen multiple mutations in KIT be responsible for dominant white in different breeds, it's certainly a possibility that these differences could exist in roan. And one or more of these differences COULD be lethal. But roan in QH's and Paints certainly is not. Yes, the Hancock horses could have other things like rabicano and sabino, but the TEST is for roan, and believe me, if other mutations were present that were making horses look homozygous when they weren't, the test WOULDN'T WORK. Some of these stallions have tested homozygous for roan, so obviously roan is not lethal in these breeds. We'll just have to see if different mutations are found in other breeds.

NZ Appaloosas Sun, 05/03/2009 - 21:05

[quote="rabbitsfizz"]Diane, I will try to get back to the Fewspot thing when that part of my brain comes back on line....do NOT hold your breathe it may be a while :sign[/quote]

Don't fret...I gave up holding my breath when my first kid hit the teen years! LOL

Diane

NZ Appaloosas Sun, 05/03/2009 - 21:07

[quote="rabbitsfizz"]Yes, I know about the Hancocks, which is what got me wondering about it being something else, maybe not Roan...and now we see that it only tests in QH's and derivatives thereof...see what I mean??[/quote]

So like the "dun" that Iberians exhibit not testing positive to the current dun test?? Something that leaves a roan phenotype but is a different gene mutation than roan found in other breeds?

Diane

PamelaTX Sun, 05/03/2009 - 23:10

[color=#8000BF][b]But horsegen how can we test if we don't have access to the sire or dam's hair??
The test can't be done??[/b][/color]

horsegen Mon, 05/04/2009 - 10:09

[quote]But horsegen how can we test if we don't have access to the sire or dam's hair??
The test can't be done??[/quote]

This is more an accuracy thing. Because this is a haplotype test, it's not 100%. Sometimes, in rare cases, a horse has a recombination event within the haplotype, so we see part of the roan haplotype, and part something else. If we have the parents, and we know that they're roan, that greatly increases the chances that we will be able to tell what's going on with the foal. We can see what the parents have and what each of them must have passed on--and whether those markers were traveling with roan or not.

This obviously doesn't stop people from sending in horses without the parents. Many people don't have access to them. (For example, when ACC sent in Lacy for dun, she didn't have the parents.) In these cases, we look at the genetic markers and many times can see if the horse is roan or not, simply because they have the markers or they don't. But if that horse turns out to be one of those wonky cases, it's more likely that we are going to send you a report that says the results are inconclusive. It's just the chance you take if you don't have the parents.

rabbitsfizz Mon, 05/04/2009 - 10:23

Horsegen that does not address the possibility that what may have been isolated is not in fact Roan as we know it in our horses, but Roan as it is known in the Hancock lines......

horsegen Mon, 05/04/2009 - 15:55

Well, what do you define as "our horses"? If you mean minis, then as I said, there could be a different mutation in minis. The roan haplotype works in QH's and Paints, which includes lines other than the Hancock lines. So all roan QH's carry the same haplotype, and that was passed through the Hancock lines as well. Other horses (besides the Hancocks) have tested homozygous for roan as well. So what this haplotype tests for is roan in QH's and Paints...any other breed may or may not have a different mutation. As with dominant white, there could be multiple mutations--we still call it all roan because the phenotype is the same, but the mutation may not be.

Sara Mon, 05/04/2009 - 16:31

I have to laugh at Rabbit's wording because I find myself thinking the same way. Some of us have little to no contact with American stock breeds.

You know what I just realized in the last few days? I have only ever seen one dun horse up close in person and she was a mustang cross. Her dam was part Kiger so she had craaaaazy dun factor. And the only roans I have ever seen are [b]one[/b] Quarter Horse (gorgeous gorgeous jet black roan barrel horse) and Welsh Ponies. I guess maybe I should stay out of the dun and roan discussions since I don't have the same frame of reference as most people! :lol:

accphotography Mon, 05/04/2009 - 16:43

I know several people in the same boat as you too Sara. I grew up in Texas surrounded by tons of stock horses so roan and dun seem so very common to me. :laugh1

JNFerrigno Fri, 08/05/2011 - 22:27

*reviving this from the grave*

Does the Roan Zygosity still only work on markers from QH and Paint Lines?

What is with the Hancock roans because I hear different things.

Have there been homozygous roans? Or is it still thought to be lethal?

RiddleMeThis Fri, 08/05/2011 - 22:40

In reply to by Daylene Alford

[quote=JNFerrigno]*reviving this from the grave*

Does the Roan Zygosity still only work on markers from QH and Paint Lines?[/quote] I believe UC Davis is testing all breeds with the marker test, but you can always email and ask.

[quote]What is with the Hancock roans because I hear different things.[/quote] No idea.

[quote]Have there been homozygous roans? Or is it still thought to be lethal?[/quote]There have been homozygous roans, and is no longer thought to be completely homozygous lethal.

Daylene Alford Fri, 08/05/2011 - 22:48

In reply to by Daylene Alford

The last I had heard was the roan in Brabants might look the same but was actually a separate mutation that could still be homozygous lethal. I have no idea if this has changed.

The roan that is found in QH's is not homozygous lethal and there have Hancock stallions that have been tested and proven by breeding to be homozygous for roan.

colorfan Mon, 08/15/2011 - 14:48

Let's see if I have this right. Please correct me if I am wrong.

I think of the the genes like a double set of chains, one set from each parent.
If one of the links is 'checked' the horse is hetero for that (what ever it is) if both links are checked, then homozygous.

So with roan it is like one link is divided into pieces and one in particular is checked with Quarter Horse roans.

Is this also how it works with the DW syndrome?

thanks,