Announcement re Roan/Tobiano's!

[quote="accphotography"]Well I did find a tested SB1SB1 TOto.[/quote]

Is SB1 close enough to TO or Kit that it links as well? Does it link to extension?

Sabino 1 is in KIT and thus links to extension.

I'm with Rabbit sort of got it then got all tangled..Thank you Danni now I can go back and read it all again :pop

I would be intensely interested to see any cases of homozygous tobi horses with roan. I have seen homozygous tobi horses with lots of flecking, but not ROAN homozygous tobi horses. Roan and tobiano do work in the same manor. Both cause disruptions in the tyrosine kinace receptors, tyrosine being the amino acid necessity for oxidizing pigments to produce color. Without it pigment production halts. The difference between roan and tobi (and sabino and dominate white for that mater) is not what is going on but at what point the disruption occurs. The statistical likelihood of roan and tobiano occurring on the same strand of DNA is remarkably small.

Extension (MC1R) is right up next to the centromere on chromosome three. KIT is all the way down at the end. Ch. 3 is somewhere around 150 million base pairs long, with that half of Ch. 3 being approximately 100 million base pairs (wich is a rather average length). Even with these statistically good odds of crossing over Extension and Kit are only seldom inherited separately. Hence why the the mare Tamera Wess the red roan mare who founded a whole legacy of roan western pleasure horses is not known to have a single blue roan offspring with roan linked to a dominant black gene. If crossing over between extension and KIT is a once in a hundred years sort of deal as it seems to be then the idea of roan and tobiano crossing over so that they are inherited together would be a once in a million or even rarer chance. You are no longer talking 100 million base pairs between but a few hundred thousand if that. Even with those rough estimate that would be a .000,001% chance. And that is of course if it is even physically possible for a viable offspring to be produced with such a modified KIT gene.

So is it possible to have tobi and roan on the same strand maybe, but the statistical weight against such an occurrence is staggering and it would mean whole lines of horses that produce nothing but roan tobianos and to my knowledge no such line exists (you would think such a think would be pretty well talked about). Such a chance is so slight you are just as well to treat them as different alleles of the same gene, because they absolutely are different versions of the same loci.

Hello Ammit and welcome!

Thank you Jenks. I hope my post does not come off as argumentative. I would be insanely eager to see any evidence of crossing over between tobi and roan because it would give us a whole knew understanding of what is going on. Ahh science. :ymdaydream:

No of course not....Yes, horsegen said it was a less than 1% chance (was that this thread?) It's all starting to blend together....!!! LOL

Duh I think I missed the page where she had posted.

I should have joined this sooner when Monsterpony first pointed it out. I lived like 2 miles from Horsegen's lab! I could have gone over and seen it. :hammer I did get to hang out in Dvorak's wheat lab a few times which was cool but lets face it wheat is just not as cool as ponies.

[quote="Ammit"]The statistical likelihood of roan and tobiano occurring on the same strand of DNA is remarkably small. [/quote]

And what about tobiano and SB1? Would that not be approximately the same chance?

[quote="Ammit"]Hence why the the mare Tamera Wess the red roan mare who founded a whole legacy of roan western pleasure horses is not known to have a single blue roan offspring with roan linked to a dominant black gene. [/quote]

That wouldn't happen. She only has 'e' to pass so she would NEVER have had a foal with roan attached to 'E' unless the sire contributed it.

No there is no reason that SB1 and Tobi would have identical chances of crossing over as tobi and roan since in all likelihood sabino 1 and roan are not in identical locations, just in the same close neighborhood. I also have never seen any proof of a homozygous tobiano horse who has tested positive for sabino 1 (though I would be interested to see it). I have certainly seen lots of tobiano horses that are homozygous that have strong appears of the phenotype expression that we refer to as sabino, but since sabino 1 is the only form of sabino proven by actual mapping to exist at this point we can not prove that those horses have a distinct sabino gene. Or that indeed that sabino look in those horses is just an effect of tobiano itself. It certainly would be possible. It would be really cool to find out if tobiano genes have a sabino modification linked to them and if they do is there unique strains of sabino/tobi linkages that could be used to trace back the origins of different tobi families. It would be some really interesting research. You have spured me to do some more looking at homozygous tobianos.

I was not talking about foals of Tamera Wess. ;-) As I said she founded a legacy I believe her descendants number in the thousands now, and there are I believe 4 generations of horses decedent from her now though they may be nearing 5 now.

Ammit- very interesting .. our Stallion (Blue Roan Tobi) seems to have his red gene and roan linked and the black gene and tobi linked..from what you are saying that is very likely to be the case I gather?
He has sired a number of foals in the US (he is in Australia now) and there is one bay dun roan homozygous tobiano that we are going to have tested for the roan gene as she would be the only one that got both the tobi + roan from him... but I am thinking that the chances of this is very unlikely if not impossible, so will be interesting-- her roaning must be coming from some other gene I guess... also he has a blue roan daughter that we may get tested for the black gene to prove the link with his red gene and roan. We have 2 of his babies a red roan filly and a black tobiano, so that kinda seems a bit obvious re the linkage extension and KIT :smile:

Oh Sampson! We had a discussion about him on my forum when we were talking about kit mutations (nothing bad I promise where where just using him as an example of a roan tobi siring either roan or tobi but not both). I would say either the filly is not a classic roan or she is not a homozygous tobi. By the way your colt Flit has the coolest markings.

[quote="tbtash"]Ammit- very interesting .. our Stallion (Blue Roan Tobi) seems to have his red gene and roan linked and the black gene and tobi linked..from what you are saying that is very likely to be the case I gather?
He has sired a number of foals in the US (he is in Australia now) and there is one bay dun roan homozygous tobiano that we are going to have tested for the roan gene as she would be the only one that got both the tobi + roan from him... but I am thinking that the chances of this is very unlikely if not impossible, so will be interesting-- her roaning must be coming from some other gene I guess... also he has a blue roan daughter that we may get tested for the black gene to prove the link with his red gene and roan. We have 2 of his babies a red roan filly and a black tobiano, so that kinda seems a bit obvious re the linkage extension and KIT :smile:[/quote]

Nice chest! I'm obsessed with chests suddenly.....My arabs are much narrower.

Ok, maybe I'm missing something obvious. The actual location of roan has not been found yet, so how can you say it's far less likely for TOTORNrn to happen than it is for TOTOSB1sb1 to happen?

Tbtash: I'd love to see photos of the bay dun roan TOTO. If the roaning looks anything like the one you posted than I think you may have proven it's indeed possible. I would not be willing to say "it must be some other type of roaning" until I not only saw the horse for myself, but the roan test. Maybe I'm too open minded...

I never once said it was far less likely. Not sure where you read that.

The horse she posted is not homozygous tobi

[quote="Ammit"]No there is no reason that SB1 and Tobi would have identical chances of crossing over as tobi and roan since in all likelihood sabino 1 and roan are not in identical locations, just in the same close neighborhood.[/quote]

That's what I got out of this ^.

I know she's not, that's why I asked for photos of the one that is and said "if she looks like that one...".

This horse is homozygous tobiano and tested positive for SB1:
http://www.hamiltonstables.com/Traveler…" onclick="window.open(this.href);return false;

Aha Found it! I knew the reason we where talking about your stud was because of some impossible claim on a foal by his old owners. I found the link.

http://www.spottedfawnpaints.com/Dun.asp" onclick="window.open(this.href);return false;

The supposed Dun Roan Homozygous Tobi is Dun In Montana. She has zero evidence of any roan on her. These are also the people who say on the page "a stallion who is built and bred for the reining gene " :?

Umm... First no where does that stallion claim to be sabino-1 nor does it say anything about him having been tested for sabino at all. The only thing they said they tested was for tobiano. There is nothing here showing a link between a copy of tobi and a copy sabino. This stud is not even particularly heavily marked by sabino.

I also have zero idea how you could get "far less likely" for sabino 1 versus roan to cross over with tobi out of "in all likelihood not in identical locations." What you got out if is not even close to what I actually said, just as what you got from that page is not close to what is actually on it. I don't mean to be rude but both those statements are really quite far off from what was actually stated. :cry:

I agree, she doesn't look roan, but that's an old photo and I'd like to see an update.

Haha... I didn't say the website said he tested positive for sabino. I've been talking to his owner. She told me he tested homozygous tobiano and heterozygous SB1 and they have at least one other that did as well (one of his foals).

"Heavily marked by sabino" is most certainly not necessary to test positive for SB1, as I'm sure you know.

When I see actual data showing such a thing as tobiano linked to Sabino 1. I will be excited to see it. I do not consider he said/she said to qualify as worth while information.

Would a copy of the test results from UKY satisfy you?

FWIW, again, as I'm sure you know, SB1 can be this minimal and likely even less:
http://www.mikarmafarm.com/outlawrtlook…" onclick="window.open(this.href);return false;

[quote="Ammit"]When I see actual data showing such a thing as tobiano linked to Sabino 1. I will be excited to see it. I do not consider he said/she said to qualify as worth while information.[/quote]

So another person who likely doesn't consider breeding data valid. Interesting.

It says on the website they have never bred him "We are very proud of him and we look forward to breeding our Flash fillies to him in the future." The website that was updated last month at the latest, and has all their 2010 foals listed but none by this stallion. I honestly think there is another confusion going on here. They do own a stallion who has one tobiano gene and sabino gene and he does produce foals that are either tobiano or sabino, and his foals clearly show that. Not only is there no evidence of a sabino 1 and tobiano link on the stallion you posted, (who has never been bred despite you saying his foals have it) but there is no evidence that such is the case on the sabino tobi stud they do have. If you are going to be researching genetics and informing others about it you need to read what sites say carefully, you can't just go around mixing things up.

You are just making stuff up and calling it data! So yes I do want to see a copy of the test results. I plan to email the owners and ask.It is infuriating to try and have a conversation about genetics with a person who can't even keep two studs straight. :BH

Honestly I am done. I will ask them what his test status is, and continue believing there is no such thing as a tobi linked sabino-1 until I see other wise. Chow!

[quote="Ammit"]It says on the website they have never bred him "We are very proud of him and we look forward to breeding our Flash fillies to him in the future." The website that was updated last month at the latest, and has all their 2010 foals listed but none by this stallion. I honestly think there is another confusion going on here. They do own a stallion who has one tobiano gene and sabino gene and he does produce foals that are either tobiano or sabino, and his foals clearly show that. Not only is there no evidence of a sabino 1 and tobiano link on the stallion you posted, (who has never been bred despite you saying his foals have it) but there is no evidence that such is the case on the sabino tobi stud they do have. If you are going to be researching genetics and informing others about it you need to read what sites say carefully, you can't just go around mixing things up.

You are just making stuff up and calling it data! So yes I do want to see a copy of the test results. I plan to email the owners and ask.It is infuriating to try and have a conversation about genetics with a person who can't even keep two studs straight. :BH[/quote]

Go for it. I don't have time to deal with people who takes websites as gospel over owner's words. I [b][i]don't[/i][/b] "make stuff up" and I'd greatly appreciate if you'd refrain from accusing me of doing so with no evidence. :evil: You may not like me, but that does not give you the right to call me a liar.

I don't think I've ever met such a "confident" newbie. Temper, temper.

Come on ladies, please be nice, this is a discussion group so yes we are going to have disagreements but lets not fall out over it please. :-t

You both have valid points to make and it has been interesting having a new person's viewpoint.

Please don't make me lock this thread. I was really enjoying the discussion up to this point.

You have both gotten out of line on this one.

ACC is without a doubt one of the best researchers we have on the board. If she has made a mistake (and I'm not saying she has). Then it was an honest one and she should be allowed some slack.

Ammit is also no color newbie.

I look forward to more civilized discussion on this thread.

Admin

Hi again :smile: Will definitely post the tests results re Anna- Dun Roan Homozygous Tobi.
According to the breeder who although may not be a colour geneticist has had a lot of experience in seeing the colours in the foals..did tell me that when Anna was a foal she had the white hair through her enitre body coat and all signs that she was a roan-- so will be interesting--- I personally can't see the classic roan myself but I have read on this forum that there can also be a minimal expression of the gene.

Ammit-can I ask for your forum address, no worries with me that Sam came up for discussion ;-)

ACC-I will try and track down her latest pics as I am in touch with the owner re her tests.

Cheers

Here's an example of a very minimal roan:

http://www.crossspur.com/files/pcBronsi…" onclick="window.open(this.href);return false;

All right I wanted to go to the source and gets the facts straight before making a response. First I apologies for my temper. I found the lack of supporting details and ever changing story to be very frustrating. I believe there is a combination here of accphotography misunderstanding information from the stud owner (like if this stud had foals or not yet) and the stud owner misunderstanding sabino all together. I do however feel that accphotography did indeed jump to conclusions that there simply was no data to support. To accphotography herself it has nothing to do with not liking you on a personal level. I don't know you. I do however dislike it when people are trying to prove something by just tossing up links without supplying the corroborating data, particularly when it is something that really needs to be proved to be believed. Some of use do study genetics for a full time living, so to us making sure we have spot on correct data is really important, when someone insists the current paradigm is wrong, we are naturally going to want to see the data. Science by it's very nature is about saying "prove it." But I do realize that for most people this forum is about the joy of horses not about chemical pathways and molecular biology. So I do apologies.

Let me share what I have found out though. Of course the starting point was Fortunes Crimson Traveler's webpage. The website clearly states that he homozygous tobiano and carries a KIT gene and that he was tested University of KY. I sent an email to UKY but have not heard back from them yet (I will get to that in a second). I then emailed the owner and asked her if her horse had tested positive for the sabino-1 gene. She told me simply "Yes, he has one copy of the sabino1 gene." I was honestly very surprised by this and quite shocked. I sent her another email congratulating her on this rarity and asking if UKY planned to do any follow up research with him, and asked her about foals he might have also testing positive for this. I also asked her point blank "Is it sabino-1 that he has been gene tested for" since she never answered me the first time.

She was surprised by response for a number of reasons. She confirmed he has no foals and will not until next year. He also was never tested at UKY desipte the page saying so, but was instead tested at UC Davis for tobiano, but not for sabino-1 as far as I can tell. She then went on to inform me that they know he has sabino-1 [u]because he has a blaze[/u]. She told me how lots of homozygous tobiano horses have sabino-1 and he is not the first, you can tell because if they have a blaze is probably means they have sabino-1. ;-)

So clearly there was some confusion by the owner here, and she did not explicitly state that he was never directly tested for sabino-1 but I honestly have my doubts he ever was. (Not to mention the fact that he looks nothing like a sabino-1/tobi.) So since he was tested at UC Davis I sent them an email asking directly about this horse and about the possibility of a tobi sabino-1 linkage.

Davis had this to say "If both parents are tobiano they can each contribute a tobiano gene to the mating and the offspring would have two copies of tobiano. If one or both parents also had the sabino1 gene they could contribute the sabaino1 gene [i]independently of the tobiano gene.[/i]" So Davis has confirmed that horses do not give tobiano and sabino-1 at the same time (ie not on the same strand of DNA) and that they have never had such a case. The responder then went on to basically say "prove it" as well, and suggest I ask his owner to produce records of this test saying he is homozygous tobi and a carrier for sabino-1.

It is my personal belief that the owner of Fortunes Crimson Traveler has made the honest mistake of confusing sabino-1 the specific gene and sabino the generic phenotypic term. I do not say so to discredit the owners horsemanship in the least, they have some lovely animals but are a bit confused on the exact nature of what they have.

So let me make sure I have this correct. SB1, classic roan, DW, and tobiano will all exhibit linkages and by the nature of very close proximity to each other will only be found together if one is inherited from each parent (unless in very rare cases).

I'll need to make some changes to the color calculator....