[accphotography]

Ok... where to begin? I guess I'll take it from the top.

I don't think reading the DW paper would have helped you. Most people (including myself) would need a translator to read that. I DID read it, but the majority of it went over my head. I got some out of it, but not much. The resulting conversation was a bit difficult to follow, however I got one very important thing out of it; the difference between sabino and DW. DW is a simple dominant, sabino is an incomplete dominant (think cream). In order for sabino to create a max white it must be homozygous whereas DW can do it with only one copy. Also DW in homozygous form is believed to be an ebryonic lethal whereas sabino obviously is not. DW in heterozygous form can be anything from simple roaning to a full blown max white. The key thing to remember here is that they KNOW where and what SB1 (and possibly others) are and thus they KNOW DW and SB are different. They may look the same, but genetically they are quite different. I think as they continue to find the other sabinos this will become much clearer.
I have seen enough to firmly believe there is a suppressor in TBs. There are certain lines where it is more apparent. Breed that line to a loud line and the results can be VERY interesting. A phenotypical fight between light and dark. LOL!

I do not see an obvious reason that splash could not be a combination of genes that are linked. That could, in part, explain why it has been so difficult to pin down. The only thing that throws me off on this idea is that they have narrowed it's location down pretty close and I think they might have discovered that it was multiple genes by now if it were. But... maybe not. Let's just say for a moment you are right so I can address your other questions:

KIT is linked to extension. According to the distance between them on the chromosome and my source (whom you know) their crossover rate is approximately 7%. You seem to have a good grasp of this linkage concept but I am unclear of your thoughts in one area. You say that KIT is linked to extension but then you mention it being connected to 'E' and the crossover to 'e'. You may know, but I just wanted to point out that it could easily be the other way around where the given gene is connected to 'e' instead of 'E'. The only reason I mention this is that I recently had someone comment that they thought KIT was connected to 'E' specifically in every case when in actuality it is connected to extension as a whole and whether it attaches to 'E' or 'e' depends on the individual animal's inheritance. I apologize if you knew that, i just wanted to clarify just in case.

Back to splash being a combination of genes. I could see that being a possibility, however I can't see the blue eyes being seperate from it. I can't really explain why I feel that way though. Call it a hunch. One of the reasons is that would mean there is a seperate blue eyed gene (which I know at least one person that thinks that is true, but I personally do not subscribe to that theory). A seperate blue eyed gene by itself does not really bother me, it's that frame also causes blue eyes that bothers me. Frame is nowhere near splash and thus would mean there are TWO seperate blue eyed genes... or that frame creates blue eyes within it's own gene (which it does) and there is still a seperate gene. This is possible of course, but I just don't buy it personally. I think the splash gene itself, like frame, creates the blue eyes. Think about this... you know that the reason splash horses are deaf is due to a lack of pigment in the inner ear. I firmly believe (and think it is a highly regarded theory) that the reason for blue eyes is white markings in a particular place triggering them. We can't always even see the white causing it, just like we can't always see the white causing the deafness. Ever seen bald faced horses whose white markings stops halfway across the eye and the eye is half blue and half brown right on that line? I see that ALOT. Other times when it is all blue, etc. but without the white going all the way, I think that goes back to the "seepage" theory MissRascal posted on EC. I think she compared it to a droplet on a paper towel? We see the actual droplet, but not necessarily how far the liquid spreads on the towel. Rambling again... So anyway, it is possible and I am not throwing it out in my own mind, but I don't think that's it. Might be though... lol.

I do absolutely agree that some breeds intentionally bred out blue eyes and white feet nearly completely eliminating genes like splash. Arabians were one breed that seemed to do that. Now look at the white craze in Arabians. If only they would wake up and quit calling splash "sabino". I honeslty believe they so pride themselves on their horses not carrying LWO that they love to insist they have "only sabino" and especially do not want to say they have "splashed white overo" because of the negative connotations that come with the word "overo". Now if APHA and PtHA would get on the ball and make some effort to split the genes and do away with the horrid "O" word.

Good theories and I LOVE doing this with you. One of these days one of us is going to hit a theory that we both like and we'll stick to it... and hopefully eventually be proven right. LOL!

ACC

[ryu2832]

Originally Posted by accphotography

Back to splash being a combination of genes. I could see that being a possibility, however I can't see the blue eyes being seperate from it. I can't really explain why I feel that way though. Call it a hunch. One of the reasons is that would mean there is a seperate blue eyed gene (which I know at least one person that thinks that is true, but I personally do not subscribe to that theory). A seperate blue eyed gene by itself does not really bother me, it's that frame also causes blue eyes that bothers me. Frame is nowhere near splash and thus would mean there are TWO seperate blue eyed genes... or that frame creates blue eyes within it's own gene (which it does) and there is still a seperate gene. This is possible of course, but I just don't buy it personally. I think the splash gene itself, like frame, creates the blue eyes. Think about this... you know that the reason splash horses are deaf is due to a lack of pigment in the inner ear. I firmly believe (and think it is a highly regarded theory) that the reason for blue eyes is white markings in a particular place triggering them. We can't always even see the white causing it, just like we can't always see the white causing the deafness. Ever seen bald faced horses whose white markings stops halfway across the eye and the eye is half blue and half brown right on that line? I see that ALOT. Other times when it is all blue, etc. but without the white going all the way, I think that goes back to the "seepage" theory MissRascal posted on EC. I think she compared it to a droplet on a paper towel? We see the actual droplet, but not necessarily how far the liquid spreads on the towel. Rambling again... So anyway, it is possible and I am not throwing it out in my own mind, but I don't think that's it. Might be though... lol.
ACC

Your 'friend' should be able to describe how the family of genes suspected for splash and frame cause the lack of pigment in skin and eyes. This mechanism is already well understood.

[RiddleMeThis]

Originally Posted by ryu2832

Your 'friend' should be able to describe how the family of genes suspected for splash and frame cause the lack of pigment in skin and eyes. This mechanism is already well understood.

She has. Acc knows that I have most likely read it already and chose not to put it in. Was there a reason for your post other than to attempt to bash Acc?

[ryu2832]

There was a long post hypothesizing about the mechanism of how blue eyes/white patches are formed in the overo family of genes why they are there then sometimes not, just pointing out that the genetic mechanism for lack of pigmentation is already known.

Just trying to put some straightforward information out there. No reason to hypothesize if the answer is already known.

She doesn't believe a word I say, so directing her to her friend seems to be the best way for her to answer the question.

[accphotography]

My friend's credentials are unrivaled. However I don't bug her without good reason.

If the mechanism is so widely known and acknowledged, why don't you post the information and your source so that those who don't know can learn as opposed to just saying it's out there somewhere. I have no desire to go digging for it as it was not really a question in my mind and not really pertinent to the purpose of this thread. The mechanism really has nothing to do with whether or not TBs carry splash and THAT was what this thread was supposed to be about.

ACC

[ryu2832]

Here is an excellent web page that explains how Neural crest cells migrate from the neural tube plate to eventually become melanocytes.

http://www.brown.edu/Courses/BI0032/...st/migrate.htm

Basically overo family white patterning genes disrupt the 'cell destiny' for the migrating melanocytes by prematurely triggering apoptosis.

The melanocytes are directed by different tissues as they develop, I didn't put the relevance of this together till just now. This developmental blocking of melanocyte migration is probably the difference in the final patterning phenotypes that you see, interesting. It also gives a strong indication of when during development these genes are active.

If you read all 4 pages then go to the Warrdenburg Syndrome page, it does a good job of explaining what defects are caused by mutations in the Overo family genes.

[ryu2832]

Originally Posted by accphotography

My friend's credentials are unrivaled. However I don't bug her without good reason.

If the mechanism is so widely known and acknowledged, why don't you post the information and your source so that those who don't know can learn as opposed to just saying it's out there somewhere. I have no desire to go digging for it as it was not really a question in my mind and not really pertinent to the purpose of this thread. The mechanism really has nothing to do with whether or not TBs carry splash and THAT was what this thread was supposed to be about.

ACC

I could care less about discussion about what hose is what color. What pattern is which. Ect....

But any discussion on developmental genetics, gene expression, or molecular genetics is going to catch my interest because it's what I do for a living.

Just as my first post here on the forum 'Black or Black Bay' got the color people all fired up, any post with real genetics in it is going to get me fired up because it is what I love.

[accphotography]

But my point is this thread WAS about which horse is which color, etc.......... it was not intended to be a thread about genetics.

developmental genetics, gene expression, or molecular genetics

I have virtually no interest in these things ^ and don't see how they apply to the thread.

ACC

[ryu2832]

Originally Posted by accphotography

Ok... where to begin? I guess I'll take it from the top.

I don't think reading the DW paper would have helped you. Most people (including myself) would need a translator to read that. I DID read it, but the majority of it went over my head. I got some out of it, but not much. The resulting conversation was a bit difficult to follow, however I got one very important thing out of it; the difference between sabino and DW. DW is a simple dominant, sabino is an incomplete dominant (think cream). In order for sabino to create a max white it must be homozygous whereas DW can do it with only one copy. Also DW in homozygous form is believed to be an ebryonic lethal whereas sabino obviously is not. DW in heterozygous form can be anything from simple roaning to a full blown max white. The key thing to remember here is that they KNOW where and what SB1 (and possibly others) are and thus they KNOW DW and SB are different. They may look the same, but genetically they are quite different. I think as they continue to find the other sabinos this will become much clearer.
I have seen enough to firmly believe there is a suppressor in TBs. There are certain lines where it is more apparent. Breed that line to a loud line and the results can be VERY interesting. A phenotypical fight between light and dark. LOL!

I do not see an obvious reason that splash could not be a combination of genes that are linked. That could, in part, explain why it has been so difficult to pin down. The only thing that throws me off on this idea is that they have narrowed it's location down pretty close and I think they might have discovered that it was multiple genes by now if it were. But... maybe not. Let's just say for a moment you are right so I can address your other questions:

KIT is linked to extension. According to the distance between them on the chromosome and my source (whom you know) their crossover rate is approximately 7%. You seem to have a good grasp of this linkage concept but I am unclear of your thoughts in one area. You say that KIT is linked to extension but then you mention it being connected to 'E' and the crossover to 'e'. You may know, but I just wanted to point out that it could easily be the other way around where the given gene is connected to 'e' instead of 'E'. The only reason I mention this is that I recently had someone comment that they thought KIT was connected to 'E' specifically in every case when in actuality it is connected to extension as a whole and whether it attaches to 'E' or 'e' depends on the individual animal's inheritance. I apologize if you knew that, i just wanted to clarify just in case.

Back to splash being a combination of genes. I could see that being a possibility, however I can't see the blue eyes being seperate from it. I can't really explain why I feel that way though. Call it a hunch. One of the reasons is that would mean there is a seperate blue eyed gene (which I know at least one person that thinks that is true, but I personally do not subscribe to that theory). A seperate blue eyed gene by itself does not really bother me, it's that frame also causes blue eyes that bothers me. Frame is nowhere near splash and thus would mean there are TWO seperate blue eyed genes... or that frame creates blue eyes within it's own gene (which it does) and there is still a seperate gene. This is possible of course, but I just don't buy it personally. I think the splash gene itself, like frame, creates the blue eyes. Think about this... you know that the reason splash horses are deaf is due to a lack of pigment in the inner ear. I firmly believe (and think it is a highly regarded theory) that the reason for blue eyes is white markings in a particular place triggering them. We can't always even see the white causing it, just like we can't always see the white causing the deafness. Ever seen bald faced horses whose white markings stops halfway across the eye and the eye is half blue and half brown right on that line? I see that ALOT. Other times when it is all blue, etc. but without the white going all the way, I think that goes back to the "seepage" theory MissRascal posted on EC. I think she compared it to a droplet on a paper towel? We see the actual droplet, but not necessarily how far the liquid spreads on the towel. Rambling again... So anyway, it is possible and I am not throwing it out in my own mind, but I don't think that's it. Might be though... lol.

I do absolutely agree that some breeds intentionally bred out blue eyes and white feet nearly completely eliminating genes like splash. Arabians were one breed that seemed to do that. Now look at the white craze in Arabians. If only they would wake up and quit calling splash "sabino". I honeslty believe they so pride themselves on their horses not carrying LWO that they love to insist they have "only sabino" and especially do not want to say they have "splashed white overo" because of the negative connotations that come with the word "overo". Now if APHA and PtHA would get on the ball and make some effort to split the genes and do away with the horrid "O" word.

Good theories and I LOVE doing this with you. One of these days one of us is going to hit a theory that we both like and we'll stick to it... and hopefully eventually be proven right. LOL!

ACC

This 4 out of 6 paragraphs in this post are about gene expression, regulation, and developmental genetics.

[ryu2832]

Did you take a look at the webpage, is it any clearer now?