I am still playing catch-up with the Splash Project page, with more homozygous horses (like this Paint mare owned by Julia Lord) to add, as well as links to some interesting negative tests. I did not realize that an unexpected week away would put me quite so far behind!
Until I am caught up, there are a few important bits of news. A few horses have surfaced that have tested positive for one of the other versions of splashed white, SW2. One can be seen here. Reports are that she is SW1/SW2. It has also been rumored that the Quarter Horse stallion Colonels Smoking Gun carries the SW2 version. Whether his is the only line, or if there are others, is not yet known. So far I have not heard of a horse that has tested positive for SW3. Hopefully some of those will turn up soon.
It is interesting to note that the linked SW2/SW1 mare has somewhat less white on her body than the horses that have been testing homozygous for SW1. That will be something interesting to watch for among the horses that have a combination of two different versions. Even though their basic look might be the same, as has been reported, there may yet be visual differences that people good at pattern identification may see.
And that brings me to my own limitations. I have said that I am a phenotype researcher; I look at and analyze the visual appearance of horses. I look at a lot of horses, and I study family groups and trends within them, but I am not a molecular researcher. I have had what amounts to a crash course in the molecular end of this subject in the last ten years or so, because it has become increasingly relevant if one wants to grasp the current research. But it goes without saying that at that level, there are gaps in my knowledge. And I will likely never be as comfortable with that part as I am with determining tonal and pattern differences. So be aware, when reading this blog, that I am first and foremost an artist by trade.
I try to keep that limitation in mind. It is very important to me that this blog not perpetuate bad or misleading information. I have tried to simplify concepts presented here, because most readers are either artists or breeders or owners, but simplification itself can be misleading. I’ve been told that this is the case with the “one slot” explanation for KIT mutations. I was fortunate that someone with far more background in the technical end of genetics was able to point me to some relevant research, and hope to post a clarification in the near future. For the moment, though, let me throw down a marker that the subject of KIT mutations is more complex than that.
I also have questions about the nature of alleles, which others have expressed in other venues. The question I have had is whether or not these different versions of mutations (like SW2 and SW3) occur independently of one another, or does the original mutation get altered as some point. That is, was there one splashed white (presumably SW1 since it is most common and occurs in very old breeds) that changed into SW2 and SW3? Or did completely new mutations occur in the same general area and affecting some of the same functions? Since each dominant white mutation was like that – separate instances of similar mutations – we know that the latter scenario can happen. Is that what usually happens? Knowing this might tell us something about where to expect – or perhaps where not to expect – the less common (and perhaps as-yet-unidentified) versions of splash. I hope to send out some queries along those lines, and report back what I find.