The story about Angel and her unusual coloring brought together a couple of thoughts that have been on my mind lately. I thought I might explain them briefly here, and then expand on each in a separate post.
The shift from Mendelian Genetics to Molecular Genetics
When Pearson and Usher studied albinos, Mendel’s work had been only recently rediscovered. The results from their experiments with the Pekingese left them convinced that the problem was too complex for Mendel’s theories to accurately predict the outcome of their crosses. There were too many variables. In the hundred years since, science has not only identified many of the variables that eluded the two men, but it has begun to unlock the underlying mechanisms that produce the colors. Beyond just making modern genetic tests possible, this focus on the molecular level means that it is possible to understand the nature of color mutations in ways not possible before. This has implications for anyone interested in sound and ethical breeding decisions.
Just how many colors are there?
It is clear when reading A Monograph on Albinism in Man and Albinism in Dogs that the authors were not only grouping together different dilutions in dogs, but also blue-eyed white dogs that were in all likelihood spotted or merled. Because it is possible to test for specific colors, we now know that some colors that look alike are different things, at least on a genetic level. In some cases colors have proven to be unrelated even though the end result can be difficult to distinguish. Still other things are genetically related, in the sense that they are mutations to the same gene, but they differ visually – sometimes dramatically so. In other cases, they may be visually similar, but their pattern of inheritance is quite different. As a result, the list of known (and suspected) colors and patterns has been growing rapidly, while grouping and categorizing them has become more challenging.
What do we call all these new colors?
With each new discovery, the old naming system has been strained. Just as Dilution is a color in dogs, but a category of (visually) related colors in horses, many of the colors – particularly the pinto patterns – could more accurately be termed categories now. Yet many still speak of patterns as singular things. The most obvious problem has been with the what was once called sabino, and now sometimes jokingly referred to as KMOSS (“KIT Mutation of Some Sort”). What do we call these new categories, and the colors within them? This last topic should make an appropriate segue into the new paper on white markings, since that, too, is part of the same problem.
So bear with me for a few days while I pull these related thoughts together in a (hopefully) coherent way, and in no time we will be back to talking about horses again!