Sunday, July 22, 2007

And so it follows...

If Iset is a pattern like Ag grey... it would be found at the same genetic location as Ag grey.

Any one sheep could only carry two pattern genes. Therefore, an Ag Katmoget would not be able to also carry the Iset Pattern gene. Any heterozygous Katmoget, Gulmoget, or Grey sheep that didn't already have another pattern could theoretically carry the Iset pattern as well. But a homozygous Katmoget, Gulmoget, or Grey sheep would not be able to carry Iset. So it shouldn't show Iset either. Now, Solid, is also a pattern. But Solids sometimes go Iset, so maybe that sheep has one Solid gene and one Iset gene...

Since Grey and Katmoget patterns lighten the main fleece so much, it might be hard to tell if they are also Iset. I'm not sure I would recognize an Iset-Grey myself. Unless, maybe I had been watching it closely from birth for that very purpose.
Recognizing Iset in Solids and Gulmogets is easier? I don't have Gulmogets in my flock yet. (emphasis on the YET.) So I really can't comment on Gulmoget fleeces at all. I would love to hear imput from any breeders that have been working with Gulmogets about the occurance of Iset in those fleeces.
Saying that a homozygous Gulmoget could never go Iset, until perhaps old age, feels like I'm right out at the tip of that big limb I hopped up on in yesterday's post. I'm sure that is exactly where I am too. And what if the whole thing snaps and Theory 1 is blasted out of the water.....?
Well then, I would KNOW for sure Iset is not a pattern. The occurance of it would have to be hidden in some other place in the genetic code. After enough chipping away it will be found in a familiar genetic location or we'll discover a new location.
Who wouldn't like to know which pretty little lambs are going to be Iset by the time they are one or two years old? Maybe a lot of flock owners. Some people want mystery in their Shetlands and don't appreciate everything being pinned out like butterflies to a board. I can respect that.
I would be less reluctant, however, to have Iset in my flock if I understood how it was passed on to offspring. If I knew something concrete about it-like it will show if one gene is present-or it takes two genes to produce it-I could make more appropriate decisions about terrific Shetlands that just happen to be Iset too.

For now I'm going to scrutinize my flock for evidence that supports or defies the "Iset as Pattern" theory. Thinking out loud like this helps me clarify my ideas. I may be the first one to disprove my own theory. :)

1 comment:

Michelle at Boulderneigh said...

I love learning from other's postulations, so postulate away! For instance, Linda Wendelboe and others have reason to suspect an Extension gene in Shetlands, but it's not proven (I think) or well understood. Juliann Budde and others have been working on understanding all the possibilities of the polled and horned genes in Shetlands, which gets quite complicated when you consider that sheep can have "horned ram, hornless (not the same as polled) ewe" genes, "polled ram, horned ewe" genes, and many other combinations of the above, as well as the possibility of a separate scur locus. I hear the Brits think we North Americans obsess too much when it comes to the genetics of color, markings and patterns. They use the terms as descriptions of what they see, not to "nail down" genotype. I would love to have the resources and lifespan to explore Shetland genetics to my heart's content; it's all fascinating to me!