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Some genes I am confused about - homozygousity & OLWS

Ok a quickie about me - I am absolutely GAGA about black and white Overos!!! They are my absolute favorite. A problem I have run into lately is finding the right conformation within the potential stallions I find - which is really a whole other story(they are nearly non-existant and I am rather picky). Recently I bought Chance(grulla) and Cody(dun) who are full sister and mother to one of the mares(red dun) I had already bought. I have a serious grulla fetish growing now! So I'm sitting here doing my wonderful color research about my mares, and it dawns on me, a big freaking DUUUUUUUH! I have a grulla now - when bred to homozygous black I will get either black or grulla, no ifs, ands, or buts. So I'm all juiced even if I have to wait a few years because she's only 3 and I want to get her fully trained with miles on her before I breed her. My question I guess, while thinking about all this... She is not homozygous obviously because she has a red dun full sister. So at what point can a horse become homozygous? There is tons of color research, but I haven't seen a whole lot on when and how homozygousity occurs. A potential stallion I have found for whichever mare I choose to breed is homozygous, but his grandsire on his dams side is the sire of my gelding(the alien bay with silver points) and he was NOT homozygous. Another questions is about OLWS. My mom has a dun Paint mare whose grandsire 3 gens back on her sire's side was Gambling Man. He was OLWS+. He is also this stallions sire, and he is also OLWS+. Of course if my mom agreed to let me breed this mare I would get her tested first, I have already tested my black and white mare and she is OLWS+ so that's a no go. Correct me if I am wrong please. All frame overos are not OLWS+. I am wondering how exactly it is passed on. I can't find this information. I have read a lot about it but have never come across whether it is ALWAYS passed on if there is a + parent. I hope you understand what I am asking LOL I would in no way, shape or form breed two OLWS+ horses to each other. I am just trying to get a better understanding on the genetics of it. Thanks and sorry for the long post :)

horsegen Fri, 06/05/2009 - 19:19

[quote]I don't mean to hijack this thread, but Horsegen, regarding the O/n vs Oo being due to it being a test for a disease... I've seen het silver listed as Zn. Is that "wrong" then, and proper "terminology" should be Zz? Just curious :) Should the n be capitlized, lower case, or does it matter? Just want to write/type it properly :)[/quote]

Well, recently, when we started getting all these tests for patterns and dilutions that breeders were interested in, I think it was decided that it was simpler (and easier for owners to understand) if we started using the N/"other color" system, because then it becomes very obvious whether the animal has that dilution/modifier or not. It gets confusing for non-color enthusiasts to keep track of what's dominant, what's recessive, what the various genotypes mean--so by using this system for these new genes, someone can simply look at their results and say, "Okay, my horse has champagne." Or, "No, my horse does not have silver." If you see the Z, that's silver, if you see N/N and no Z, that's more clearly a "No." We've recently started using this system for almost everything!

horsegen Sat, 06/06/2009 - 12:23

I work for UC Davis. I'm in the research division, so I'm one of the people who tries to find the mutations for these genes so that we can offer the tests to you, the interested horse owner! I'm working towards my Ph.D. in genetics...the research on Cerebellar Abiotrophy is mine. (You can read about that disease on our web page.) I'll be done in 15 months...woo hoo! :toast