General genetics question
Something that has come up many times on my facebook forums are ads for 100% Hets.
I'm a gecko person, so BP folks cut me some slack here. I own one single pet BP; it is black, brown, and yellow. I digress. For a trait that is recessive (and not visible in a het), say albinism in green iguanas, to get a 100% het, one would have to breed a normal to an albino. Of course, if you went out and grabbed a wild green iguana, you could be pretty certain it's normal, but let's say we're working with a captive bred population. My question is, how could you be 100% certain that one of the parents was a normal and not a het? How many generations of testing do most people use to give them that certainty? Or do you just maintain a lineage back to the WC animal? Thanks in advance for anyone who can clear this up for me!!! Noelle |
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I've wholesaled het albino boas as normals before and I know other people have done the same. Most people would be extremely happy if their normal ended up proving out to be het for something unexpected. Not sure if my answer helps or just raises more questions. :) |
Thanks April! That's pretty much what I thought, and I appreciate your taking the time to answer. I get nerdy about numbers, so when I see that someone is 100% sure of something, I tend to question how that's possible.
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Hets can be achieved in many ways. A visual to a non het for example. Another being a visual to a het both of these examples would be 100% hets, a third being a het to het, these being 66% hets until proven het, and finally a het to a non het, these being 50% hets until proven otherwise. Again sorry if I misunderstood. |
Statistically speaking, you cannot fully disprove a het. Even homozygote to heterozygote. There is always the possibility that one is experiencing some sort of extreme string of luck (good or bad being whether you want it to prove or not) no matter how insanely long the string might be. This is species-agnostic and purely an embrace of the theory of the math involved.
Practically speaking, beating a "bad luck" het horse is something almost any keeper would want to make a call on so as to stop spending resources on an inefficient/ineffective animal for a particular project's design/needs. This basically means drawing a line to declare whether one considers it functionally or effectively disproven even though it cannot be mathematically disproven (we can infinitely approach a chance of zero without reaching zero). For me, that make-a-call/draw-a-line point might be twenty offspring. There have been genuinely poor luck cases where twenty offspring were not enough to get the job done, though, and waiting for thirty settled it with production of a recessive homozygote near the end of that string. Kind of rare to take that long of a string, though, in my experience. If I have an animal with bigger clutches (like a sulcata tortoise), I would give it the whole season with several clutches only because I could. If I were dealing with a leopard gecko, I would want to give the benefit of the doubt and at least go for twenty hatchlings before calling it one way or the other. Pursuant to the words above, it is kind of upsetting to me when people make their calls at strings of ten or even less. They sometimes then make efforts to raze reputations on results that I have achieved somewhat often with proven/known hets (in both 10-deep good strings and 10-deep bad strings). Breeders and sellers do not deserve that kind of treatment in my opinion. When I see people act this way and go on the warpath based on such limited rolls of the dice, my impression is that they really have no business dealing with hets if they cannot keep the math in perspective and give people a somewhat fairer shake. These types are super happy when independent acts go their way and super infuriated when independent acts do not go their way. Hets are crucial to almost all of our morph projects as a community of reptile keepers and breeders. I have projects consisting 90%+ of hets paired to key homozygotes to ensure what the offspring will genetically be based on immediately apparent appearance once hatched. For one of those projects, I am one of only around a dozen breeders in the US. If we all abandoned hets and worked only with homozygotes, there would be a whopping two to three of us at present. Far less fertile a landscape for customer supply and breeding project opportunity. |
Bran, I admittedly don't know anything about BP morphs, so possibly there is a way to know that a trait is heterozygous. But with a trait such as albinism in lizards, to be 100% certain a baby is het, one parent must be homozygous normal and the other must be homozygous albino. My question is, how do you know the normal parent is homozygous and not heterozygous?
Nick, I think you understand my question. I'm a mathematician, so I tend to be fixated on sample size. I do understand the need for playing the odds, as far as continuing the hobby. Here's the reason for my question. On the facebook forums, there is quite a bit of behind the scenes arguing over what can or cannot be claimed in an ad. Again, let's just say we're discussing iguanas, and many of you will know where I'm going with that. I don't believe there's any way to claim a normal looking offspring is 100% heterozygous for a non-visual trait. |
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If you are saying the deviating-from-wild-type trait is visible in homozygous form (like, say, amelanism), then there would be no visual difference between a homozygous wild type animal and a heterozygous animal, but a homozygous amel animal would be determinable by appearance. Going back to the first block quote section, though, if one parent is a visual morph, then all normal-looking offspring would be known hets. If an ivory sulcata, a Tremper albino leopard gecko, or a pied ball python drops a fertile egg (ever), then that fertile egg is at least a het (with 100% statistical certainty). |
Ahh, the little lightbulb just went on. I see where part of my thinking is off. Sorry for the confusion; it was entirely on my part.
I appreciate the explanations! Thanks everyone! |
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