General genetics question

[rcarichter]

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

 

[AbsoluteApril]

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?

No way to be certain really unless you bred it to all known recessives and didn't get any visuals. I don't know anyone that would purposely breed to prove an animal is not carrying morph genetics. Most people will assume a normal is a normal unless they know the breeding that produced it. Even if it's WC, that could still end up being het for something.

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.

 

[rcarichter]

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.

 

[bcr229]

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.

I only put 100% het on animals I either produced or proved out.

 

[rcarichter]

I only put 100% het on animals I either produced or proved out.

But, again, how can you be sure one of the parents is normal, and not het, if you're dealing with a trait that is non-visible as a het? Even if you bred it, you still can't be sure.

 

[blbballs]

But, again, how can you be sure one of the parents is normal, and not het, if you're dealing with a trait that is non-visible as a het? Even if you bred it, you still can't be sure.

I may not be understanding this, and forgive me if I am not getting your question, but if we breed a homozygous clown gene ball Python to anything we will get all 100% het clowns, so what does it matter if one of the parents in your example are 100% not het for anything or not?
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.

 

[nickolasanastasiou]

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.

 

[rcarichter]

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.

 

[nickolasanastasiou]

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.

Let me break that up a bit.

to be 100% certain a baby is het, one parent must be homozygous normal and the other must be homozygous albino

Half of that is so. One parent must be a homozygous albino. The other could be a heterozygote or a homozygote. For either secondary-to-the-albino parent, normal-looking offspring would certainly be hets if parent/breeding exclusivity is assured. Only the homozygous albino parent is needed to be 100% certain a baby is a het for albinism.

how do you know the normal parent is homozygous and not heterozygous?

As alluded to in the earlier post, you never know. You just believe or have confidence since the possibility of the alternative always exists on some statistical level regardless of the sample size. It just becomes less probable of being a het with more data. Still possible, but less probable.

I don't believe there's any way to claim a normal looking offspring is 100% heterozygous for a non-visual trait

If you are saying the deviating-from-wild-type trait is not visible in homozygous form (like, say, a digestive enzyme change instead of a color change), then there would be no visual difference between a homozygous wild type animal, a heterozygous animal, or a homozygous recessive animal (I am just using recessive as an example mode of inheritance here) and so appearance would be a useless criterion for determining difference.

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).

 

[rcarichter]

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!

 

[nickolasanastasiou]

I consider the conversation an investment. Others will read this and surely find benefit, so thank you for asking.

 

[AbsoluteApril]

Glad it all helped in the end. I was totally confused on your original question, was trying to figure out why someone would want to prove out a normal as being only a normal

 

[nickolasanastasiou]

Glad it all helped in the end. I was totally confused on your original question, was trying to figure out why someone would want to prove out a normal as being only a normal

There is one example species I can think of and that is in the leopard gecko keeping community. Leopard geckos have three known locus-incompatible amelanism/albinism types/"strains". It is widely frowned upon to mix any single type with a type other than itself. If one wants to make a multi-gene combination morph, sometimes a breeder tries to establish reasonable confidence in the animals being worked with and that can mean test breeding to "disprove" for an undesired albino type that may or may not be known to exist in the base animal's lineage. The aim here is to produce the resultant hets (incidentally) with the hope of not getting the test-bred albino type that season so that the following season can be focused on the target albino variant once some confidence has been established that the tested-for type is likely not present in het form in that breeding animal being tested. Another goal is to maintain outcross stock for other projects. Animals intended for blank slate outcross stock may be test bred similarly with the goal of making sure the adults intended to produce future outcross-useful offspring (and the adults themselves) are not likely to be in possession of any recessive genes that could impact any other morph project.

Since BPs still get imported, BP people (to my admittedly limited knowledge) have little to no need to do things like I have mentioned, but leopard geckos are a different kettle of fish in terms of injecting fresh lineage into projects. With leopard geckos, it is pretty much Zeus and Hera or Oedipus and Jocasta for the most part in captive populations in the US, so that is why such measures may be taken.

 

[AbsoluteApril]

Yes, I understand about leopard gecko albino strains and wondered if that's where she was coming from. Similar issue with boas, there are two incompatible but similar looking strains of albino which means it's important to know which strain you are buying/selling (when the original two strains were crossed to see if they were compatible, the resulting normal appearing double hets were wholesaled off as normals into pet stores, from what I've read).

In general, proving out a normal as only carrying wild type genes is not something one comes across. The statement about being able to trace back to WC origins had me wondering as all morphs came from WC origins, simply being able to trace it back doesn't ensure the animal isn't a het (which I know you understand).

Feel like I'm talking in circles and simply making it more confusing haha! *goes back to my hidebox*

 

[nickolasanastasiou]

Yeah, aside from an exception like the leopard gecko or boa situation, the concept would be seemingly rare in my opinion and I cannot recall an instance or example beyond those.