Homozygous doms

[OhhWatALoser]

http://www.owalreptiles.com/geneticinfo.php

.... So what does it take to prove a dominant morph is in fact a dominant morph? I only know of two ways, statistics and complexes.

We will start with breeding a Pinstripe to another Pinstripe. The offspring statistically will be 25% Homozygous Pinstripe, 50% Heterozygous Pinstripe, and 25% Normal. Now since Pinstripe is a dominant morph, the homozygous and heterozygous forms look exactly the same. We are unable to tell them apart, so what we have is all the Pinstripes being 33% possible homozygous. 25% homozygous to 50% heterozygous which is a 1:2 ratio or 33% homozygous:66% heterozygous.

Now unlike possible recessive hets which can be proven out through producing visuals, we need to use statistics to prove homozygous dominant morphs. When the homozygous Pinstripe is bred, it will always produce Pinstripes. Once there have been enough eggs of all Pinstripes to call it something other than luck, you have proven it homozygous. One normal offspring will quickly prove the animal to be heterozygous. How many eggs you need to see is completely up for debate, but to give you the odds of a heterozygous Pinstripe producing all Pinstripes, here is a little chart.

Chance of heterozygous producing all morphs
# of eggs Fraction Percent
5 eggs 1/32 3%
10 eggs 1/1,024 .09%
15 eggs 1/32,768 .003%
20 eggs 1/1,048,576 .00009%
25 eggs 1/33,554,432 .000003%
I'm not sure where the community wants to draw the line, but things are looking good after 15 eggs if you ask me. To sum it up, it takes a lot of time, resources, and good record keeping to prove a single gene to be dominant.

If the unproven dominant gene is part of a complex, it can easily be proven by breeding two of the same complex morphs together. For example Daddy Gene is part of the same complex as Lesser Platinum. A Daddy Gene and Lesser Platinum sitting together makes a Platinum. Breed two Platinums togther and your left with straight forward odds 25% BEL, 50% Platinum, and 25% Homozygous Daddy Gene. Each of them are entirely different looking morphs, BEL being an all white snake with blue eyes, Platinums looking like hypo Lesser Platinum, and homozygous Daddy Gene looking just like the heterozygous Daddy Gene. All you have to do is hit that 25% chance and it makes it easy to say that the Daddy Gene is dominant.

however the spider gene is a mystery....

http://www.owalreptiles.com/spider.php

The Homozygous Spider

If the Spider is a dominant gene and I bred a Spider with another Spider, I should statistically get 25% Homozygous Spider, 50% Heterozygous Spider, 25% Normal. The homozygous Spider should look exactly like a heterozygous Spider. The only difference would be that the homozygous Spider, when bred to any other ball python, would result in offspring that are all Spiders. While the heterozygous Spider would result in offspring that would only have a 50% chance for getting the Spider gene.

Now here's the problem, the Spider was first established at NERD in 1999, and we still have yet to see a proven homozygous Spider. Now before we get into all the theories, Kevin (the owner of NERD), the guy that imported the first, and has dealt with, more Spiders than anyone else, has to say about the issue. Kevin said that he has not produced and does not believe that there is a homozygous Spider nor that Spider is homozygous lethal. From what I understand he is saying it just simply does not exist for an unknown reason and is not a simple dominant gene.

Another theory is that homozygous Spider is lethal, which is based on the fact that we haven't seen one yet. Which is a pretty weak theory in my opinion, but not entirely dismissible. I do think this theory could be put to rest by watching some Spider x Spider pairing and keeping an eye on the follicles of the females, if somewhere around 25% of them die/reabsorb/not hatch, it may strengthen this theory, but I think people would want to see a lot of eggs before we call it fact. This would be a lot of resources to waste for a big breeder to try, so don't expect it any time soon. I think the only chance of proving this, is by us small breeders trying it out and all of us putting our data together.

Another theory, there hasn't been enough Spider x Spider breedings to prove or disprove a homozygous Spider. Well here's the deal with that, you first have a breed a Spider x Spider. Every Spider offspring only has a 33% chance to be homozygous, then you have to raise up the offspring and do multiple breedings to prove it is in fact homozygous, rather than just getting really lucky on a clutch. So, yes very difficult to prove.

Not many people have the resources to do this, NERD has tired to prove it but as far as I know, they don't have any public statement about what they did to try to prove the homozygous Spider. That leaves this theory open ended. More info would sway my opinion one way or another. Though if Kevin said he did enough breedings, he most likely did enough breedings.

Now the question, "If I bred a Spider x Spider, statistically what % of Spider should I get?" Well If homozygous Spider does exist and is dodging us all these years, 25% homozygous,50% heterozygous, and 25% normal. If it's homozygous lethal then 66% heterozygous and 33% normal. If it doesn't exist for some reason, depending on how you look at it, it could either be 66% heterozygous and 33% normal or 75% heterozygous and 25% normal. So go ahead, pick one.

since I wrote that, someone has released this information... http://ball-pythons.net/forums/showt...98#post1847606

still waiting on a follow up to those results, but it is very interesting.

Soo my question for the day..
Lets say spiders:
After reading the last few days my curiosity was suddenly sparked regarding "super" doms.

Due to them being homo they should in theory throw no normals correct? Yes
As both alleles would throw the spider gene regardless.

I rarely see homo animals advertised, is there a reason for this? Extremely difficult and time consuming to prove out for an animal that looks exactly the same as the heterozygous version, the only advantage would obviously be for breeding.
Is there a price difference?? Never seen one for sale

Het dom to het dom would throw 25pct homos, thus proving would be needed of course.. For the visuals.. yup

Thoughts?? Or am i asking a totally newbie question

Thanks for the time.