Why I think we need unproven dominant

[OhhWatALoser]

So some resent threads have made me want to comment on some things on classifications and I realize this ties into something I wish to catch on, so here it is all in one....

The Basics

With out even talking about classifications, we need to go over some things. Genes come in pairs in snakes. The location a pair of genes sits at is called a locus. You can see this illustrated in judy's guide. There are two terms I am going to be using a lot and for some reason they seem to be over looked by most of the community. That is heterozygous and homozygous.

Heterozygous (het) simply means the pair of genes are not the same.
Homozygous (homo) simply means the pair of genes are both the same.

In a normal ball python, we do not identify any mutant genes, so we just call them normal. Anything we call a morph has a mutant gene. If the genes are the same, mutant or not they are homozygous. If they are not the same. it is heterozygous.

ex.
Pastel: Heterozygous (one pastel, one normal)
Super Pastel: Homozygous (two pastel)
Het Albino: Heterozygous (one albino, one normal)
Albino: Homozygous (two albino)

Easy right?

Genetic Classification

Now that we can identify a mutant gene in heterozygous or homozygous form, we can now classify it. Classifications are based of how the snake looks in heterozygous (mutant gene + normal) and homozygous (two of the same mutant gene) This is how simple it really is:

	Heterozygous	Homozygous
Dominant	Visual	Same Visual
Co-Dom/Inc-Dom	Visual	Different Visual
Recessive	Not Visual	Visual

Now before you start the whole "What we call Co-Dom is really Inc-Dom!", it is true both in heterozygous form are visual and both in homozygous form have a different visual. If thrown under the same heading, the difference between them does not matter for this discussion.

So that is how simple it really is. A Dominant gene looks the same whether there is one mutant gene or two. Co-Dom/Inc-Dom look different from normal in heterozygous, (ex. Yellow Belly) and homozygous has another different look. (ex. Ivory). Recessives look the same as a normal in heterozygous and only visually show in homozygous (ex. Albino).

Now what really seems to be misunderstood is what a dominant gene is, it is as simple as looking the same in heterozygous and homozygous.

It does not mean anything magical happens when they breed together. Genetic classification doesn't change anything. It is just a classification after all. The genes really don't care what you call them.
It does not mean there is no "super" for some magical reason. To be called dominant the "super" must look like the heterozygous.
It does not mean the super is lethal. If the gene is homozygous lethal, that would mean it is Co-Do/Inc-Dom since, dead is a different visual than, the alive heterozygous.

Unproven Dominant

Up until now two scenarios have been lumped together and called dominant. I believe this as caused a lot of confusion and these two scenarios really need to be separated. this is how things are currently:

	Heterozygous	Homozygous
Dominant	Visual	Same Visual
Dominant	Visual	??????

Right now, we classify true dominant genes the exact same, as genes we have never even seen or have any sort of proof of the homozygous. We just throw them into "Dominant until proven otherwise". Which worked for a while when there wasn't any true dominant genes widely known, but all it really means is "we know it's not recessive." But this also seems to have fed rumors or magical thing happening when they breed, supers not existing for some magical reason, or just being lethal. Basically a whole misunderstanding of what a genetic classification is. So this is why I think we need to separate these two scenarios.

	Heterozygous	Homozygous
Dominant	Visual	Same Visual
Unproven Dominant	Visual	?????

I believe this to be a more accurate, as we have the real definition of dominant and we accurately describe the genes that have an unknown homozygous. They are not proven to be dominant yet.

Proving a Gene Dominant

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. It is actually the exact same process, if you bred two het albinos together and tired to prove one of the normal looking babies to truly be normal.

When we have different mutant genes that sit on the same locus, we say they are part of the same complex. 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.

Known Dominant Morphs

Pinstripe - was proven at bhb, his records show the exact scenario above with 27 eggs all being pinstripes
Daddy Gene - RDR has it in his online records that he bred a platty to a platty and produced a het daddy looking snake. clutch 76
Congo - Vin Russo stated on his old website that the congo he imported was homozygous and produced all congos, while the offspring were able to produce normals and congos. His website is now being redone and I don't see where he has but that information back up.

Why Not More?

Read about all the work it takes to prove a dominant trait out. The time, money, and females that could be producing something else. Now you spend all that time to create a snake that looks exactly the same as the heterozygous. It really makes zero sense economically to pursue the project, since looks are what sell. Sure it would be a powerhouse breeder, but so is any other homozygous mutation that doesn't require the the time, money, and females. Then you also shrink your potential customer base with people who do not understand what a homozygous dominant trait is. I think most breeders realize this and choose to pursue more exciting projects.

The Spider Ball Python

I figure this would get brought up as it is the most commonly referred to dominant morph. We have not seen the homozygous or anything concrete about it, so I would just call it Unproven Dominant. As far as the other potential issues surrounding it, that's another can of worms and not part of this discussion. Remember the genes don't care what you call them, they work the way they work, whether it fits your definition correctly or not.



So basically I think this is a good way to accurately describe what we are seeing and hopefully reduce the confusion.

	Heterozygous	Homozygous
Dominant	Visual	Same Visual
Unproven Dominant	Visual	?????
Co-Dom/Inc-Dom	Visual	Different Visual
Recessive	Not Visual	Visual

[Mrl249]

Thank you for posting this!

[Pythonfriend]

interesting, not much new for me here, but its interesting to hear that the super pinstripe had been proven out. I believed pinstripe would be like spider, with a mysteriously missing super form.


For me, whats most important above all else when judging a gene is: Does the super-form exist and is it healthy?

not a criticism of your post, but i dont like the guide you linked: http://ball-pythons.net/forums/showt...Basic-Genetics i dont like it, because i consider every single graphic to be a bit misleading. it looks a bit like 2 chromosomes, but two genes hit one chromosome, really strange, but then you realize that the long strands are supposed to be the whole genome of the snake and the little colored circles get distributed, also really strange. In fact chromosomes get distributed, genes like albino always sit on the same chromosome. And each BP has each chromosome 2 times. Heterozygous: the two chromosomes in question are different. Homozygous: the two chromosomes both have the gene in question.

But you did a good job. I wonder if it catches on, or maybe it will evolve into slightly different categories. like: recessive, codominant, nice dominant, problematic/questionable dominant.

[TJ_Burton]

Not a bad read overall.

[OhhWatALoser]

not a criticism of your post, but i dont like the guide you linked: http://ball-pythons.net/forums/showt...Basic-Genetics i dont like it, because i consider every single graphic to be a bit misleading. it looks a bit like 2 chromosomes, but two genes hit one chromosome, really strange, but then you realize that the long strands are supposed to be the whole genome of the snake and the little colored circles get distributed, also really strange. In fact chromosomes get distributed, genes like albino always sit on the same chromosome. And each BP has each chromosome 2 times. Heterozygous: the two chromosomes in question are different. Homozygous: the two chromosomes both have the gene in question.

All it shows that two genes sit together, and the statistics of inheritance. which is about as far as you need to know for this discussion. I also know judy would be more than happy if you made some accurate pictures to replace them.

But you did a good job. I wonder if it catches on, or maybe it will evolve into slightly different categories. like: recessive, codominant, nice dominant, problematic/questionable dominant.

We could go recessive, not recessive, co-dom, and dom?

[mlitz]

Needs to be stickied! good information.

[SaintTawny]

It does not mean the super is lethal. If the gene is homozygous lethal, that would mean it is Co-Do/Inc-Dom since, dead is a different visual than, the alive heterozygous.

This isn't strictly true, when you think about the way that gene codes are repurposed in different areas of the body. Take this imaginary situation for example: Imagine that an egg was produced that was homozygous for the spider gene, but showed no visual difference from the heterozygotes we're all familiar with. We would properly call that a dominant gene. Now if that egg failed to hatch, and others like it were proven to be not viable, but the partially developed embryos showed no visual difference from similarly developed heterozygotes, we could still properly call it a dominant gene. I'm of the opinion that enough evidence exists to prove that the same allele that causes the spider mutation also somehow impairs coordination and causes wobble. This one allele can cause changes in the scale pattern AND a deficiency in some protein at the same time, which would make the two inseparable. We wouldn't call it co-dom/inc-dom if this allowed heterozygotes to survive using their single "normal" allele, but was fatal to homozygotes due to complete lack of production of that necessary protein.

interesting, not much new for me here, but its interesting to hear that the super pinstripe had been proven out. I believed pinstripe would be like spider, with a mysteriously missing super form.


For me, whats most important above all else when judging a gene is: Does the super-form exist and is it healthy?

If we're going to get picky about the use of the term dominant vs. co-dominant, I think we should reserve the word Super for homozygotes of co-dominant genes. The phrase "Super Pinstripe" makes it sound like a super pastel, or super mojave, where there is a visual difference between het and homo.

[OhhWatALoser]

This isn't strictly true, when you think about the way that gene codes are repurposed in different areas of the body. Take this imaginary situation for example: Imagine that an egg was produced that was homozygous for the spider gene, but showed no visual difference from the heterozygotes we're all familiar with. We would properly call that a dominant gene. Now if that egg failed to hatch, and others like it were proven to be not viable, but the partially developed embryos showed no visual difference from similarly developed heterozygotes, we could still properly call it a dominant gene. I'm of the opinion that enough evidence exists to prove that the same allele that causes the spider mutation also somehow impairs coordination and causes wobble. This one allele can cause changes in the scale pattern AND a deficiency in some protein at the same time, which would make the two inseparable. We wouldn't call it co-dom/inc-dom if this allowed heterozygotes to survive using their single "normal" allele, but was fatal to homozygotes due to complete lack of production of that necessary protein.

If we're going to get picky about the use of the term dominant vs. co-dominant, I think we should reserve the word Super for homozygotes of co-dominant genes. The phrase "Super Pinstripe" makes it sound like a super pastel, or super mojave, where there is a visual difference between het and homo.

I am using laymen terms, A dominant trait would actually be defined as showing the same phenotype. A Phenotype is defined as an observable characteristic or trait and basically includes anything not called genotype.

As for the use of the term "super." Most people seem to use it as a snake that does not throw normal offspring.

[TheSnakeGeek]

good post.. although i feel, for the most part, the people who know "co-dom" is really inc dom, know this as well. its all just hobby "jargon" that may mean something different when looked at from a technical standpoint, but others in the hobby still know what you're talking about.

[Royal Hijinx]

Very nice. I think once we get to the .001 that should be good enough to call it homozygous.