Genetics....

[jdhutton2000]

So have been doing a lot of reading and studying on genetics due to the Dom, Co-Dom, Recessive terms thrown around with the occasional Allele and Locus thrown in there.. So in trying to further my understanding of what I am seeing in breeding I am starting to believe there are some truths misrepresented. The first one would be our labeling of dominant genes. Dominant gene would mean that anything on the same locus and the corresponding allele would be overridden by the dominant gene. We have called Spider and Pinstripe dominant genes, when in reality they may be dominant to some alleles but they are in fact incomplete dominant, hence the spinner that comes from the mixing of the two. Also, Co-Dominance means that there will be evidence of the individual alleles present in the resulted phenotype, for example if Mojave and Cinnamon were true Co-Dom you would see part Mojave and part cinnamon on the same snake (which from study sounds a lot like paradox but I am not even going there), instead we once again see incomplete dominance because the result in most of our breeding shows a mixing of different alleles that are not distinctive of the originals. I am not saying I have this 100% down, because I surely don't but I think based on what I read you could refer to Mojave as an incomplete dominant gene with most other allelic combinations and co-dom is mostly in reference to genes like Spider/pinstripe, but in truth these alleles lie on different parts of the genes or possibly another place on the DNA strand all together... and fire away and bash me!!! lol

[Daigga]

No bashing, you just have some terms a little confused.

To relate it to human genetics; a widow's peak is a dominant trait. Like the spider and pinstripe genes, which are generally going to be heterozygous dominant (Ss or Pp), if you were to cross two individuals, one with the dominant trait and one without, half the offspring will be born with and the other half without. The mixing of patterns you get from a spinner combo are more difficult to explain, since you can't really relate snake patterns to human genetics. Patterns just kind of end up mixed when you have more than one present.

Co-doms, or incomplete dominant is the term we use when a trait is expressed visually one way in the heterozygous form, but completely different in the homozygous form. There is no part-mixing when different co-doms are mixed, if you were to mix a mojave and a cinnamon, both would be equally expressed. With color morphs like this, think skin color; if you have a black parent and a white parent, you don't get patchy kids, do you? They end up somewhere in between.

Imperfect metaphors, since in the end ball pythons genetics are very different than humans, but do you kind of see what I mean? It can be a little confusing as far as technical terms go, since most of the terminology used was established by breeders and not geneticists. Just wait until you get into a debate on what "sex-linked" means in ball python breeding.

[OhhWatALoser]

Short answer is yes the hobby has many terms screwed up

The first one would be our labeling of dominant genes. Dominant gene would mean that anything on the same locus and the corresponding allele would be overridden by the dominant gene. We have called Spider and Pinstripe dominant genes, when in reality they may be dominant to some alleles but they are in fact incomplete dominant, hence the spinner that comes from the mixing of the two.

When we call classify a gene we are comparing it to the wild trait allele. Dominant means the phenotype looks the same in heterozygous and homozygous form. So a pinstripe and a super pinstripe (super being another made up term for the hobby) look the same. Spider and Pinstripe are incomplete dominant to each other and could be possibly recessive to other traits. We classify only based on the wild trait allele. Since there is no evidence of a homozygous spider, we really can't classify it. I made up the term "unproven dominant" to cover these traits with unknown homozygous forms.

Also, Co-Dominance means that there will be evidence of the individual alleles present in the resulted phenotype, for example if Mojave and Cinnamon were true Co-Dom you would see part Mojave and part cinnamon on the same snake (which from study sounds a lot like paradox but I am not even going there), instead we once again see incomplete dominance because the result in most of our breeding shows a mixing of different alleles that are not distinctive of the originals.

That is correct. The only gene I know of that could be classified as truly co-dom is scaleless head/scaleless. Everything else as far as i can see would be inc-dom.

[aalomon]

Spider and Pinstripe are incomplete dominant to each other and could be possibly recessive to other traits.

Visually, yes, but not quite genetically. Terms like dominant/recessive/codom/incomplete...are relative terms. They only apply to other genes on the same locus, not to genes in other positions on the chromosome. For example, you can use these terms when comparing to the mojave allele to wild type, lesser, butter...but not spider or albino because spider and albino are in different areas.

The OP was close:
"Dominant gene would mean that anything on the same locus and the corresponding allele would be overridden by the dominant gene [True]. We have called Spider and Pinstripe dominant genes, when in reality they may be dominant to some alleles but they are in fact incomplete dominant, hence the spinner that comes from the mixing of the two[NO]."

Like the first part says, dominant refers to alleles on the same locus but because pinstripe and spider are not their genetic definition does not change.

[jdhutton2000]

Thanks for the replies... Now for a follow on: When Drawing out a Punnett square that is just a statistical tool used to show the distribution of genotypes NOT phenotypes, correct? for example: Take Champagne (C) mixed with Fire (F) and Enchi (E) . Now most people who have messed with the Champ gene know it drowns out most everything, which to me makes it pretty close to a true dominant as I have been able to find; but at the very least an incomplete dominant. So mixing a CF will result in a phenotype of a C however with Enchi the CE is very apparent because those two are VERY Co-Dominant. With that said does this mean that there is a hierarchy of alleles that express themselves over others/with others/almost move to recessive status? Because in my mind as 5+ gene snakes come out, a simple gene like Yellow Belly (still an awesome gene!!) will disappear and once in a blue moon reappear almost making one thing there is a recessive gene and YB will become het Ivory? I think right now we can categorize all these visual heterozygous genes because ball pythons have been relatively untouched for millennia's, but in the next 20-30 years will we be able to?

[aalomon]

Thanks for the replies... Now for a follow on: When Drawing out a Punnett square that is just a statistical tool used to show the distribution of genotypes NOT phenotypes, correct? for example: Take Champagne (C) mixed with Fire (F) and Enchi (E) . Now most people who have messed with the Champ gene know it drowns out most everything, which to me makes it pretty close to a true dominant as I have been able to find; but at the very least an incomplete dominant. So mixing a CF will result in a phenotype of a C however with Enchi the CE is very apparent because those two are VERY Co-Dominant. With that said does this mean that there is a hierarchy of alleles that express themselves over others/with others/almost move to recessive status? Because in my mind as 5+ gene snakes come out, a simple gene like Yellow Belly (still an awesome gene!!) will disappear and once in a blue moon reappear almost making one thing there is a recessive gene and YB will become het Ivory? I think right now we can categorize all these visual heterozygous genes because ball pythons have been relatively untouched for millennia's, but in the next 20-30 years will we be able to?

NO. You are still thinking that every gene possible in the animal relates to every other gene in terms of dominant/codom/recessive...they dont. Those terms only apply to alleles on the same locus. So far champagne is only incomplete dominant (because there is a super, just lethal) with the wild type allele because that is currently the only other allele we know of on the same locus. You cannot compare champagne's incomplete dominantness to any other incomplete dominant gene we know of because they are ALL on other loci.

[Family Jewels]

Co-Dominance means that there will be evidence of the individual alleles present in the resulted phenotype, for example if Mojave and Cinnamon were true Co-Dom you would see part Mojave and part cinnamon on the same snake

I think the first thing to understand about ball pythons genetics is that we use the term co-dominance incorrectly. To date, there is no such thing as a "co-dominant" morph in ball pythons. Period. Everything that we call co-dominant is actually "incomplete dominant" but the other term is used so commonly that we're sort of stuck with it. So you can completely disregard any confusion you have about the true definition of co-dominance not matching ball python genetics. Read the first sentence of the description of Mojaves: http://www.worldofballpythons.com/morphs/mojave/

http://reptilesbreedingenterprise.com/Genetics_3.html

http://www.newenglandreptile.com/ind...dominant-genes
Besides, co-dominance requires two fully dominant alleles expressing themselves at the same locus. Even if we were using the term correctly, Mojave and Cinnamon are found at different loci, so they cannot be described as co-dominant to each other, or even incompletely dominant to each other.

For example:

Lets say the Mojave allele is represented by M, and the normal allele at the same locus is represented by m. Incomplete dominance simply means that the Mm doesn't look exactly like MM or mm. There is a super mojave, a mojave, and a normal... meaning two M's is more phenotypically intense than just one M (hence the term incomplete dominance).

With the Cinnamon trait, the heterozygous cinnamon (Cc) looks different from either the super (CC) or the normal (cc).

Meanwhile, a Mojave Cinnamon would be MmCc, not MC. Mojave is incomplete dominant, and Cinnamon is incomplete dominant, but they are not incomplete dominant to each other. This is called independent assortment and it is crucial to understanding combo morphs.

[OhhWatALoser]

To date, there is no such thing as a "co-dominant" morph in ball pythons. Period.

Why would scaleless head/scaleless not fall under this definition?

[paulh]

Definitions of codominance and incomplete dominance.

I've looked through a number of genetics texts trying to get the lowdown on codominance and incomplete dominance. So far, I have found three different definitions:
1. Position in the AA to aa appearance range. Two genes (A and a) produce three genotypes, AA, Aa, and aa. In incomplete dominance, an Aa individual has an appearance that is more or less intermediate between the appearances of the AA and aa individuals. Example -- red, pink and white flowers. In codominance, the Aa individual has both the AA and aa appearance. Example -- A, B and AB blood types in the ABO blood type system. (By the way, this definition has a third class. Overdominance, where the Aa individual's appearance is outside the AA to aa range.)

2. Number of functional gene products. Two genes (A and a) produce three genotypes, AA, Aa, and aa. In incomplete dominance, only the A gene produces a functional product . The Aa individual produces less product than an AA individual. This causes an Aa individual to have an appearance that is more or less intermediate between the appearances of the AA and aa individuals. Example -- red, pink and white flowers. In codominance, both genes produce a functional product. The Aa individual has both products and both the AA and aa appearance. Example -- A, B and AB blood types in the ABO blood type system. Overdominance is incorporated into codominance.

3. Lumping definition. Two genes (A and a) produce three genotypes, AA, Aa, and aa. Each genotype produces a distinctive appearance. Codominance is the preferred term. Both incomplete dominance and overdominance are synonyms. Examples -- red, pink and white flowers. A, B and AB blood types in the ABO blood type system.

I prefer definition 3 because the other two do not agree. And just changing the test can change the classification.

For example, in humans there is normal hemoglobin and sickle cell hemoglobin. Using definition 1, when a blood smear is examined under the microscope, normal hemoglobin (aa) produces few or no sickled red blood cells. AA hemoglobin produces many sickled red blood cells, while Aa hemoglobin produces an intermediate number of sickled red blood cells. Therefore sickle cell gene is incompletely dominant to the normal gene. However, protein electrophoresis can separate the two hemoglobins, which makes the sickle cell gene a codominant by both definition 1 and 2. The sickle cell gene is an overdominant, too. Because the average life span of an Aa individual is considerably longer than the average life spans of AA and aa humans where malaria is common and medical treatment is poor.

Another example. Siamese cats have two Siamese coat color genes, and Burmese cats have two Burmese coat color genes. The Tokinese cat has a gene pair made up of a Burmese gene and a Siamese gene. The Tonkinese coat color is intermediate between the Burmese and Siamese coat colors. But both genes have a functional product, making them codominant to each other.

Now let's take the mojave gene. A super mojave has some pigment on the top of the head and neck. A super lesser has no pigment on the top of the head and neck. So apparantly the mojave gene is doing something functional even if greatly impaired compared to the normal gene. That would make the mojave gene an incomplete dominant (to the normal gene) by definition 1 and a codominant to the normal gene by definition 2.

For what it's worth, it is hard enough teaching the difference between dominant, codominant and recessive genes. Adding the hassle with incomplete dominant and overdominant just isn't worth it, IMO. Especially as many would simplify things by classing everything as an incomplete dominant. So it's definition 3 for me.

[paulh]

Thanks for the replies... Now for a follow on: When Drawing out a Punnett square that is just a statistical tool used to show the distribution of genotypes NOT phenotypes, correct? for example: Take Champagne (C) mixed with Fire (F) and Enchi (E) . Now most people who have messed with the Champ gene know it drowns out most everything, which to me makes it pretty close to a true dominant as I have been able to find; but at the very least an incomplete dominant. So mixing a CF will result in a phenotype of a C however with Enchi the CE is very apparent because those two are VERY Co-Dominant. With that said does this mean that there is a hierarchy of alleles that express themselves over others/with others/almost move to recessive status? Because in my mind as 5+ gene snakes come out, a simple gene like Yellow Belly (still an awesome gene!!) will disappear and once in a blue moon reappear almost making one thing there is a recessive gene and YB will become het Ivory? I think right now we can categorize all these visual heterozygous genes because ball pythons have been relatively untouched for millennia's, but in the next 20-30 years will we be able to?

Yes. A Punnett square is just a statistical tool used to show the distribution of genotypes NOT phenotypes. Phenotypes are only derived from the genotypes.

You are getting into epistasis with the rest of this post.

New word. Epistasis = A mutant gene at one locus masks the effect of a mutant gene at another locus. Example. In the house mouse, the albino (c) mutant gene prevents melanin from forming. The nonagouti (a) mutant gene changes the normal agouti color to black. The c mutant gene is epistatic to the a mutant gene because a cc mouse and an aa cc mouse look identical -- both are albino; the effect of the a gene is not apparent.