The codominance myth

[CH2O2]

So we have established that "co-dom" is not technically correct and but has been socially accepted as simple way to describe BP genetics.

That pretty much sums it up.

[jbean7916]

So your conclusion is that breeders wont learn 5 definitions because they are either lazy or ignorant. I don't believe that. I believe people that do know and understand the definitions are unwilling to teach them.

why do you insist that everyone is ignorant or lazy? Ours is not the first group of people to adapt a word into a different meaning.

even in the English language there are words that have different definitions in different locations.

Take the word boot for example. In my house, boot can mean a couple things: footwear or the process of loading an OS like on a computer. Skip on across the atlantic and they'll tell you its on the back of a car. I could argue until I'm blue in the face that it's not a "boot" they are referring to, but a "trunk". But, both words are acceptable to define that space, its a matter of the group of people you are with.

We have "redefined" codom for our own needs and it has suited us well. Why are you making it your personal crusade to correct everyone?



sent from my EVO

[Method919]

I personally think that using the breeding of ball python morphs as a tool for teaching the basics of genetics and biology is one of it's strongest redeeming factors. Indeed it may be one of the best arguments for fighting the legislation going on right now; that keeping and breeding reptiles is a great way to get people interested in science.

That being said, I think it's absurd people are really trying to stifle conversation about this or claim that it's perfectly OK for the entire industry to be wrong about some of the basic terminology involved. If you're not interested in the genetics, fine, you don't need to talk about it, but certainly don't come in here and say that it shouldn't be addressed because it's easier or more convenient for 'the industry'.

The more people know about the genetics, in my opinion, the more interesting it all becomes. It would also really give the breeders a better understanding of what they're doing, which I would assume would be fairly important for the people out there with tens of thousands of dollars invested in this. For example, when I hear people talking about trying to 'fix' problems associated with morphs, but they have no idea what the genetic basis of doing such a thing would entail, it makes me cringe. Anyways, just thought I'd throw in my opinion, keep the genetics talk comin' and if you don't want to talk about it then move to another thread!

[paulh]

Can you please show me a biochemical definition of codominant and incomplete dominant? Are you saying that by using such a definition, a pastel snake would be correctly classified codominant insted of incomplete dominant?

There are two genes, A and a. The A gene may be the wild type gene, and the a gene may be a mutant gene. Or the A gene may be a mutant gene, and the a gene may be the wild type gene. Or the A and a genes may be different mutant genes. The A gene and the a gene can form three gene pairs, AA, Aa, and aa.

Incomplete dominant genes:
1. Phenotype definition. The AA genotype produces the AA phenotype. The Aa genotype produces the Aa phenotype. And the aa genotype produces the aa phenotype. All three genotypes can be inferred from the phenotypes. AND the Aa phenotype is more or less intermediate between the AA and aa phenotypes.
2. Molecular genetics definition. The AA genotype produces the AA phenotype. The Aa genotype produces the Aa phenotype. And the aa genotype produces the aa phenotype. All three genotypes can be inferred from the phenotypes. AND one gene produces a functional enzyme or other product while the other gene produces a nonfunctional product.

Codominant genes (narrow classification):
1. Phenotype definition. The AA genotype produces the AA phenotype. The Aa genotype produces the Aa phenotype. And the aa genotype produces the aa phenotype. All three genotypes can be inferred from the phenotypes. AND the contribution of both the A gene and the a gene can be detected in the Aa phenotype.
2. Molecular genetics definition. The AA genotype produces the AA phenotype. The Aa genotype produces the Aa phenotype. And the aa genotype produces the aa phenotype. All three genotypes can be inferred from the phenotypes. AND both genes produce functional products.

Sources for the molecular genetics definitions:
Knight, Jeffrey A. and Robert McClenaghan. Encyclopedia of Genetics. Salem Press, Pasadena, California, USA, 1999. 2 vols.
Zubay, Geoffrey. 1987. Genetics. The Benjamin/Cummings Publishing Co., Menlo Park, CA. 1987, 973 pp. ISBN 0-8053-09100-3

As far as I know, the biochemistry of the pastel mutant gene has not been worked out. But here is one way it could work.

The pastel mutant gene could produce a functional product but a different amount of it than the normal gene (which also produces a functional product). Total the amounts produced from two normal genes, from a pastel and a normal gene, and two pastel genes. A pastel and a normal gene produce less than two normal genes, and the pastel royal is lighter than a normal. Two pastel genes produce the least, and the super pastel royal is lightest of all. That is the way the burmese and siamese genes work in cats. The homozygous burmese cat is the darkest, the homozygous siamese is the lightest, and the tonkinese cat (with a burmese gene paired with a siamese gene) is roughly intermediate between the other two.

I will not venture to speculate on motives. But it took my breath away the first time someone told me that the following definitions of homozygous and heterozygous were too complicated to learn.

Homozygous = the two genes in a gene pair are the same.
Heterozygous = the two genes in a gene pair are NOT the same.

[CH2O2]

why do you insist that everyone is ignorant or lazy?

I do not. If you read carefuly you will see i stated exactly the oposite.

Ours is not the first group of people to adapt a word into a different meaning.
even in the English language there are words that have different definitions in different locations.

We are not talking about the english language. We are talking about the language of science. The language of science needs to be clear and inequivocal or it stops beeing the language of science to become something else.

Why are you making it your personal crusade to correct everyone?

I am not. Everyone is free to use the incorrect terminology. What i can't understand is WHY someone would want to be incorrect.

[CH2O2]

There are two genes, A and a. The A gene may be the wild type gene, and the a gene may be a mutant gene. Or the A gene may be a mutant gene, and the a gene may be the wild type gene. Or the A and a genes may be different mutant genes. The A gene and the a gene can form three gene pairs, AA, Aa, and aa.

Incomplete dominant genes:
1. Phenotype definition. The AA genotype produces the AA phenotype. The Aa genotype produces the Aa phenotype. And the aa genotype produces the aa phenotype. All three genotypes can be inferred from the phenotypes. AND the Aa phenotype is more or less intermediate between the AA and aa phenotypes.
2. Molecular genetics definition. The AA genotype produces the AA phenotype. The Aa genotype produces the Aa phenotype. And the aa genotype produces the aa phenotype. All three genotypes can be inferred from the phenotypes. AND one gene produces a functional enzyme or other product while the other gene produces a nonfunctional product.

Codominant genes (narrow classification):
1. Phenotype definition. The AA genotype produces the AA phenotype. The Aa genotype produces the Aa phenotype. And the aa genotype produces the aa phenotype. All three genotypes can be inferred from the phenotypes. AND the contribution of both the A gene and the a gene can be detected in the Aa phenotype.
2. Molecular genetics definition. The AA genotype produces the AA phenotype. The Aa genotype produces the Aa phenotype. And the aa genotype produces the aa phenotype. All three genotypes can be inferred from the phenotypes. AND both genes produce functional products.

Sources for the molecular genetics definitions:
Knight, Jeffrey A. and Robert McClenaghan. Encyclopedia of Genetics. Salem Press, Pasadena, California, USA, 1999. 2 vols.
Zubay, Geoffrey. 1987. Genetics. The Benjamin/Cummings Publishing Co., Menlo Park, CA. 1987, 973 pp. ISBN 0-8053-09100-3

As far as I know, the biochemistry of the pastel mutant gene has not been worked out. But here is one way it could work.

The pastel mutant gene could produce a functional product but a different amount of it than the normal gene (which also produces a functional product). Total the amounts produced from two normal genes, from a pastel and a normal gene, and two pastel genes. A pastel and a normal gene produce less than two normal genes, and the pastel royal is lighter than a normal. Two pastel genes produce the least, and the super pastel royal is lightest of all. That is the way the burmese and siamese genes work in cats. The homozygous burmese cat is the darkest, the homozygous siamese is the lightest, and the tonkinese cat (with a burmese gene paired with a siamese gene) is roughly intermediate between the other two.

I will not venture to speculate on motives. But it took my breath away the first time someone told me that the following definitions of homozygous and heterozygous were too complicated to learn.

Homozygous = the two genes in a gene pair are the same.
Heterozygous = the two genes in a gene pair are NOT the same.

If we use the codominante molecular definition and if the pastel gene is functional (at a lower degree compared to the normal) i would agree to call the morph codominant.

Excelent explanation by the way.

[snake lab]

As i said on page 1. Whats the point? Those of us that breed know what snakes to put together for the outcome we want. So the argument of terminoligy really is irelevant. If i call a pastel codominant or incomplete dominant or if i call it sally isit gonna change the outcome of the offspring?

[OhhWatALoser]

We are not talking about the english language. We are talking about the language of science. The language of science needs to be clear and inequivocal or it stops being the language of science to become something else.

i think he's getting closer to understanding guys.... just wait for it....

I am not. Everyone is free to use the incorrect terminology. What i can't understand is WHY someone would want to be incorrect.

We are in the "something else" As it has been stated and rephrased to you multiple times.

[CH2O2]

i think he's getting closer to understanding guys.... just wait for it....



We are in the "something else" As it has been stated and rephrased to you multiple times.

Like i said, it is your right to be the "something else". But that does not mean it is correct. You can shoot yourself in the head but i would, at least, try to persuade you not to.

[CH2O2]

...this is a sociology issue not a biology one...

I agree. People often reject change. Even when it is for the best.