Hi Paul,



First, thanks for bearing with me on this thread, I appreciate you patience and understanding. I think I now see where both sides are coming from. Please see below and let me know what you think:



Paul wrote

>No, this is not correct. Salmon cannot be called a recessive mutant gene because neither a homozygous salmon nor a heterozygous salmon looks normal. If salmon was a recessive mutant gene, heterozygous salmons would look normal.



As salmon is not a recessive mutant gene, it must be some form of dominant mutant gene, where in this case dominant means not recessive. That gives us two choices: dominant or codominant. There seems to be enough overlap of the phenotypes of heterozygous salmons and homozygous salmons to make "dominant" a better choice than "codominant". Go to page 2 of the genetics primer on www.boagenetics.com for a breakdown of how phenotype and genotype determine the classification of dominant, codominant, and recessive mutant genes. <



I agree that the salmon trait is not a recessive trait. The point I was trying to make is that according to Jason's theory there is a distinct, albeit subtle, difference between a salmon {Sa/sa for the sake of argument} and a super salmon {sa/sa} that would qualify it as a codominant trait. As I understand the definition of codominance (and I'm making some pretty broad strokes with my paintbrush here)a trait is codominant when it does not exhibit normal dominance/recessiveness and there is a phenotypical difference between all three possible allele pairs (instead of the normal two we would expect). I meant the super salmon {sa/sa} when I referred to the homozygous recessive phenotype as it applies to codominance, not in the normal dominant/recessive phenotypes.





>You may be right. But other things that might account for the varying degrees of expression include other genes and environment.



I'm not familiar with the term "haploinsufficiency", and I couldn't find it on www.dictionary.com. For what it's worth, molecular functionality does not have a one to one correlation to whether a mutant is dominant, codominant, or recessive. Albino is a recessive mutant gene with a product that is probably nonfunctional. Is albino also haploinsufficient? And after herpers tried to turn "dominant" into a synonym for "homozygous", I'm scared of giving them any new words to misuse. So at this time, I think there are good reasons not to try to replace "codominant" with "haploinsufficient".<



Here is part of the email sent to me by my friend at UMassMed Lab that I mentioned earlier:

"Haploinsufficiency is just a particular kind of codominace, in which one allele is a loss of function, and the het has an intermediate phenotype, because an animal with one allele of the dominant allele (which is usually the wild-type allele) has a different phenotype from an animal with two. One allele is insufficient to give a full wild-type phenotype, hence the

term haploinsufficient."



I concur about giving the herp community at large a new word to throw around. I'm reminded of what the leopard gecko folks did with the patternless/leucistic terminology. I wrote that here in the belief that we could talk about it a level that would help clarify things for me..



>The breeding data in Rich Ihle's paper in the Journal of Heredity proves that salmon can't be a recessive mutant gene. So it has to be some kind of dominant mutant. With "dominant" meaning "non-recessive" here. <

I concur with you. I just question whether dominant is the appropriate term or not(or codominance for that matter)



Later Paul wrote:

Rich has the results of heterozygous salmon x heterozygous salmon matings in his JoH paper. I don't recall numbers, but some normals were born. The expected genotypes would be 1/4 homozygous salmon, 2/4 heterozygous salmon, 1/4 normal. Rich made one homozygous salmon x normal mating, and all the babies were heterozygous salmons, as expected. He also made one heterozygous salmon x homozygous salmon mating, and all the babies were either homozygous salmons or heterozygous salmons, as expected.



The main thing I question is whether Rich's separation of heterozygous and homozygous salmons is 95% or greater correct. And that would require a lot more breeding tests.



Thanks that helps answer a few things. Perhaps by now, Rich has done more breeding with this trait and his next article may help clarify that a bit.



I think ultimately we are talking about exactly the same mode of expression, just choosing to call it different things based on our own philosophies. Much as the Taxonomists tend do (the lumpers and sorters as we used to call them in my zoology and botony labs in college).



>The frequency of a gene in the wild mostly depends on how long ago the mutation occurred and whether it is beneficial or not. Mutants that are some sort of dominants tend to be lost from the population if they are even a little deleterious. Because there is no reservoir of normal-seeming heterozygotes to keep the mutant gene around.<



Such is the case of striping in Pitouphis as I recall, the dominant form is the stripe but it is the less commonly seen form due to environmental influences. Perhaps it was in Lampropeltis getulus californiae. I've forgotten which it was now.



In any case, I think I understand your point of view, now and I do appreciate you hanging around long enough to pound it into my thick skull. I think ultimately we'll have to see what Rich's paper says and I'll wait to start up my test crossing to see what comes out of it.



Thanks again,



Ian Bevan

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