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I keep seeing that the Salmon trait in Boas is codominant. If this is true, what are the distinguishing characteristics between a salmon and a super salmon. By definition, a codominant trait shows three different phenotypes - 1 for homozygous recessive, one for homozygous dominant, and one for the heterozygous state.

Can someone point out the characteristics? Or better yet post pictures of a salmon and a confirmed Super?

Thanks,

Ian

The salmon or hypo trait is dominant.

I have a theory that it is possible to tell deffinately not supers but not to deffinately distinguish a super hypo.
I have yet to find a picture of a proven super hypo that has a great deal of black pigment on the tail past the vent. Most likely the individuals with little to no black pigment on the tail past the vent will be supers but this is not always true as there are some non supers that have significant reduction of pigment past the vent. I believe this occourance is the cause behind the thought of the gene being co-dominant as opposed to dominant.
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- Jason F.

So, what leads you to believe this is a dominant trait? I've looked all around and that seems to be the consensus but no one seems to be able to say why.

I've run this by an old friend of mine who is the lab director for the University of Massachuesitts Medical School and got his PHD in worm genetics. I included Rich Ihle's article from the journal of heredity along with all the info I had.

His opinion, based on the info at hand, was that this was a codominant trait (in fact it might be more accurately termed haploinsufficiency rather than codominance or incomplete dominance).

So I'm just curious what evidence points to this trait being a dominant one?

Ian

>So, what leads you to believe this is a dominant trait?

For what it's worth, my definition of a codominant is as follows: An untrained person can spend five minutes looking at normals, heterozygotes and mutant homozygotes. After that, he can sort a mixture of 100 snakes into the three genotype categories with at least 95% accuracy.

From the posts on these forums, the breeders can't do anywhere near that well even after a lot of experience.

Salmon isn't a recessive mutant gene because the heterozygotes do not look normal. And it doesn't fit the codominant definition above. By elimination, it's a dominant mutant gene. It doesn't fit the definition of a dominant mutant gene very well; it's in the gray area between "dominant" and "codominant". "Dominant" is simply the best fit, not a perfect fit.

I've been told that Rich Ihle will have an article in Reptiles magazine in a few months. Maybe we'll get better information then.

Paul Hollander

Paul,

So if I understand your reasoning, because the salmon trait appears to not have a distinct visible homozygous recessive phenotype, it cannot be explained as a codominant trait. Is this correct?

I at no time claimed to be able to look at a trait and claim it was dominant, codominant or recessive. If I did, then I apologize. All I am seeking is to understand the genetics behind this trait.

I would argue that the Salmon trait (hypomelanism) is in fact codominant (the more accurate term might be haploinsufficiency). A dominant trait when bred to any other allele always expresses itself. If the salmon trait is dominant and you breed a salmon to a normal appearing b.c.i. then you would expect to see nothing but salmons in the f1 generation, no normals what so ever. Is this the case (I only ask as my salmon male - whom I suspect is a super salmon is too young to breed until next season so I don't know what the outcome would be)? What are the phenotypic ratios one gets in the f1 generation between this breeding? Do any normals appear? If so, then the trait must be codominant (haploinsufficient).

Haploinsufficiency, basically is a loss of function state. Whereby, the loss of function is variable, which could account for the varying degrees of expression seen in the breedings.

I'm just trying to understand what criteria were used to determine that the trait was dominant and what the test results were that bear that out.

Thanks,

Ian

I think you are a bit confused about genetics. First I would like to say I agree with what Paul said.

Second, you said that in order for the hypo gene to be dominant all the offspring of a normal to hypo breeding would be hypo. This is only true in the case of a homozygous hypo.

Each animal has two sets of genes and each gene has the equal chance of being passed onto the offspring. In the case of a heterozygous for a dominant gene animal (lets say it is a hypo) bred to a normal animal the litter would theoretically have split genetics/phenotype(appearance). Since the hypo has not only a hypo gene but also a normal gene that both have a 50% chance of being passed to its offspring (each baby has the same 50/50 chance) the litter will in a perfect world be half hypo and half normal.

Co-dominant is characterised by two distinct phenotypes(appearances) caused by one gene. In boas the best example is the motley gene. The heterozygous form looks distinclty different from the wild type as well as from the homozygous form.

I think the problem is that the hypo gene is not a pattern mutation but rather a color mutation, so it is not as easily visible. Additionally the gene does not systematically decrease pigment because if it did a homozygous animal would always have less black pigment then a heterozygous animal. This is disproven by proven/known heterozygous animals who have extreme reduction of black pigment (hypo pastels further complicate things).

I feel that it is only possible to visually determine that an hypo is not a homozygous hypo. In my eyes this is done by examining the black pigment on the tail after the vent. Although some heterozygous animals have extreme reduction in black pigment in this area, I have yet to see a proven or known homozygous hypo that does not have significant reuction of black pigment in this area (retains that dark black rings around tail blotches after the vent).

This is my feelings on the matter, and I intend to attempt to expreiment on my theory concerning the hypo gene.
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- Jason F.

Jason,

You are correct in that I failed to clarify the P1 generation. Assuming that you are starting with a homozygous recessive sire bred to a homozygous dominant dam, your expected outcome would be all heterozygotes. Assuming a hetero to hetero breeding you would expect 1:2:1 (roughly) breakdown in phenotypes. Hetero to homozygous dominant would yield as you said a 50:50 mix of offspring (roughly).

You state that you "feel it is only possible to visually determine tha an hypo is not a homozygous hypo." Thus you are indicating that there is a distinct phenotypical difference between the homozygous dominant, heterozygous, and homozygous recessive state. Which is the definition of a codominant trait.

I guess we are going to have to agree to disagree on this one until we can prove out our test crosses. Coloration is a multiallelic trait and can be effected by so many different factors that we may never sort it out.

I'm just curious what the the phenotype breakdowns have been on the various states. What were the results of a hetero to homozygous dominant? What were the results of a hetero to hetero breeding?

As I mentioned, I'm just trying to understand the position that this is a dominant trait. If it were, you would expect to see it more often in wild populations than in the rare instances that it does occur.

Ian

One point that is not being understood clearly that while SOME maybe even MOST Homozygous Salmons have significantly reduced Black around the post tail blotches, this is NOT a foolproof method for determining Homozygous offspring. There are Hets that also have this same reduction in black. About the best you could do when sorting is to have a pile with black that are very probably hets and another pile with reduced black that have a higher probability of being homozygous. And that's only due to removing probable hets from the mix. You can never be certain since the probability for 25% Homozygous / 50% heterozogous / 25% Normal form a het x het breeding is just that....probable, we see litters that beat the odds and litters that get beat by the odds.
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Thanks,

Dave "Rainbows-R-Us"

0.1 Wife (WC)
0.2 kids (CBB)
2.7 Brazilian Rainbow Boa (adult breeders)
2.5 Brazilian Rainbow Boa (sub-adult from 2004)
4.8 Brazilian Rainbow Boa (sub-adult from 2005)
2.1 Hypomelanistic BRB
0.1 Het for Hypomelanistic BRB
0.1 BCI "Elvira" normal from 1989
1.0 BCI Albino / het-anery
0.1 BCI Salmon / het-albino
0.1 BCI Anery / het-albino
0.1 BCI Salmon (possible super)
1.0 BCI Albino het stripe
1.0 BCI Salmon
0.1 BCI Ghost
0.1 BCI Super salmon, possible jungle
1.0 BCI Salmon, possible jungle
0.1 BCI Super Ghost

lots.lots.lots feeder mice and rats

Ian wrote:
>So if I understand your reasoning, because the salmon trait appears to not have a distinct visible homozygous recessive phenotype, it cannot be explained as a codominant trait. Is this correct?

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.

>Haploinsufficiency, basically is a loss of function state. Whereby, the loss of function is variable, which could account for the varying degrees of expression seen in the breedings.

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".

>I'm just trying to understand what criteria were used to determine that the trait was dominant and what the test results were that bear that out.

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.

Later Ian wrote:
>I'm just curious what the the phenotype breakdowns have been on the various states. What were the results of a hetero to homozygous dominant? What were the results of a hetero to hetero breeding?

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.

>As I mentioned, I'm just trying to understand the position that this is a dominant trait. If it were, you would expect to see it more often in wild populations than in the rare instances that it does occur.

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.

Paul Hollander

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.

Ian Bevan

Sorry, I'm in a hurry right now so must be brief.

Yes, I think we are getting on the same wavelength.

I agree with what you say about Jason's theory. I'll be interested to find out if it pans out.

Thanks for the bit about haploinsufficiency. I know of several mutants of the sort but was not aware that the molecular guys had tagged the phenomenon with that name.

By the way, using "homozygous mutant phenotype" and "heterozygous mutant phenotype" rather than "homozygous recessive phenotype" when talking about dominant and codominant mutants will reduce misunderstanding.

Paul Hollander

Have you read the papers that Rich Ihle, et al, published? Link is below.

I've only seen a couple of salmons in the flesh, so all I have to go on is those papers and what I see in these forums. Ideally, a codominant mutant should produce a heterozygote with a phenotype that does not overlap the phenotype of either of the two homozygotes. For what it's worth, my opinion is that when looking for the homozygous salmons, Rich picked out the snakes that were most different from normal. And he didn't test enough snakes that were in the range where the phenotype of the heterozygous salmon overlaps the phenotype of the homozygous salmon.

In other words, the classification of salmon as a codominant mutant gene is partly an artifact of breeder selection.

I've been told that Rich will have an article about salmon in Reptiles Magazine in a few months. Maybe there will be more information in there.

Paul Hollander
salmon articles