Reptile & Amphibian Forums

I am pretty sure this had been brought up, but can someone explain to me why the hypo gene is co-dominent instead of complete dominance?

Not trying to start an argument, it just seems like the herp community often struggles with the basic concepts of genetics, let alone more complicated ones. Reasoning I see here often doesn't correlate what I learn in classes or read in text books.

I have to give my respect to people like Paul for really trying Paul H for trying to bring it to the next level. But are we building on a broken foundation (not you Paul, making a generalization)?

I could be wrong (I certainly do not have my degree in this), but I just wanted to hear some explanations for this!

Thanks!

The traditional Hypomelanistic mutation is a dominant mutation. Salmon and Hypo are synonymous.

Anyway...
Homozygous Hypos (Supers) have the same phenotype as Heterozygous Hypos (Non-supers). This equates to a Dominant mutation.

If the mutation was co-dominant, there would not be "Possible Supers" because we could tell Homozygous Hypos from Heterozygous Hypos.

That is the way I understand it. There is also more to it that I will chime in on later, but wanna see what people say LOL.

Co-dominant by definition is where the heterozygote exhibits the phenotypes of both homozygotes. Now let me try to explain this:
H = normal boa coloration
H* = the co-dominant hypo gene

Now if you cross an animal that is HH to an animal that is HH* then half of your offspring will be hypo and half will be normal. Now the ones that have the HH* will be hypo but they can look from either a really clean red normal or that beautiful thin saddle and no black pigment that everyone loves. Now if you were to cross an animal that was HH* to one that is HH* then your outcome is 1/4 normal, 2/4 possible super hypo and 1/4 super hypo. Now the reason there are possible super hypos is because some HH* snakes can look like super hypo that is H*H*. But some H*H* snakes you will see are just obvious supers because they have almost no saddles and have no black pigment. Therefore the heterozygous snakes that are HH* will show both a look of the HH and the H*H*. This means that this is a co-dominant gene. If it was a complete dominance than you would not see such a difference between hypos and super hypos. A complete dominance would not allow any of the normal coloration to come out in the heterozygous HH* individuals.

Now I am sorry if this is confusing but this is what I have learned in class and in studying this topic in general. If someone thinks I am wrong please show me how.
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1.1 Motley het butter corns
0.1 Snow corn
0.1 Okeetee corn
1.0 Anery mutt corn
0.1 Stripe Ghost corn
0.1 Amelanistic corn het carmel
2.1 Colombian Redtails
1.0 Hypo Colombian redtail
1.0 Brazilian Rainbow Boa
1.0 Anery Kenyan sand boa
0.1 Normal Kenyan sand boa

Others here are better at explaining fine details than I, however I can assure you Hypo is dominant.

In a co-dominant mutation the heterozygous animals have a different phenotype than wild type animals, and homozygous animals have a third phenotype.

In a dominant mutation the heterozygous animals have a different phenotype than wild type animals, and homozygous animals have the same phenotype as the heterozygous animals.

Motley is Co-dominant, Heterizygous form is the Motley, Homozygous form is the Patternless.

Hypo is Dominant, Heterozygous form is Hypo, Homozygous form is Hypo.

No if it was dominant than there would be no difference between the hypos and super hypos and there definetly is. Now there are some that look alike but that is only in very clean hypo individuals. If you look at a hypo, not one that looks overy great, you can still see that normal coloration in part of it. So it could not be dominant and still show the normal coloration.
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1.1 Motley het butter corns
0.1 Snow corn
0.1 Okeetee corn
1.0 Anery mutt corn
0.1 Stripe Ghost corn
0.1 Amelanistic corn het carmel
2.1 Colombian Redtails
1.0 Hypo Colombian redtail
1.0 Brazilian Rainbow Boa
1.0 Anery Kenyan sand boa
0.1 Normal Kenyan sand boa

Many F1 Hypos could pass for Supers, some Supers look worse than many F1 Hypos. If you could tell the difference between Heterozygous and Homozygous Hypos 100% of the time, then you could call it co-dominant.

This is just not the case. If you know some hidden way to pick out Supers and non-Supers in every single Hypo, please share.

It doesn't fit any ideal definition, but by defalt falls back on dominant.

The way that you are explaining it would be incomplete domanance I believe. For example you breed a red flower (super hypo) to a white flower (normal), you will get all pink offspring (reg hypo). If you two pinks together you will get 25% red, 50% pink, 25% white. Does that make sense? What you have is a blending of the phenotype. The initial offspring (from red x white) don't match either parent. I will explain later why I don't feel it is this

The reason why it is not co dominent is because you don't have 2 genes. For example, lets say you had a spotted clover and a tipped clover. When you breed them together the offspring would both tipped and spotted (but not blended between the two) Both traits are fully expressed. Hypomelanism is only one gene.

Does that make sense?

I should have put alleles not genes for the bottom part, sorry...

.
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1.1 Motley het butter corns
0.1 Snow corn
0.1 Okeetee corn
1.0 Anery mutt corn
0.1 Stripe Ghost corn
0.1 Amelanistic corn het carmel
2.1 Colombian Redtails
1.0 Hypo Colombian redtail
1.0 Brazilian Rainbow Boa
1.0 Anery Kenyan sand boa
0.1 Normal Kenyan sand boa

>The reason why it (hypo) is not co dominent is because you don't have 2 genes.

This does not make sense to me. You have salmon (AKA hypo) and normal. Two genes right there.

I consider salmon (AKA hypo) to be a dominant for the same reasons Chris Gilbert gave. Its inheritance pattern puts it on the borderline between dominant and codominant, and in such cases I think the better course is to push the mutant into the "dominant" category.

As to whether to use codominant or incomplete dominant, I've seen several different definitions used to split the two. But all the definitions included that both categories had three phenotypes, one corresponding to AA gene pair, the second to Aa gene pair, and the third to the aa gene pair.

When Mendel originated the terms "dominant" and "recessive", he applied them to a two phenotype situation. The genotypes AA and Aa produced one phenotype, and the genotype aa produced the second phenotype. This was the simplest, broadest possible division for his results.

Genetics texts still use dominant and recessive in the same sense Mendel did. My old genetics prof wanted to make things as simple as possible FOR TEACHING PURPOSES, so he chucked "codominant", "incomplete dominant", "transdominant", "less than fully dominant", etc., etc. Though there are fine differences of meaning, every one of these terms include the concept that there are three phenotypes corresponding to the AA, AA, and aa genotypes. What to call these genes? "Codominant" has the fewest characters, so that is what he used.

In my opinion, these forums are teaching tools. KISS rules. I'm not going to agonize over whether codominant or incomplete dominant is the better term. At the simple level we use here, they are synonyms.

Paul Hollander

The way I see it from many hypos, is that there are some supers that don't have the classic super look.. Sometimes they just look like good old F1 hypos, and depending on what you breed if you pair some really clean animals you could get some that look super but are not.

Thats went to calling F2's and F3's that are not 100% supers possible super and probible super.. possible's price reflects what i think they are and so do probables..

Of course with the first super motleys being born recently no one really knows that some of the classic looking motleys in a littler that produced supers is not in fact a dominant animal.
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Ed Lilley, www.constrictorsnw.com
www.reptileinsider.com

IMO, if the hypo gene was truely codominant, you wouldn't have "possible supers". You would be able to tell one way or the other. I use the tiger mutation in retics as the classic example. You don't hear about "possible super tigers". They either are or they aren't. The other option that I haven't heard is that there could be a second gene linked to the hypo gene such that it was carried around with the hypo gene. This could cause some of the differences we're seeing with some, but not all of the homozygous hypos.
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1.1 Red Bloods (Cartman and Bebe)
0.1 Boa Constrictor (Victoria)
0.1 Albino Burm (Butters)
0.0.1 Desert King (Miles)