Reptile & Amphibian Forums

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I can't explain it with a bunch of genetic lingo but the hypo trait is a co-dominant/dominant trait. If you breed a hypo to a normal, you end up with half the litter being co dominant hypo. If you breed 2 co-dominant hypos together, you end up with mostly dominant hypos because the trait has been "strengthened", pretty much. That's the way the trait works. Hard to explain I guess, but easy to understand.

No disrespect meant towards Ryan's reply,but,the "Salmon/hypo/Orangetail" trait has proven,over multiple generations to be "simple dominant" in its hereditary nature. Of all the genetic mutations we currently work with,it is the easiest & most straightforward to understand...even though breeding a het. albino produces the SAME 50/50 split when bred to a "normal",we don't call these hets "co-dominant". we know that the trait itself is "recessive",and,we correctly say so...I'm not sure why so many people have such a hard time accepting "hypos" as "dominant"...but,that's what it is,plain & simple...no need for confusion,don't need to be a scientist,or,geneticist to comprehend it...but,you DO have to clear your head of all the misinformation floating around. most of us are just hobbyists,but,this stuff isn't rocket science,it's just simple application of common sense,available evidence & very basic genetic theory,combine the three & have some fun!

Thank you, I would have said the same. Our discussion a while back did help a wide range of people to learn about the difference in genetic inheritance modes, but there is still all the old bad information to be corrected and removed.

A "dominant" hypo is the homozygous,(or,"super" ) form of the hypo trait...in order to produce one,BOTH parents need to be "hypo" gene carriers...the same is true of albinos,for example---You cannot produce an albino unless BOTH parents being bred carry the trait,either as a het.,or,homozygous albino.the big difference is that we can SEE which babies are het. for the hypo trait,whereas the albino mutation is recessive in the first generation.(when bred out to a non-gene carrier.)

I would like to ask what would be considered "co-dominant"?
I was going to throw a hypothosis up here but I have a feeling it would be wrong and I won't make myself look any dumber than I already am lol

thanks for the education, I love these discussions I always pick up something new.

This was posted in the ball python forum by Paul Hollander last week. While it uses pastel ball pythons as an example, I still think it can help a lot of people out. Paul, I hope you don't mind me posting this.

Also, April, hypos are dominant because you can't distinguish a "super" hypo from a "non-super hypo". This is because when you pair a hypo allele with a normal allele, the hypo allele is dominant to the normal one and fully expresses itself. An example of a codominant gene is the motley. When the motley gene is paired with a normal allele, it partially expresses itself and the normal allele partially expresses itself. They are codominant, rather than one being dominant to the other. Now, when you pair two motley alleles together, you get the purple patternless (I know not proven yet, but come on). In this case the motley allele is able to fully express itself without the normal allele trying to bully its way in. Hope this helps April.

Now for Paul's post regarding pastel ball pythons:

""Super" has absolutely no standing in standard genetics terminology. In herper slang, a super is an animal that is, in standard genetics terms, homozygous for (has a pair of) either a dominant or a codominant mutant gene. This useage got started from the super tiger reticulated python and has been extended to animals that are homozygous for a dominant mutant gene like salmon in boa constrictors.

Animals are NOT dominant or codominant. Animals are (homozygous or heterozygous) for a (dominant or codominant or recessive) mutant gene. A mutant gene is dominant or codominant or recessive to its normal allele.

"Partial dominant" is a full synonym for "incomplete dominant". For practical purposes, "incomplete dominant" and "codominant" are synonyms. "Partial dominant", "incomplete dominant", and "codominant" are NOT synonyms for "heterozygous" except in herper slang, which has no standing in standard genetics terminology.

If a ball python has two copies of the pastel mutant gene, it is homozygous pastel. If a snake has a pastel mutant gene paired with a normal gene, it is heterozygous pastel. And pastel is a codominant mutant gene because a homozygous pastel can be distinguished from a heterozygous pastel just by looking at them.

In other words, a ball python with two copies of the pastel mutant gene is not a "dominant pastel". It is a homozygous pastel ball python. A snake with a pastel mutant gene paired with a normal gene is not a "codominant pastel". It is heterozygous pastel. And pastel is always codominant to its normal allele. It does not matter whether a snake has two copies of the pastel mutant or a pastel mutant gene paired with a normal gene; pastel is a codominant mutant, period.

Clear as mud?

Paul Hollander"

Hope this all clears some things up. Rainshadow, if I screwed any of this up, please correct me.

Thanks,
Matt Crabe

this part:
"An example of a codominant gene is the motley. When the motley gene is paired with a normal allele, it partially expresses itself and the normal allele partially expresses itself."

explained it to me very clearly, I was thinking the co-dominant
had something to do with two expressions having an effect on each other so I was headed in the right direction.
Thanks!

Your thinking of the two genes haveing effects on one another is incomplete dominance (yes for practical purposes they are synonyms but there is a difference).

Look at flowers, red a white flowers when bred together create pink, because the two genes are incompletely dominant and duelly express themselves. Confused?

Chris,
You're right that incomplete dominant and co-dominant are not exactly the same. I chose to leave that part out of this discussion in order to not confuse the matter. I should have stated that there is a difference but chose to leave it for another discussion.

Matt

From what I've found, the difference between "incomplete dominance" and "codominance" (both used in the strict sense) has to do with functionality of the gene products. In incomplete dominance, one gene has a nonfunctional gene product and the other gene has a functional gene product. In codominance, both genes have functional gene products.

With many mutant genes, we have no idea of the functionality of the gene products. In both cases, on the whole animal level, the heterozygote can be distinguished from both homozygotes. On that level, the two terms are synonyms. As "codominance" is the shorter term, I generally use it in preference to "incomplete dominance".

Paul Hollander

I'm sure Paul won't mind I'm glad he's spreading himself around! *lol*

I would have copied that post, too, if I'd gotten into the discussion earlier.

Paul Hollander

I think it saved me another big headache. I'm still getting over the one from last week. I hope you didn't mind.

Matt

The only time I mind people recycling my posts is when they get taken out of context or I could do a significantly better job in a newer version. Neither applies in this case.

Paul Hollander

As of right now a lot of work is still needed with Boa morphs. However it can be said the Motley and Jungle mutations are co-dominant. The difference in co-dominant and dominant mutations is that in co-dominant mutations the Heterozygous and Homozygous animals look different from one another, where in dominant mutations that Hets look like the Supers. Does that make sense?

I think I get it now.
but of course I'm sure something weird will pop up next year to throw us all for a loop again.

thanks for the help!

is the mutation only expressed in HALF (approx) the litter when a hypo is bred to a normal? I always thought that a DOMINANT gene would, be just that ..... dominant over the genetics of a normal animal thus expressing itself???

OK - so as per above, then are their different levels of dominance in genes? Correct me if Im wrong but if a hypo boa is a simple dominant trait, in which the het and homo. forms look alike, then why does only half of the litter express the "dominant" gene. I understand the word "dominant" to mean that it will express itself over the genetics of a normal animal.

I certainly understand the explination of co-dominance. It makes sense since the het and homo. forms look different.

Care to clarify?

Breeding a Homozygous Hypomelanistic Boa to a non Hypo yields 100% Hypos in the heterozygous form. That is the offspring have one allele. Those with one allele are het for the trait and when bred to a non hypo half are The heterozygous form of hypomelanism.

Think of it this way, if you breed a het albino to a normal half the babies are hets and half not, thus 50% poss hets. In the Hypo's case we simply know which are hets and which are not.

Also just for clearification. Hypomelanism is not recessive, Heterozygous animals are any animal that carries only one allele for a given trait as opposed to a matching pair, the Non-Supers.

n

If you breed any hypo to anything other than another hypo,and,get 50% expression....your "hypo" is a het!!!(as opposed to a "super"...in its homozygous state it IS dominant over the non-expressive counterpart...make sense?(why do you get 50/50 when you breed a het albino to a "normal"? because your albino gene carrier is a "heterozygous" form of the mutation!)this isn't "co-dominance" this is standard transmissive inheritence as expressed by a heterozygous example of any genetic mutation...it's very basic Mendellian genetic theory.

/

I think a lot of people get confused because super hypos are often referred to as dominant because they carry a pair of mutant alleles. The words dominant, codomninant, and recessive really refer to how the mutant allele interacts with a normal allele. In a dominant trait, the mutant allele dominates the normal allele and expresses itself solely. In a codominant trait, neither the mutant allele nor the normal allele completely express themselves; they kind of blend together. In a recessive trait, the normal allele dominates the mutant allele and expresses itself fully. You can think of recessive and dominant as inverses of each other. The only difference is that the standard is to state how the mutant allele acts in relation to the normal allele, not the other way around.

Matt

This 50% split we always talk about is based strictly on probable,statistical odds as they relate to calculations we make using Punnett's square,in an attempt to predict the potential outcome of various genetic combinations...in order to use what we know about genetics,we must identify & assign a behavioral characteristic to a given mutation...that being said,it is entirely possible to breed a het.hypo & get less,(or,more)than 50% expression in the resulting litter. This year I bred a het.hypo to a non-hypo,out of 10 babies,only three were hypo...so 50% expression is not guaranteed,merely implied by statistical averages.(imagine if this breeding had involved a het albino bred to a "normal"...the litter would be sold as 50% poss. het.,when in fact only 3 babies would've actually been heterozygous!)

Absolutely right. I bred het albino to het albino this year and got 5 albinos out of 28. Based on the punnett square, there should have been 7 out of 28.

Matt

developing neonate. In otherwords, it isnt necessarily the case that 50% of the litter will be hypos as a whole (in the above example of hypo to normal) but rather that EACH of the 10 babies have a 50% chance of being hypo in and of themselves.

flip a coin for 3 sets of ten. The first set you may get heads 7 out of 10, the second maybe 4 out of ten and the third ..... who knows.

Correct??

>In a codominant trait, neither the mutant allele nor the normal allele completely express themselves; they kind of blend together.

This is the only part of the preceeding post that needs to be clarified a little, in my opinion.

Both the codominant mutant gene and the normal gene completely express themselves in the cell, on the molecular level. Neither the genes nor their molecular products blend together. It is the effect of both molecular products, with each one doing its own thing in the cell's biochemical machinery, that produces the blending effect that appears in the whole animal. An analogy might be a soprano singing the tune and a baritone singing harmony in a duet. As opposed to two sopranos singing the tune part or two baritones singing the harmony part.

Paul Hollander

"Both the codominant mutant gene and the normal gene completely express themselves in the cell, on the molecular level"

So in both co-dominant and incomplete-dominant both traits are
expressed but in the co-dominant form the more dominant alle
(motley in the case of motley boas) overrides the other 'normal'
alle and in incomplete-dominant the two alle/traits are blended together. Do I have it yet?
Are there any incomplete-dominant traits out there?

TGIF

>So in both co-dominant and incomplete-dominant both traits are
expressed but in the co-dominant form the more dominant alle
(motley in the case of motley boas) overrides the other 'normal'
alle and in incomplete-dominant the two alle/traits are blended together. Do I have it yet?

You don't have it quite yet.

First of all, traits are what you see. For example, motley is the name of a trait (a pattern) and the name of a mutant gene. Genes are in the cell. Genes produce various chemicals that interact with the biochemical machinery in each cell and ultimately produce the traits that we see. Genes are passed to the sperm and the egg, but melanin is not passed to the sperm and egg. So the gene that produces the motley pattern is inherited, but the actual motley pattern of markings (the trait) is not inherited.

A DOMINANT allele masks the presence of a RECESSIVE allele. In a boa with an albino mutant allele paired with a normal allele, the normal allele masks the presence of the albino mutant gene. The boa looks normal. That makes the normal allele dominant to the albino allele and the albino allele recessive to the normal allele. In a boa with a salmon mutant allele paired with a normal allele, the salmon mutant allele masks the presence of the normal allele. The boa looks salmon. That makes the salmon allele dominant to the normal allele and the normal allele recessive to the salmon allele.

With dominant and recessive alleles, there are TWO traits. There is one trait for the animal that is homozygous for the recessive allele (a pair of identical recessive alleles). And there is one trait shared by the animal that is homozygous for the dominant allele (a pair of identical dominant alleles) and the heterozygous animal (with a dominant allele paired with a recessive allele).

With both CODOMINANT and INCOMPLETE DOMINANT alleles, there are THREE traits. One trait for one homozygous animal (with a pair of identical copies of one allele). One trait for the other homozygous animal (with a pair of identical copies of the other allele). And the third trait for the heterozygous animal (with a pair of genes made up of one copy of each of the two alleles). Lumping the two categories together is actually good enough for breeders' and sellers' purposes. I follow my old genetics prof in calling that lumped together category "codominant" because it is shorter than "incomplete dominant" and much shorter than "codominant/incomplete dominant".

By convention, we call the normal allele the standard of comparison with the mutant allele assigned the dominant or recessive or codominant position. If there are three or more alleles, each pair of alleles is compared.

If you really want to get into the morass of verbiage required to explain the difference between "codominance" and "incomplete dominance", then continue. You might prefer to stop here, though.

Biochemistry and molecular genetics mostly take place inside a single cell. And all that gets really complicated really fast. Molecular genetics and the phenogenetics involved in breeding boa morphs are two different levels of organization.

On the molecular genetics level, genes do their own thing. The albino mutant gene does its own thing and the albino mutant's normal allele does its own thing whether there are two albino mutant genes, two normal alleles, or an albino mutant gene paired with a normal allele. The same is true for all genes, whether mutant or normal or whether dominant, recessive, codominant or incomplete dominant. In other words, if there are two different genes in a gene pair, each one produces its own product inside the cell. The two products do not form an intermediate or blended product. It is the mixture of those two products in each cell that gives rise to what we see in the whole animal.

Lets say that we have an individual snake that has a codominant mutant gene paired with a normal allele. If we could look inside each cell, we would see a mixture of two different gene products. One product would be made by the mutant gene, and the other product would be made by the normal allele. If we looked at the whole animal, we would probably see a blended or intermediate effect in comparison to a snake that has two mutant genes and a snake that has two normal alleles.

Lets say that we have an individual snake that has an incomplete dominant mutant gene paired with a normal allele. If we could look inside each cell, we would see a mixture of two different gene products. One product would be made by the mutant gene, and the other product would be made by the normal allele. If we looked at the whole animal, we would probably see a blended or intermediate effect in comparison to a snake that has two mutant genes and a snake that has two normal alleles.

If you read the last two paragraphs closely, you will notice that the only difference is that one says "a codominant mutant gene" and the other says "an incomplete dominant mutant gene".

By now you are probably wondering whether there really is any difference.

Here is the difference:

In codominance, both alleles make products that do something in the biochemistry. It is the mixture of two functional products that causes the differences between the heterozygote and the two homozygotes.

In incomplete dominance, only one of the two alleles makes a product that does something in the biochemistry. The other allele makes a product that does nothing in the biochemistry. And it is the different amount of functional product in the heterozygote that causes the differences between the heterozygote and the two homozygotes.

>Are there any incomplete-dominant traits out there?

There are no incomplete dominant traits, no codominant traits, no recessive traits, and no dominant traits. There are dominant, codominant, incomplete dominant, and recessive mutant GENES. The genes cause the traits that we see. That is a difference between "trait" and "gene".

Some mutant genes are incomplete dominants, and some mutant genes are codominants. That is, in the strict sense of the functionality of the gene products as given above. But I cannot give any examples in the boa constrictor. Because I do not know whether or not a given mutant gene's product is functional. We can tell whether a heterozygote can be routinely distinguished from the two homozygotes, but that simply returns to lumping incomplete dominants and codominants into one category rather than separating them.

Hope this helps.

Paul Hollander

Wow!!!! After reading that and actually understanding it on a Friday afternoon, I think I deserve a beer now. Great post Paul.

Matt

d

Paul,that may be the single most valuable post I have ever read! I've saved it as a document,because I'm sure I'll have to read it several times to soak up the full content.For someone like me,who has a basic understanding of these principals,but,lacks the eloquence,and,more importantly the EDUCATION to fully,or,accurately EXPLAIN the concepts...it's like finding a perfectly cut diamond in a truckload of sand...thank you,& I'm glad you take the time to contribute on these Forums!

Great to see that what I thought was just a simple question turned out to be so interesting and informative!!! Thanks again.

So, if I'm looking to buy a hypo, then it doesn't matter if it's called a dominant or not, as long as it's a visible hypo.? Also there is no such thing as being "het for hypo" right?

Don't say it doesn't matter. Are you planning to breed, or do you just want a Hypo? If you have a homozygous all of its offspring will be hypo, if you have a heterozygous hypo only half will be.

Also, It is important to remember that if a Boa carries a gene for Hypomelanism it will be Hypomelanistic. No normal appearing hets.

Sorry, I'm still trying to grasp all of this. Yes, I'm looking for hypos to breed. I thought, for example, that a hypo bred to say, a normal, would produce about 50/50. But a "dominant hypo" when bred to a normal is going to produce 100% hypos?? I'm still confused about the het hypo. I thought a boa could not be normal looking and be het for hypo. And you're saying that buying dominant hypos would be a better choice, right? Sorry again if I'm butchering this whole thing. Thanks

The mutation that causes Hypomelanism is inherited through dominance, the mutation is dominant not the animal.

I will try to put this accurately, but simple. A non-super hypo when bred to a normal will give a 50/50 ratio, odds derived by punnet squares. A Super Hypo when bred to a normal will give 100% hypo offspring, however each of those is a non-super.

Here is the heterozygous part. An animal that has just one allele for a trait is heterozygous, if it has a matching pair of alleles it is homozygous. A Super is homozygous, and should be called a homozygous hypo not super. A non-super is heterozygous and should be called a heterozygous hypo. The difference here between say albino offspring, the het hypos look like the homozygous hypos.