Questions regarding genetics . . .

[TBurkeIII]

i know that sometimes when two worlds collide it can sometimes cause a mess. that happens alot with boas and ball pythons. i am not really trying to bring those two worlds together cause they don't really belong together. but, unfortunately my understanding of some things is based from my knowledge with other things. i understand what serp is saying, but with my understanding of co-dom is that statistically half of the offspring usually is 50% of that trait that is co-dom. (for example) if bloodred were to be co-dom...shouldn't a percentage of the offspring produced when bread to a normal be bloodred? not het for blood?
and i don't really take offense to the boa worlds understanding of genetics. it is not to say they don't understand it, but it does tend to be explained in simpliest terms sometimes eluding the proper genetic definitions to make understanding simpler. i dont agree with this method at all but that is how it is. in my mind they tend to make short-cuts for themselves because there are not as many morphs or genetic combonations to the snakes, this results in some confusion now and definately confusion down the road. thanks guys

 

[Hurley]

(for example) if bloodred were to be co-dom...shouldn't a percentage of the offspring produced when bread to a normal be bloodred? not het for blood?

I'm not trying to harp here and I'm not trying to put the boa world down, just trying to inject some reality here. Quite honestly I'm hoping to explain why it is important to learn the different definitions and to understand why the way "co-dom" is used in the boa world is confusing, inaccurate, and is doing more harm than good while they are trying to teach people boa genetics and teach new people what to expect from crosses. Unfortunately the term has been fudged for so long that everyone just accepts the range of definitions as fact and they never bother to question the base knowledge (definitions of their terms) or look at what they are truely saying.

The problem here is that in the boa world, somehow codominant has come to mean phenotypes, geneotypes, and morphs of snakes. The word has nothing to do with any of these things. It kind of reminds me of the South Park word Marklar. Marklar can mean any word and is just inserted to mean many different things, some of which are mutually exclusive of each other. It gets very confusing. The word codominant is very simple and relates to the relationship of one allele (version of a specific gene) to another (different version of a specific gene).

Codominant is not a phenotype (i.e. this salmon boa when bred to a normal throws half codominants, just like dad).

Codominant is not a genotype (The results of that breeding are normals, super salmons, and codominants).

Codominant is a definition of how two genes relate to each other at the same locus (meaning they occupy the same space on the DNA chain). If at the "white" locus a "red" gene exists and is codominant, then WW will be "whites", RR will be "reds", and WR will be something different from white and red, and could be anything from nearly white to nearly red, falling in the "pink" category somewhere.

Codominance simply means that those genes' relationship to each other are not all or nothing. That's it. They both have some amount of effect (that amount of effect from each gene can be quite variable). When you have a codominant gene pair, your have 3 possible phenotypes (morph outcomes). Diffusion (bloodred) seems to fit into this category. There are 3 phenotypes. Normal (no diffusion gene), Bloodreds (both diffusion genes), and the heterozygous version which may look anything from darn near normal to darn near bloodred (het for diffusion) and is quite variable. What you DON'T get breeding a bloodred to a normal (non-het) is Bloodreds. This defines that the gene is NOT dominant. You also don't get a whole clutch of perfectly normal animals. The gene is NOT recessive. You get a whole clutch of animals with varying degrees (from slight to a lot) of diffusion of the pattern. These are the result of the het status of this codominant gene pair.

Dominant traits only have 2 phenotypes. They either are or aren't "blue" or "patternless" or whatever. Doesn't matter if the animal is het for the trait, or homozygous, they look the same. That is a dominant gene pair. Dominant traits are the ones that when bred to a totally normal animal will produce the morph in the first generation. Dominant traits also, though, show no difference when an animal carries 2 mutated genes or one. They look identical. One gene is enough to make the effect happen entirely. The best example of dominance that we are all familiar with is the "normal" gene when paired with any recessive trait. Normal is dominant to amel, it doesn't matter if the animal is het for amel or totally normal (not het amel)...the animal looks normal. The normal gene at the amel locus is dominant.

The problem I've had in trying to converse with people in the boa world is that they don't seem to understand dominance vs. codominance. They will breed a new trait once and get some "blues" and some normals in the clutch and call the trait codominant. This is a premature assumption. What you do know from that pairing is that the trait isn't recessive...but that's it. Until you get a homozygous form and prove that out, you don't know the relationship of the gene Codominant vs. Dominant.

Ex: You breed this new blue to a normal and get half blues and half normals. You breed the blues together and get 3/4 blues and 1/4 normals. Chances are that gene is a Dominant gene (unless you were unlucky and no homozygous animals popped out). You breed all blues back to normals and some throw half blues, half normals. Some throw all blues that look just like the parents = the trait is Dominant to normal.

Or you breed the new blue to a normal and get half blues and half normals (just like the previous example). You breed the blues together and get 1/2 blues, 1/4 normals, and 1/4 greens. You've got a codominant trait. Breed the green to a normal to test...you get all blues (het form). Breed a green to a blue and get half blues, half greens. Then this trait is Codominant to normal.

Can you see why this quote makes no sense? Even if I fudge a little and use codominant as a genotype?

(for example) if bloodred were to be co-dom...shouldn't a percentage of the offspring produced when bread to a normal be bloodred? not het for blood?

If "bloodred" is codominant... ("bloodred" being the full diffused pattern trait) ...shouldn't some of the offspring be "bloodreds" when bred to a normal? NO. If "bloodred" is codominant, then when bred to a normal, all of the offspring should be something between "bloodred" and normal. "Bloodred" being the homozygous form.

...not het for blood? They should be het for blood because "bloodred" is the homozygous form. It has both "bloodred" genes.

The problem, I am guessing here, is seems you are using the boa logic of "X" gene and super "X", where the gene is named after the heterozygous version's phenotype. (Like Salmon, Tiger, etc.) These genes got named for the het version of a codominant gene, so when the homozygous version rolled around, those got called "Super Tigers", etc. Unfortunately the name of the gene got associated with the het version of a codominant gene pair before the homozygous version was ever created. That's the danger of getting a new codominant gene and naming it before you ever prove it out as dominant or codominant.

If that isn't the case, then I honestly can't follow your logic. :shrugs: I really feel bad for people getting into boas with all the hazy pseudogenetics thrown about. I know of one friend in particular that got ridiculed by the "higher ups" in the boa world for daring to read about genetics and then apply it to what they were seeing with the traits. He obviously did not know what he was talking about, right? He's new, what could he know? Yet, they couldn't answer his questions or defend their position, so they blustered and buffalo'd. It's sad, really. It would help if some of them could pick up a simple genetics primer and sit down for a bit, drop their preconceived notions and read with an open mind. I feel if they did that, a light may come on and it would elminate a lot of confusion. I know I'm a dreamer here and it won't happen, but it would be nice. People don't like to question the core of what they understand their knowledge base to be.

 

[Serpwidgets]

At the diffused locus as it is currently described, there are three possible genotypes:
1- D⁺·D⁺ is the normal phenotype.
2- D⁺·D^D
3- D^D·D^D is expressing the diffused pattern.

#2 is neither normal or diffused. Sometimes it can look pretty much normal, and sometimes it can look almost completely (but not quite) like a diffused corn. By definition, these two alleles are codominant to each other.

(At any autosomal locus with one wild type allele and one mutant allele, there are always exactly three possible genotypes. Any one-locus cross [no matter how many mutants are involved] is always exactly the same math, which can be determined by FOIL.)

Going back to the "if you cross x to y" stuff...

If you cross D⁺·D⁺ X D^D·D^D then all of your offspring (as shown by FOIL) will be D⁺·D^D. That is, if you cross a normal to a bloodred, NONE of your offspring will be bloodred. But they will all be het, and many will tend to show some expression of the diffused pattern as a result of carrying that single copy of the pattern mutant.

Again, the key question is "Does #2 look just like #1 or just like #3?"
If yes, then one is dominant and the other is recessive.
If no, then the two alleles are codominant.

 

[Serpwidgets]

To answer these specifically (as best I can try to translate, hehe)

i know breeding boas that when you take an arabesque(pattern) gene which is co-dom in boas, and breed it to a normal you will have a percentage of the litter to be arabescque.

This is assuming the following:
A⁺·A⁺ = Normal
A^A·A⁺ = Arabesque
A^A·A^A = ??? (Do these look exactly the same as any arabesque?)

If you cross A⁺·A⁺ (Normal) to A^A·A⁺ (Arabesque) then FOIL shows you that the offspring will be
A⁺·A⁺ (Normal) and
A^A·A⁺ (Arabesque)

This is true if Arabesque is fully dominant, and it is also true if Arabesque is codominant.

The results from A⁺·A^A (Arabesque) X A⁺·A^A (Arabesque) will be:
A⁺·A⁺ (Normal)
A⁺·A^A (Arabesque)
A^A·A^A (???)

The genotypes from this cross will always be the same. The question is what are the phenotypes?

If ??? looks like any other Arabesque, then Arabeqsue is dominant.

If you get what people will want to call "super arabesque" then Arabesque is codominant to its normal allele. In this case, the "super arabesque" are simply homozygous for the arabesque allele. (They are not "double dominant" and they are not "the dominant form of a codominant gene" which are other terms I've heard used.)

In other words, when you say "Arabesque" do you mean the heterozygous genotype?

now if you take a blood boa and breed it to a normal boa you will get all normals het for blood...but some of those babies will have some traits that can resemble a blood boa. that does not make it a co-dom trait. it is still recessive.

This is where boa genetics goes completely off track and is 100% wrong. (It's also why it gets so confusing and complicated.) The above shows that the blood allele is codominant (most definitely not recessive) because the heterozygote shows an intermediate phenotype.

The translation is:
"If you cross B^B·B^B to B⁺·B⁺ all the offspring are B⁺·B^B and will have some traits that can resemble a blood boa."

Add to the above, "if you cross (some traits that can resemble a blood boa) which is the B⁺·B^B genotype, to a B⁺·B⁺ (normal) then you will get:
B⁺·B⁺ (Normals) and
B⁺·B^B (some traits that can resemble a blood boa)"

Does that help at all?

 

[TBurkeIII]

serp and hurley i appreciate your descriptions on this matter. i understand now what the proper descriptions would be. i think that you make perfect sense and i understand fully. in defense of SOME of the boa world i will say that alot of times things get simplified as i stated earlier. i am not saying it is right or wrong. that is the way it is understood by some people. i do however believe that there ARE people in the boa world who are extremely willing to pick up books and do research. the people i know see that aspect of it as being the most interesting part. it is not about just popping out babies and making a quick buck, as i am sure many people think. breeding snakes has been one of the most positive aspect of my life which is why i continue to progress with it as much as i can. i also know that if we were to have these same conversations with some big shots in the ball python world or whatever, it would again be a different discussion. some people handle things their own way and i myself would not like that to make me a one track person who only deals with corn, or boas or whatever if i don't necessarily agree with their ways of handling things.

 

[TBurkeIII]

ok... this from breeding trials i have seen are that if you throw an arabesque into the mix of a normal, 50% of the offspring will be arabesque...there is no mistaking the difference between and arab and a normal, they either are or they arent arabesque. if this were to be dominant then wouldn't all the offspring be arab?

with the blood gene in the same instance there are possibilities of having some offspring with slight (if any at all) indications of the blood boa. thos suckers would just be het for blood?

if this is all true that blood boas are co-dom as you are saying than why is the "normal" gene dominant completly over the blood with MAYBE some slight indication of color variance?

 

[Serpwidgets]

ok... this from breeding trials i have seen are that if you throw an arabesque into the mix of a normal, 50% of the offspring will be arabesque...there is no mistaking the difference between and arab and a normal, they either are or they arent arabesque. if this were to be dominant then wouldn't all the offspring be arab?

This only says what two of the genotypes are. You need to know the phenotypes associated with all three genotypes in order to answer this question.

If I say "5 - n is NOT a negative number" then you only know that n is not greater than 5.

What you do not know is whether n=5, or n<5. Either could be true. Right?

So, what we do know is this:
If you breed an arabesque to a normal and get some arabesques and some normals, then that particular arabesque boa is heterozygous. (A⁺·A^A)

One way to determine whether it is codominant or fully dominant is to cross two of these hets together. This will produce a clutch where 25% of the offspring are expected to be homozygous arabesque (A^A·A^A)

If these homozygous individuals look exactly like other arabesque boas, then the A^A allele is dominant. Otherwise, you'll get a third phenotype and this will show that it is codominant, with the heterozygotes being the ones that you identify as arabesque.

The other way is if you have some arabesques which, when crossed to normals, produce clutches where they are ALL arabesque and NO normals. If this happens, you can say that these arabesque boas are homozygous A^A·A^A and that their offspring are all heterozygous. Since the hets will look the same as the homos, you can then say that A^A is fully dominant to A⁺ and not codominant.

 

[paulh]

ok... this from breeding trials i have seen are that if you throw an arabesque into the mix of a normal, 50% of the offspring will be arabesque...there is no mistaking the difference between and arab and a normal, they either are or they arent arabesque. if this were to be dominant then wouldn't all the offspring be arab?

Sorry, no. This just shows that the arabesque in this mating is heterozygous arabesque. IOW, it has an arabesque mutant gene paired with a normal gene.

Unfortunately you are following the boa definitions of "dominant" and "codominant".

The boa definition of "dominant" is the standard genetics definition of "homozygous for a dominant or codominant mutant gene". And the boa definition of "codominant" is the standard genetics definition of "heterozygous for a dominant or codominant mutant gene".

Here is a table that may help clarify the standard genetics definitions. Hope it helps. (There is a big gap here before the table appears; I don't know why.)

<table>
<tr>
<td> </td>
<td><b>homozygous for a mutant gene</b></td>
<td><b>heterozygous (a mutant gene paired with its normal allele) </b></td>
<td> <b>homozygous for the normal allele</b> </td>
</tr>

<tr>
<td><b>Mutant gene is dominant to normal allele</b></td>
<td> full mutant phenotype</td>
<td> full mutant phenotype</td>
<td>normal phenotype</td>
</tr>

<tr>
<td> <b>Mutant gene is codominant to normal allele </b></td>
<td>full mutant phenotype</td>
<td>phenotype not normal but not identical to full mutant phenotype</td>
<td>normal phenotype</td>
</tr>

<tr>
<td> <b>Mutant gene is recessive to normal allele</b> </td>
<td> full mutant phenotype</td>
<td> normal phenotype </td>
<td> normal phenotype </td>
</tr>
</table>

 

[Serpwidgets]

if this is all true that blood boas are co-dom as you are saying than why is the "normal" gene dominant completly over the blood with MAYBE some slight indication of color variance?

Just to make sure we're saying the same thing... I'm not saying "blood boas are codominant" I'm saying "the blood TRAIT is codominant." (Not trying to play semantics, but there's a big difference between those two statements.)

I'm saying that:

1- the blood allele (B^B) is codominant to its normal counterpart (B⁺) ("the blood TRAIT is codominant")

2- blood boas are homozygous for the blood allele. (B^B·B^B)

The statement "with MAYBE some slight indication of color variance" is the "third phenotype" which makes it a codominant. Sounds like the amount of expression varies.

When you get down to "sometimes you can't tell" then it's more a matter of "which term is a more useful description" rather than "which term is technically correct." This is why I prefer the term "variable codominant" for the diffused gene in corns, and I'd say this is probably a good description for the blood gene in boas... in the end what is important is whether or not we are able to use that description to predict the outcomes and/or identify the hatchlings.

So you can say "it's usually recessive" or "mostly recessive" or "pretty much recessive but not always" or "kinda codominant" or many similar things and it would be "close enough for government work."

 

[paulh]

1- the blood allele (B^B) is codominant to its normal counterpart (B⁺) ("the blood TRAIT is codominant")

1- the blood allele (B^B) is codominant to its normal counterpart (B⁺) ("the blood MUTANT GENE is codominant").

A trait is a difference from the normal phenotype. That difference is caused by one or more mutant genes.

 

[Serpwidgets]

A trait is a difference from the normal phenotype. That difference is caused by one or more mutant genes.

LOL, that too.

 

[TBurkeIII]

i got ya on that one...that made it a bit better to understand we are on the same page. that clears up where there was some confusion on my other previous post. the "most useful description" term as opposed to "technically correct" term. thanks

 

[Serpwidgets]

"the blood TRAIT is codominant"

I'm reconsidering whether or not it makes sense to say "a trait cannot be recessive." I've been going back and forth on the usage of "recessive phenotype" versus "recessive allele" since I ran into this information about the sickle cell gene. The thing is, it causes several phenotypes: anemia, sickle-cells, and resistance to malaria.

The anemia is present only in the "homozygous for mutant" genotype. (It is recessive to normal.)

The sickle-cell is present in heterozygotes but more extreme in the "homozygous for mutant" genotype. (It is codominant to normal.)

The resistance to malaria is present in both heterozygotes and in the "homozygous for mutant" genotype. (It is dominant to normal.)

So the problem is, if you only use dominant/codominant/recessive in terms of two alleles, the above cannot be described "correctly" on any one count without being wrong on two counts. :crazy02: The only way to make sense of it is to say each trait individually is _______ to normal.

Obviously, this is just geeking out on the semantics of it all, because for all practical purposes, it still functions the same way when it comes to the traits we're working with (for now...) Whichever way you try to describe the traits we're working with and the alleles that cause them, as long as we all can communicate to each other what it is, and as long as we can all understand how they are inherited and expressed, and predict outcomes and identify what we've hatched, that's what counts.

 

[TBurkeIII]

i understand what you are saying...it terms of corns i believe things need to be quite specific when dealing with situations of this nature because there are so many possibilities genetically. the problem i have for other areas i.e. boas or pythons, is that situations are sometimes simplified by people because the snakes are not as advanced genetically as corns are( although Ball Pythons are beginning to catch up quick )LOL. this will eventually, in my mind, catch up with the hobby and breeders of those areas in the future. there will be confusion on some level to figure out "what is going on where." i feel that if all breeders keep proper records of what is going on with their snakes they will prevent future generations down the line from having mysteries within their offspring. obviously it is impossible to control this completely but that's just my opinion. by breeders and buyers not being fully aware of what they have or breeders not telling buyers what they have just causes caos, and that just makes situations very confusing.

 

[ecreipeoj]

Tom,
I feel for you. You are in the middle of the Corn Snake World and Boa World. Basic genetics is basic genetics. It is very simple. The Boa World has made up their own language that has nothing to do with, or very little to do with, basic genetics. They understand their language, but it is not correct.

It reminds me of Mike Shivers understanding of the Ultra gene. He had it completely figured out in his mind, even though he was totally wrong about what he believed was happening when he bred the Ultra, Ultramels and amels, but to him it made perfect since. The problem with this approach is that you have to totally ignore some of the results that don’t fit into your understanding of your genetic language. If you do this it works fine, but it is not correct.

Just wait until the Boa World discovers two mutant genes that are alleles. They can not grasp a co-dominant mutant to normal, how will they grasp two mutants that are alleles and co-dominant to each other. They will have to come back to basic genetics then, but it will be like watching World War III. It is bound to happen very soon. I can’t wait!

I respect a lot of people in the Boa World, but there is a serious power struggle over their with some very big egos. Their husbandry and breeding techniques are unquestionably very professional, but the way they apply basic genetics to the mutants they have bred is not completely accurate. I tried to get involved and pointed out some areas that could be corrected and it was not received well to say the least.

It seems extremely likely that the Salmon mutant gene (Hypo) and the Arabesque mutant genes are dominant to normal. A Super Salmon (Homo Hypo) and a Salmon (Het hypo) look identical. The same is true with the Arabesque. The breeders that have been breeding them the longest and have produced the most can not tell them apart. The Salmon Boas have been selectively bred to be cleaner and lighter, but dark ugly Salmons or dark Ghost Boas can be Supers (homo Hypo) and produce 100% Salmons or Ghost Boas when bred to Normal or Anery in the Ghost case. This hypo gene is dominant to normal. They seem to use the co-dominant term for a boa that is het for a dominant gene.

Some Boas mutant genes seem like they are going to be co-dominant to normal. They have been named for their het mutant look, exactly like Serp said. A Jungle Boa is Het for the Jungle mutant. A Super Jungle is homo for the Jungle mutant and is more radically aberrant. It is actually very simple. The het Jungles can almost look normal and/or be very aberrant looking. This is a very classic type co-dominant gene. It reminds me of our Aztecs.

The Blood Boas sound like our Caramels Corns, which I believe may be co-dominant to normal now that I have been sucked into basic genetics by Serp and others. Many of the old Corn Snake breeders, were much like the Boa Breeders. They thought they had it figured out, but perhaps they did not.

Another possible co-dominant gene is the Motley Boas. They may be named for the Het Motley phenotype as well. The Super Motleys (Purple Boas, AKA Purple Patternless ) may be the Homo Motley phenotype. It has not been proven yet. There are other possibilities, but don’t tell them that or you will be strung up. The Purple Boas could be cause by a recessive gene contained in the Motley line, or if my wishes come true, it is an allele to Motley. I suggested these two very real possibilities on a Boa Forum and was crucified. Very tactfully by some, and put in front of a firing squad by others.

This Boa Genetic Language is why you and many others got in a big debate about the T+Albinos. They are simply a nice extreme recessive hypo mutation, like a Sunkissed, or Lava hypo Corn Snake. The Boa world will not accept this because of the dominant hypo gene that is called Salmon or Orange Tail, but the T+ Albino Boas are a recessive hypo gene and nothing more. They are totally cool by the way.

 

[TBurkeIII]

yeah joe ...i do know what you are saying. i have spoken to people in the boa world about the way things get passed on, and why things would be so different in the corn world as to the boa world. but, really they are not when it comes to genetics by the true term. i have said just what you have pointed out, that one day it will just be mayhem and everyone will be scrambling to try and figure out what the hell happened and when? when i was 4 years old i got my first pair of Brazilian Rainbows in my house and we never looked back form there. that was 20 years ago. now just recently (2 years ago) i noticed my untapped interest in corn snakes. it is like completely retraining your brain for something totally new. there is a big part of me that really likes that aspect. if i were to get my hands on some boas that i can really call my own, i would really have no problem doing that...but what fun is that, i want nothing handed to me and the challenge is what keeps me ticking. in a way it is worst than being a complete newbie because i have preconcieved ideas in a totally different area.

thank goodness you can't fill up you brain cause sometimes i feel like mine would be overflowing. LOL :blowup: