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If a spider is considered a dominant mutation does that mean that a spider X normal would produce 100% spiders?

50% Spiders, 50% Normals.

It has yet to be proven whether a Spider from a Spider X Spider breeding is in fact a Super Spider and that it does in fact produce 100% Spiders from a Spider to normal breeding.

MJ
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To begin with, I have to say that I cannot answer your question with a simple "yes" or "no". Let's say that you asked the question "If a brick is flammable, does that mean that I could light it with a match?".
I could say "Yes...you probably could light it with a match". The problem with this answer is that you might interpret it to mean that I have just said you can light a brick with a match. I didn't. What I said was that if a brick was flammable you probably could light it with a match. So...you go and tell all of your buddies that "Renaissance said that I can light a brick with a match"...which is incorrect.
I could answer your question by saying "No...you cannot light a brick with a match". Although this is a correct statement, based upon your question stating "If a brick is flammable...", I haven't really answered the question that you asked because my answer did not assume that a brick was flammable.

So, what I am going to do is to attempt to explain why I cannot give a "yes" or "no" answer to your question. I hope that by the time I am done you will not only understand the dichotomy of your question, but that you will also have enough information that you will know the answer that you are looking for.

For the following discussion, I am going to use the term "morph X" to represent a trait that is dominant to the "normal" (wild-type) trait...

Morph X has two possible alternatives:
- Heterozygous
- Homozygous

The heterozygous form of morph X when bred to "normals" should produce (on average) half of the litter that are morph X and half of the litter that are "normals". The offspring that are morph X will be the heterozygous form of morph X.

The homozygous form of morph X when bred to "normals" should always produce an entire litter that are morph X. These offspring will all be the heterozygous form of morph X.

The heterozygous form of morph X when bred to the heterozygous form of morph X should produce (on average) three quarters of the litter that are morph X and one quarter of the litter that are "normals". Of the offspring that are morph X, 1 out of 3 should (on average) be the homozygous form of morph X, the other 2 out of 3 should (on average) be the heterozygous form of morph X. Since we are dealing with a dominant trait, there is no way to visually distinguish the homozygous animals from the heterozygous animals...the only way to distinguish them is through future breeding results.

The homozygous form of morph X when bred to the homozygous form of morph X should always produce an entire litter that are morph X. These offspring will all be the homozygous form of morph X.

So...to answer your question as asked...
If Spider is a dominant morph, breeding Spider to "normal" would have different results depending upon whether the Spider was the heterozygous or homozygous form of a Spider.
A heterozygous Spider when bred to "normals" should produce (on average) litters where half of the litter are heterozygous Spiders and half of the litter are "normals".
A homozygous Spider when bred to "normals" should produce litters where the entire litter are heterozygous Spiders.

The reason that I say "if Spider is a dominant morph" is that there is currently insufficient breeding data to state with any degree of certainty that Spider is in fact dominant. We do know for a fact that breeding a Spider to a "normal" will produce (on average) litters where half of the offspring are Spiders and half of the offspring are "normals".

In order to be able to state with a high degree of confidence exactly what genetic inheritance is involved, sometimes many, many seasons of breeding results must be achieved and considered. At various stages along the path to reaching a conclusion as to what the genetics of a particular morph really are, certain possibilities may appear to be more obvious than others. For example, we are very confident that Spiders are not a recessive trait.

In some situations, certain morphs may have genetic inheritance labels assigned to them...only for it to be subsequently discovered that this was a premature classification that was incorrect. A good example of this is the current controversy regarding Fire Balls and Black-Eyed Leucistics. Some folks have (prematurely, not only in my opinion but also in the opinion of many others) declared with absolute certainty that the Black-Eyed Leucistic trait is a codominant trait, and that Fire Balls are the visible hets. of this trait. Forgetting for one moment whether the term codominant or incomplete dominant is more appropriate, it is too early to know with certainty whether in fact the Black-Eyed Leucistic trait is a codominant trait (with the Fire Balls being the visible hets.) or a recessive trait that occurs and inherits independently from the Fire Ball trait. It may be either. It is impossible to know for sure based upon the breeding results that have been obtained to date. The Black-Eyed Leucistic trait may be codominant or incomplete dominant...it may be recessive. We can not know for certain until further breeding results have been achieved.

A good historical example of the changing of morph classifications is Salmon boas. In the early days of Salmon boas, the Salmon trait was believed to be and marketed as recessive. The downside to this was that some folks purchased "het." Salmons, only to subsequently discover that they had purchased "normals".

Just because a particular genetic inheritance is assigned to a morph and then the genetic inheritance is subsequently discovered to be something different, do not assume that the breeder of that morph deliberately set out to mislead people. There are many reasons why breeders sometimes rush to prematurely classify the inheritance of a morph. Here are a couple that come to mind:
- They may not have a complete and thorough understanding of the genetic terminology.
- They may not have a complete and thorough understanding of the breeding combinations and results necessary to prove with any degree of certainty exactly what genetic inheritance is involved with a morph.
- Competitive market forces may cause them to rush to judgement before they really can be certain.
- Sometimes breeders are eager to share their current beliefs about the new morph. In an eagerness to share their knowledge with the ball python community, the breeders publish what they currently believe is most likely to be the genetic inheritance. Unfortunately, they do not make it clear that this is their "best guess"...not "guaranteed".
- Sometimes the ball python community just has to have a label to hang on the morph. Is it recessive? Is it codominant?. We want to know!!! In response to this demand, the breeders sometimes publish what they currently believe is most likely to be the genetic inheritance. Unfortunately, they do not always make it clear that this is their "best guess"...not "guaranteed".

Confusion sometimes arises when a breeder's previously published "best guess" turns out to be wrong. Unfortunately, the "best guess" was understood by the ball python community to be a "guarantee"...and not a "best guess".

I'm sure that this is w-a-y more information than you really expected or wanted to hear, but it is impossible to answer the question that you asked with a simple "yes" or a "no" since Spiders have not been proven to be dominant.
Spiders were once "classified" as codominant.
They were subsequently "reclassified" as incomplete dominant.
They were subsequently "reclassified" as dominant.
Spiders may be dominant...they may not...further breeding results are required.

I hope this helps.

Nigel... quick question...

First off... I totally agree (which doesn't really matter because you gave scientific explanations NOT opinions)!

Here it is... We know that Spiders are NOT Recessive... we are pretty sure that they are NOT Co-Dominant or Incomplete dominant... so if they AREN'T Dominant... then what can they be??

I have not really read into or heard of any explanations in animal genetics that explains any other types of inheritances??

Just curious...
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Sean Bradley
Owner : EbN
www.ExoticsByNature.com
www.BallPythonMorphs.com
www.CornSnakeMorphs.com

I think what Nigel's saying is that the mutation is either incomplete dominant or dominant. Though many spider X spider clutches have been produced with no super phenotype, it is still theoretically possible that a homozygous form wasn't produced. The only definitive proof of dominance will be a spider X normal clutch consisting entirely of spiders.

Jake

Many...

As far as I know, there have already been a couple of clutches produced from Spider to "normal" breedings where the entire clutch has been Spiders. Repeated breedings of the particular Spider(s) involved, however, did not produce whole clutches of Spiders from every breeding.

For example, if a Spider male was bred to some "normal" females and 3 clutches were produced that consisted entirely of Spiders, we might surmise that Spider could be a dominant morph and the Spider male could be a homozygous Spider. If a single subsequent breeding of that Spider male to a "normal" female produced a clutch that was not all Spiders, we could reasonably conclude that this particular Spider male was not a homozygous Spider. Although this particular clutch (not all Spiders) would provide additional information that the male was not a homozygous Spider, it would not in and of itself provide sufficient additional information to conclude whether or not Spiders were dominant.

It's a little like saying that there are no Volkswagen Beetles in the World that are blue...
If we see one blue Volkswagen Beetle, we know that this statement is false...
If we do not see a blue Volkswagen Beetle, we have to keep looking until we have examined every Volkswagen Beetle. Once we have examined every one and found that none are blue, then we can say with certainty that the statement is true.

Some things are proven or disproven by exlusionary methods.
Some things are proven or disproven by inclusionary methods.
Sometimes other methods are needed.

I frequently suffer from the "Duhs", too...

Not sure if I'm homozygous Duh or heterozygous Duh...
More breeding data is needed...

LOL...

how would if a spider produced multiple clutches that were all spiders prove it was dominant?
a plain pastel can produce multiple clutches that were all pastels.
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0.1 "Tremper" looking Albino Leopard gecko (Lex)
0.0.1 normal ball python (felix)
1.1 Feral cats that we adopted (Fuzzy, and Bear)

I believe that Pastels have been proven co-dominate...could be wrong. If you get a clutch from Pastel to Normal and 100% of the offspring are Pastel, I believe that is just lucky.

The one thing that I understood for sure out of his reply is that it is impossible to 100% prove dominance. But if you could produce clutches from Spider to Normal and 100% of the offspring were Spider....and you repeated this breeding and got the same 100% results....each time you achieved these results would bring you closer to proving the gene is dominate.

If you could reproduce these results 100 times, you could still not technically say it is proven though, because you cannot predict future results. Even though it is HIGHLY unlikely that a normal offspring could be created, the possibility is still minutely there. And if even a singal Normal offspring was created then it would disprove the theory of dominance.

Jake,

Here is my thought on that view... theorectically the Super could have been missed but how likely is that?? I would like to know exactly how many Spider x Spider eggs have hatched with no noticeable Super?? Your odds, if Inc. or Co-Dominant is 1 in 4... while this is just statistics at their most verifiable... if there have been 20+ Spider x Spider eggs hatched to date with no visible Super then wouldn't that mean that there is none?? Unless it is perhaps a "lethal-gene" in which the Super Spider died upon conception?? Perhaps was laid as a slug?? Couldn't be absorbed into the female's system could it? Maybe it could as long as the conception takes place previous to ovulation (which I believe it does?? correct??)

Basically... its NOT reccessive! It's not a Inc or Co-Dominant unless there is a Super/Homozygous (unless the "lethal gene" thing is true) that is visually discernable from a Het. Finally... if it is NOT Dominant... what other possibilities are there?

What do you all think of the "lethal gene" thing??

Thanks,
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Sean Bradley
Owner : EbN
www.ExoticsByNature.com
www.BallPythonMorphs.com
www.CornSnakeMorphs.com

From what I've heard, it's pretty safe to say that spider is a dominant mutation. Like Nigel's saying, though, this label could be changed in the future.

As for the lethal gene theory, I could see this happening. The gene that is mutated in the spider morph could code for some enzyme that was not only necessary for correct (wild-type) pattern formation, but also necessary for some vital metabolic process. Perhaps in the heterozygous form, enough amounts of the functional (wild-type) enzyme would be made to perform this metabolic function, yet not enough would be made for completely normal (wild-type) pattern.

Jake

Can re-absorption take place after fertilization? I never thought about it before, but if that does occur, that’s amazing! Does anyone know for sure?

I think the lethal allele idea is a valid one, but I am a curious about how common lethal alleles are. Maybe someone has an idea about how often it actually occurs in other species? Applied to ball pythons the number may be a little higher than the normal of course, but is it likely to happen? At work, debugging computer code, I always tend to favor the "KISS" theory ... "Keep It Simple Stupid" ... but, I would be interested in slug data for breeding spider to spider? (Unless re-absorption after fertilization is possible, then proving or disproving lethal alleles would be moot right?)

(Smoke coming out of my ears)

-adam

Dominant Spot in Syrian Hamsters appears to be a lethal (actually co-dominant) gene. I suppose it took a while to figure this out (or at least a few generations, a lot quicker with hamsters than ball pythons) but from what I read it sounds like the evidence was that no one ever proved a homozygous dominant spot and dominant spot X dominant spot litters tended to only average 3/4 size.

I'm not sure if the clutch size analysis would work in ball pythons as it's harder to predict an average size (I use the pre-lay weight in grams divided by 330) and without knowing a lot more about the egg creation process and when the embryo might die I'm not sure if the number would be effected anyway. Unless it works out that the homozygous matchups make it as far as eggs that can be counted to see if spider X spider consistently have about 1/4 more unhatched eggs it will have to be "proved" by the weight of never proving one homozygous spider over a long period of time. But as someone pointed out, you can't ever be 100% sure of proving something by it’s absence so at some point you just have to decide that there is enough evidence to call it one way or the other.

Do you know if the litters were just 3/4 size or if there were actual aborted fetuses found? i've read that the scientist that first described lethal alleles (Cuenot i think???) also got 3/4 litter sizes when breeding yellow dominant mice together. Although, he notes the presence of aborted fetuses to account for the missing 1/4. i know that lethal alleles can become lethal at any point during an organisms lifetime, but if there were a lethal allele in a ball python morph i wonder if there would consistently be a slug or snake dead in an egg with every hetero to hetero clutch (assuming that’s how the lethal allele was manifested)? Or, will the genetics gurus tell me that i am over simplifying things?

lethal alleles are a neat idea, but IMO probably not what’s going on here (although i hope i'm wrong because it would be kewl to own a snake with a "lethal" allele ... LOL).

-adam

I found this one link that indicates that the homozygous dominant spot Syrian hamsters are re-absorbed. I suppose it might be hard to tell though unless you where watching as they where born.

Other pages had interesting notes on the subject. One pointed out that the ratio of dominant spots to normals in the litters from dominant spot X dominant spot is 2:3 rather than the expected 3:4 if it where dominant and not lethal (this is because the expected 1:4 homozygous dominant spot don't exist). Another pointed out that this gene is dominant in respect to coat color but recessive in respect to viability. I prefer to think of it as co-dominant (the homozygous is different than the heterozygous in that it's dead and the heterozygous is different than the normal) but it's an interesting idea that different aspects of the same mutation could be classified with different inheritance.

I’m actually hoping that Spider is completely dominant and that a homozygous one will be proven. It’s not the end of the world if it is lethal homozygous either, I suspect it would then be used like the dominant spot gene in hamsters – generally on one side only of a pair. Just a little more incentive for all the neat spider crosses.
Dominant Spot Hamster Page

>Although, he notes the presence of aborted fetuses to account for the missing 1/4. i know that lethal alleles can become lethal at any point during an organisms lifetime, but if there

I may not know much about the genetics of Ball Pythons, but I consider myself something of a lay-expert on mouse genes. My vacation reading this week has been the "coat colors of mice" by Silvers... a VERY technical book.

As far as Silvers states, homozygous dominant yellow mice lack some specific ingredient to implant in the uterine wall, therefore they never implant, the mouse re-absorbs the fetus (which at this stage is merely a microscopic clump of cells), and never "aborts" the fetus.

As far as lethal genes, there are quite a large number of them within the mouse fancy, and even more varieties produced through irradiation. There is dominant white spotting which is also lethal when homozygous. In that case the animals actually make it to birth, and usually die of anemia in the first three weeks of life... some do live, are half size, black eyed white, and sterile. In my mouse colonies I have dominant yellow, Viable dominant yellow, and recessive yellow, which on first inspection are all phenotypically identical. My record keeping is not perfect, and with a recent move, they got all mixed up. Now I've had to try to use litter size to figure out which ones are lethal dominant yellow, which are viable, and which are recessive. So far no luck.

I have to say I have enjoyed the discussion so far. The genetics of ball pythons will probably always be hypothetical to me, but I look forward to continuing my learning curve.
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~Sasheena

I didn't have a clear picture as to whether the aborted fetuses were actually passed or re-absorbed, that helps a lot! Seems like re-absorption is actually likely then? Doesn't bode well for ever actually proving a lethal allele in a ball python mutation unless someone is going to start cutting open gravid females (shutter)!!!

I agree with Randy though and have my fingers crossed for a dominant homozygous spider. How kewl would it be to see a big 10 egg clutch of all baby spiders peeking out of the eggs!!!

Thanks Sasheena, that helped a lot!

-adam

There will be plenty of fun figuring out ball pythons for any of our life times I think. The rodents breed so much quicker so the snakes will take lots more patience.

Nothing new but I did create my own line of calico hamsters with separate sources for black (recessive), banded (dominant), and yellow (sex linked) and it all only took about a year. When will we see the first triple mutant ball pythons, 2010 maybe?

Whitesnake rocks!!! Cool hamster too ... LOL

-adam

Thank you...

Thank God his simple question concerned the Spider's trait............and not the evolution of Earth...........jk

Tom Murphy
PS......I thought you were working on a web-site......where's it at?

Please don't mention the w-e-b s-i-t-e...
I should be further ahead with it...
But I'm not...
You're going to get me into trouble with my better half...

The way you ramble on here sometimes......I couldn't even fathom the rambling on your own site........a WHOLE lot of links for just ONE morph.............

But I'm sure your better half is used to it.......so she understands the time (your time) involved.