A Lesson in Basic Genetics

Is normal dominate? or what is it??? how come (not het. for anything recessive) ALL spiders are het. normal, but NO normal can be het. spider?? why does the animal look the mutated gene if it has normal and that mutaint gene in it? it acts recssive when combined with a dominate or co. dom. morph right? but then when mixed with a real recessive morph it acts dominate.

If you don't understand what im saying i'll use an example.. okay so use spider. a spider has 2 genes effecting its skin right: 1 spider gene, 1 normal gene..okay so why does it look spider if normal isnt recessive its supposdly dominate isnt it? (or maybey it isnt, maybey i missed something major??) okay and it wont mix to make a new morph, like combining a pinstripe and a spider will mix to make a spinner. but then when you have lets say a normal het. pied, it has: 1 pied gene, 1 normal gene right? okay so then in this case it acts dom. or co. dom.????!?!??!?!??!?!


maybey im thinking to hard but this has really been buggin me and I need to know and cant find any where that talks about normals here or anywhere!
if someone wants to respond and clear me up it'd make my day thanks!

I'm certainly confused, :P

Don't try and think of normal as dominant or codominant to other morphs.

Think of what the morph gene does in the heterozygous ( only one copy in the animal ) and homozygous ( two copies in the animal ) animals looks.

Spider is a really bad choice for this as nobody has a proven homozygous example so if you don't mind I will use pinstripe - where there is only a rumoured homozygous example. :rofl: :rofl:

Dominant:

One copy of the gene (hetrozygous ) makes a visually distinct animal from the normal wild type. Two copies of the gene ( homozygous ) look the same as the single copy hetrozygous animal. So there is no way to see if a pinstripe is het or homo visually. But you can see it is not a normal in both those forms.

Co-dominant:

This is a tricky one only because ball-python breders are using the wrong term - I think it should really be incomplete dominant if memory serves.

The heterozygous animal is visually different than the wild type but the homozygous animal looks different again.

So a pastel looks different to a normal and a super pastel looks different to both.

Recessive:

A heterozygous animal looks exactly the same as a normal animal that does not have any copies of the gene at all. You cannot look at the animal and be sure it has the gene for this type of morph.

But the homozygous animal looks visually different to a normal wild type.

People are always looking for subtle "markers" that can be used to identify heterozygous animals - but if they ever find a reliable one that morph would no longer be considered recessive at that point but co-dominant instead. :rolleyes:

So a normal and a het pied look the same but the homozygous pied animal would look noticeably different.

You can't really use any of these terms for wild type in any usefull way so it's best not to try.

If that makes sense.


dr del

This is pretty old but I just found it and wanted to say its outstanding.

Is there any source specific to Retics to play around with the percentages of possiblities? I understand completely on single morphs but I have double and triple morphs that I want to hook up and want to see what outcomes may be. Thanks

can someone PLEASE tell me how to get to the classified ads section on this site ? lol IM NEW ! lol thanks so much.

http://ball-pythons.net/forums/forum...tion-or-Wanted


I don't know that I'd call it a "classified section" but it's in the business section on the forum list.

Joe Ellis was teaching me some of this today. Were still working out the Leopard breeding thing. Your layout makes it a lot easyer to understand, going to print and put up in my snake room. If thats ok to do?

This si AMAZING for noobs like myslef. Hahahaha! Thanx a lot:D

Wow, I've been reading through this thread because I want to purchase a pair of pastels in a couple months and eventually breed them. This thread has taught me a lot and I will definitely be doing some more research to fill in some of the blanks! Thank you to all who have contributed.

Does anyone know of an extensive list of which morphs are recessive, etc? I found something basic on NERD's site, but I didn't see a list of dominant or co-dominant morphs. Thanks!

Thanks for the good run down

Very interesting, and well done. I absolutely hated this class in college.

Thank You

This was a good read. I will need to print and file for future for me.

:)

HOW DOES ALL THIS WORK?

Picture a pair of shoestrings. Lay them down side-by-side. Now picture them with colored balls stuck to each of them:

-o-o-o-o-o-o-o-o-

-o-o-o-o-o-o-o-o-

Each -o-o-o- strand represents the double helix DNA molecule in a single chromosome.

Each dot represents a single gene or allele.

The dot in one chromosome and the corresponding dot in the same location in the other chromosome represent a pair of genes/alleles located at a specific locus.

Each pair of genes has a different “job” in determining the look of an animal. It takes many different pairs of genes, each doing a specific job, just to determine the overall pattern and colors of a snake.

When two animals mate and create young, each parent contributes one chromosome (including its double helix DNA molecule) from each pair of chromosomes to the offspring. Therefore, one gene from each parental pair of genes creates a whole new set of pairs in the offspring. For instance, the red dots…one red dot from the mom and one red dot from the dad. Always. One yellow dot from the mom, and one yellow dot from the dad.

Spider and Pinstripe should not be considered dominate, since there is a super fom and that super fom is lethal. If it was as simple as dominate and we assume that the homozygous form looks the same, we would be able to prove out homozygous individuals by the production of 100% spider or pinstripe offspring. And by cornells defintion of co-dominate we can safely put them under this catagory by listing the co-dom as lethal homozygous. One last statement - If Spider was true dominant, it would block expression of any other gene related to pattern, but as we see with other traits being visually observed when combined with spider, we again can assume that it is co-dominate, a trait that effects the phenotype without masking other genes whos traits can also be expressed :-).

Very good post though for the majority of BP people!

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Originally Posted by reptileexperts

Spider and Pinstripe should not be considered dominate, since there is a super fom and that super fom is lethal. If it was as simple as dominate and we assume that the homozygous form looks the same, we would be able to prove out homozygous individuals by the production of 100% spider or pinstripe offspring. And by cornells defintion of co-dominate we can safely put them under this catagory by listing the co-dom as lethal homozygous. One last statement - If Spider was true dominant, it would block expression of any other gene related to pattern, but as we see with other traits being visually observed when combined with spider, we again can assume that it is co-dominate, a trait that effects the phenotype without masking other genes whos traits can also be expressed :-).

Very good post though for the majority of BP people!

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what is your evidence to back up the claim that the spider and pinstripe mutations are not dominant? not only is there no super, but to my knowledge there is no proof that the homozygous expression of either gene yields anything less than viable offspring. it's only secondhand, but I have heard precisely the opposite. do you have any firsthand information to the contrary?

by your definition, the only possible way for a mutation to be classified as dominant would be if it precludes the expression of any other co-dominant morphs. champagnes have a tendency to swallow up other mutations and overwhelm patterns. are they dominant? genetic black backs and reduced/banded snakes often pass on their patterns but there's no way you would classify those types of animals as co-dominant (or incomplete dominant for that matter).

why chime in on this post, again meant to assist newcomers with a rudimentary understanding of ball python genetics, with erroneous information over four years after Judy was good enough to put it up?

Errorness? I'm not going to hound you with my background nor do I care to partake in an argument on the interweb :-) However, see the other thread that is going on in regard to dominant traits.

The fact that noone has a spider or pinstripe that is proven homozygous, is evidence of this. The case for dominance is the exclusion of any other gene present. Co-domance is just what it says - allowing expression of multiple mutations on differnt loci, and in rare cases the same loci, but when its on the same loci it's more leaned toward incomplete dominance where the super form is the actual meant expression of that gene (my example being pastel).

Where is the proof for it? The fact that NO ONE has produced a homozygous spider or pinstripe is the proof, or at least the presented evidence I offer. If somone had a homozygous it would be known as all of its young would contain the dominate gene (not trait) allowing for expression of the trait.

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Originally Posted by reptileexperts

Errorness? I'm not going to hound you with my background nor do I care to partake in an argument on the interweb :-) However, see the other thread that is going on in regard to dominant traits.

The fact that noone has a spider or pinstripe that is proven homozygous, is evidence of this. The case for dominance is the exclusion of any other gene present. Co-domance is just what it says - allowing expression of multiple mutations on differnt loci, and in rare cases the same loci, but when its on the same loci it's more leaned toward incomplete dominance where the super form is the actual meant expression of that gene (my example being pastel).

Where is the proof for it? The fact that NO ONE has produced a homozygous spider or pinstripe is the proof, or at least the presented evidence I offer. If somone had a homozygous it would be known as all of its young would contain the dominate gene (not trait) allowing for expression of the trait.

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Dominant/codominant/recessive describe the relationship of genes at a single locus. Multiple loci gets into epistasis and gene interactions.

I've looked at the thread on dominant traits. Absence of evidence is not evidence of absence.

What is the biochemical data indicating that pastel is an incomplete dominant mutant gene and not a codominant mutant gene? Let's take that question to PM, though.

Thank you! This has been a tremendous help.

YOU ROCK OUT LOUD FOR THIS POST!!!!!!!!!!!!!!

I have a 10 yr old who's into science and loves the morphs we already have, and this helps me show her how it works, hell it helps me too...lol..

I love the part about the spiders also because of the "taboo" behind them.......I love talking to my local and virtual "herpetologist" community about the crazy things they come across....LOL......I see all of you/us as pioneers, and explores of our passion. Gene's are the key codes to life and the more we find out the more doors we open, into new understanding. Endless possibilities, and the thought of producing or "PROVING" out something cool for all the herp community to enjoy!

good info but how do you get co dominant colours in the first place?

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Originally Posted by poultrytom

good info but how do you get co dominant colours in the first place?

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If you bother to research juuuuust a little you'll easily find that information, but eh I'll start you out:

I theorize that some ppl have gone all Faust-but-with-snakes and sold their soul to the devil to find and create all the hottest new morphs.

For the rest of us, they are originally found as wild caught snakes in Africa. Sometimes its already a wild morph, many have been found. Others times its breeding the wild caught snakes and discovering they carry some special genes that make hot snakes. Sometimes already gravid balls are collected wild and their eggs hatched, known as "captive hatched," usually they turn out normals, but sometimes its something cool. New morphs are discovered periodically. The morphs just occur, random mutated genes, no one is totally sure why. Balls are a bit like the rainbow of the animal world: all the same species, but sooooo many different paint jobs.

Just pick (base) morphs and research them, you can usually read about how that particular gene came to be. Albino was the first discovered.

Ok that was a ton of genetic info, but I'm curious as to whether when you breed an albino to an albino (neither are paradox) if a normal can pop out and what kind of het would it be?

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Originally Posted by tjohn310

Ok that was a ton of genetic info, but I'm curious as to whether when you breed an albino to an albino (neither are paradox) if a normal can pop out and what kind of het would it be?

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That isn't possible. Albino x Albino would give you all Albinos.

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Originally Posted by spitzu

That isn't possible. Albino x Albino would give you all Albinos.

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Thank you for clearing that up for me. I was just unsure if it could happen and what it would be called.

great job really helps a lot. I am trying to figure out a good combination to start of with. any idea's starting small but looking for something interesting.

I'm pretty positive that my brain just burst into flames.

Wow! Thanks so much for this! I've had ball pythons a while, but recently started learning more in depth to start trying to breed them & this broke things down so easily!!


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Hi, i'm newbie here. It's help me a lot :)

awesome and very helpful for alot of people in this hobby!:snake::snake::snake::snake::snake::snake::snake::snake::snake:

Thanks thanks thanks!!! While most of the basic genetics concepts I have worked to understand fairly well this she'd light on the parts that have been confusing. I know feel I have a much better handle on this.

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What a great post! Thank you so much. If I read that another few times it will begin to sink in. Now, off to the calculator...

Sharon

This was great thanks for having it out here. I still have a ways to go before I'm really comfortable with all the terms but I do have one question. What do the numbers next to the snakes in people's signatures signify? Example: 1.0 Spider Het Ghost or .01 Coral Glow. I've searched the forum but found nothing.

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Originally Posted by C2tcardin

This was great thanks for having it out here. I still have a ways to go before I'm really comfortable with all the terms but I do have one question. What do the numbers next to the snakes in people's signatures signify? Example: 1.0 Spider Het Ghost or .01 Coral Glow. I've searched the forum but found nothing.

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1.0 is a male and 0.1 is female, 1.1 means they have 1 male and 1 female. You can also have 0.0.1 the 1 in this example means unsexed. Hope that makes sense.

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Originally Posted by joebad976

1.0 is a male and 0.1 is female, 1.1 means they have 1 male and 1 female. You can also have 0.0.1 the 1 in this example means unsexed. Hope that makes sense.

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Perfect! Thanks so much.

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Originally Posted by eracer

I have the same question. Is the breeding for morphological changes producing mutations that negatively impact the overall robustness of the species? Or is there enough diversity within the existing gene pool that dilution will not be a problem?

We see these types of problems in dogs. Why not in snakes?

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Several things...

First of all, color 'morphs' are mutations - they may even be a problem for wild ball pythons (e.g. an all white snake may be easier for predators to find whereas we find it beautiful) - but not all 'mutations' are problematic (a 'mutation' is just a 'change' after all)

Secondly, when people want to produce reliable offspring, they tend to 'in-line' breed - mother to son, father to daughter, brother to sister, etc. This ensures the genes you WANT are in the gene pool. With wild caught mutations, this is a necessity to 'prove' the morph at all (if it's recessive), since usually only a single 'dinker' is discovered at a time.

Your concern about negative health impacts comes from the idea that inbreeding is bad. Here's where we enter a genetic grey zone (stay with me, this is where it gets super-interesting!).

Inbreeding is only dangerous if there are 'bad' mutations in the gene pool - usually 'bad' mutations are recessive, so if you only have 1 'bad' copy, you're okay.

If a male carries a single copy of a cool color mutation (let's say caramel) AND a 'bad' mutation (say, kinking), he may appear normal and eat/sleep/poop/breed fine. When we breed him to his own sister (also 'normal' and healthy), we get a low percent of caramel offspring and a low percent of kinked offspring. Importantly, these caramel and kinked kids MAY NOT BE the same offspring - it's all random... sometimes. Other times (as is the actual case with caramel), the 'bad' mutation (kinking) is "linked" (physically close on the chromosome) to the color mutation (caramel) - this means they go together more often than not. If you can get unrelated het caramels, the chance they will have the same 'bad' mutation drops (this is when people talk about combining 'different lines'), but it is still possible (depending on how far back their genetic independence goes, and wether there are multiple 'bad' alleles/loci at play - which seems the case in caramels).

So how can you tell if inbreeding is dangerous?

Well, mostly it has to do with the effective population size - in German Shepherds today, any two "unrelated" individuals (two from anywhere in the world) are genetically as related as full brother and sister (as determined by linkage disequilibrium and expected relatedness coefficients). This means they are EXTREMELY consistent for color, disposition, height, weight, etc. It also means German Shepherds have known health defects (prone to hip dysplasia, blood disorders, etc, etc).

Ball pythons haven't been selectively bred for many generations (ESPECIALLY compared to dogs - think 100,000 years) and there is still a constant influx of genes from wild populations (allowing ball python effective population size to stay relatively large). Your intuition about diversity is spot on!

The responsible thing to do is outcross as much as possible in any morphs with known heritable disorders and keep diligent records for everything else. With modern practices (even being able to talk to other breeders so easily), genetic bottlenecks are less likely and 'in-line' breeding can help make beautiful, docile, healthy pets.

One of the best things out there for intro genetics is called The Cartoon Guide to Genetics ( http://www.amazon.com/Cartoon-Guide-.../dp/0062730991 ) - we recommend it for all our interns when they first start (from high schoolers to college seniors) because it's SO MUCH BETTER than a text book!

I hope that helps!

Thanks, Judy, for posting this all those years ago!! Surely it's good to see that people are still reading and commenting on your post. :D This post made things clear for me, and was the starting point in my research on the bp morphs.

As we speak, I'm printing this post, along with some thumbnail pics of different morphs and Punnett squares, to use as a lesson and worksheet for my son's science notebook. He's been going crazy over bp morphs since we got our first bp, a Yellowbelly, three weeks ago. He's only 7, but to hear him go on and on about the colors and patterns is great! I love the way he says "Spinnerblast!"

What about the enchi and super genes. I have 5 morph balls (pastel-m, orange glow-f, lesser-f, spider-f, ghost-f) I ultimately want a Super Pastel Fireball Enchi love there colors and a Xantantic. But those two genes I don't understand.:confusd:

Hi, I just finished reading your thread and I have to say it really is awesome and has taught me A LOT but there is one thing that I'm not sure is correct. Ok so I'm confused by the 2 strands of DNA you use to represent each morph. Wouldn't it be better to represent the DNA for each morph as a helix instead of 2 strands? I thought that DNA was a helix and if it is then i'm not sure if your illustration is correct. The reason I say this is because if you combine the 2 strands the way you visualized them then it won't create a regular DNA helix. Realistically one strand would only have one gene per allele, it is only when you combine the other strand that you get the second parent gene which forms the helix. With your illustration it looks like you are trying to represent one strand as an entire DNA helix because you have the 2 gene dots which would only happen with a fully formed helix. Idk if I'm right about all this or if i'm just totally confused. Anyways, I would appreciate if you got back to me on it just so I can make sure I'm understanding the basics correctly. Thanks again for the awesome guide.

-Sean

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Each strand represents one of the two DNA strands all animals have.

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This part would be better read as both strands

Think of it as a ladder. Each rung devided in half.

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Alright I made this picture using paint (please excuse my poor artistic skills) of what I'm talking about. Tell me if this is right because this is how I imagine a DNA helix would look. If this is correct then idk how OP's illustrations could be correct also.http://ball-pythons.net/gallery/file.../dna_helix.png

This isn't a scientifically accurate guide at all, it is information to understand inheritance, the DNA structure plays very little role in what we deal with, within the hobby. However each shoestring in her example should be stated to represent both sides of the DNA, not just one.

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Originally Posted by Mysnakeislong

Hi, I just finished reading your thread and I have to say it really is awesome and has taught me A LOT but there is one thing that I'm not sure is correct. Ok so I'm confused by the 2 strands of DNA you use to represent each morph. Wouldn't it be better to represent the DNA for each morph as a helix instead of 2 strands? I thought that DNA was a helix and if it is then i'm not sure if your illustration is correct. The reason I say this is because if you combine the 2 strands the way you visualized them then it won't create a regular DNA helix. Realistically one strand would only have one gene per allele, it is only when you combine the other strand that you get the second parent gene which forms the helix. With your illustration it looks like you are trying to represent one strand as an entire DNA helix because you have the 2 gene dots which would only happen with a fully formed helix. Idk if I'm right about all this or if i'm just totally confused. Anyways, I would appreciate if you got back to me on it just so I can make sure I'm understanding the basics correctly. Thanks again for the awesome guide.

-Sean

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You are right; that illustration is not correct. IMO, this is less pretty but more correct.

Pair of homologous chromosomes
-o-o-A-o-o-o-B-o-o-o- = the double helix of DNA in one chromosome. Each o represents a gene.

-o-o-a-o-o-o-b-o-o-o- = the double helix of DNA in the other chromosome. Each o represents a gene.

By the way, alleles have different DNA sequences but the same location in a chromosome. In my pair of chromosomes, A and a are alleles because they have the same location. B and b are also alleles. A and b are not alleles, and neither are a and B. A, a, B, and b are all genes.

Link: http://ghr.nlm.nih.gov/handbook
The link is to the Genetics Home Reference, which can be freely downloaded. The first chapter has material about genes and chromosomes and DNA. It may be helpful. By the way, the Home Reference shows a chromosome as X-shaped because that is the stage that is visible. Each X-shaped chromosome is dividing and will eventually become 2 rod-shaped chromosomes before unwinding into an invisible thread.

Images of a DNA double helix.

http://photobucket.com/images/dna

:popcorn: yussss

Here's a resource to get your feet wet in genetics. The video helps put things into context.

http://learn.genetics.utah.edu/

I didn't read back 10 pages, but I hope someone corrected the codominant thing, since there are no codominant ball python mutations that we know of.
We work with incomplete dominant traits, VERY different from codominant traits.

Incomplete dominance is a blending of traits.
When you make a pastel mojave the two traits blend to make a yellowed out mojave.
If these two mutations were codominant parts of the snake would look like a pastel and parts would look like a mojave. They wouldn't blend together like incomplete dominant traits.

Jerry

Different texts have different definitions of codominant and incomplete dominant. I know of three that are more or less accepted.

The oldest definition is that in intermediate dominance, the heterozygote is more or less intermediate in appearance between the two homozygotes. For example, in many flowers the heterozygote produces pink flowers, one homozygote has red flowers, and the other homozygote has white flowers. In codominance, the heterozygote has some areas that look like one homozygote and other areas that look like the other homozygote. For example, the human A blood type, B blood type, and AB blood type.

If we use the traditional definition, we also need to add a third category--overdominance. The heterozygote's appearance is outside the range of the two homozygotes.

Here is the most recent definition that I have seen. In incomplete dominance, one allele has a functional product and the other allele does not. This produces a blend--pink flowers instead of white or red flowers. In codominance, both alleles produce functional products. If the test is sensitive enough, both alleles can be detected. For example, in the human AB blood type, both A and B antigens occur on the surface of the same red blood cell and can be detected. In less sensitive tests, a blending can occur as in the Tonkinese cat. Both the Burmese and Siamese alleles produce melanin, but different amounts. The Tonkinese cat has one of each allele and produces an amount of melanin roughly intermediate between that of the Burmese and Siamese cats.

The third definition basically says that nobody has figured out whether only one or both alleles have a functional product. Until that is figured out, call the two alleles codominant to each other, because "codominant" requires fewer keystrokes to type than "incomplete dominant". And define codominance as each of the three possible genotypes producing its own characteristic appearance.

IMO, a five part classification scheme (dominant, recessive, incomplete dominant, codominant, overdominant) is too inconvenient for newbies and most breeders.

Does the pastel situation parallel the Burmese cat or the pink flower? I don't know, and I don't think that anyone knows. So the second definition cannot be used with accuracy. And do breeders care about the number of functional gene products? I've bred a lot of birds, and the main thing I wanted to know was the identity of the bird's genes.

That leaves the third definition. There was a paper in Bioscience magazine in 1995 (Three neglected advances in classical genetics) where the author stated he had used that definition successfully in introductory genetics courses.

There are no codominant traits in ball pythons.

Pastel + mojave makes pastave where the two colors blend together.
If they were codominant there would be parts of the snake looking like a pastel and parts looking like a mojave.