A Lesson in Basic Genetics

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