# Genetics



## Blackecho (Jun 30, 2008)

Ok, I have tried to put a guide together to help others to understand the genetics, let me know if it doesn't make sense:


























































Cheers
Hope that makes sense?


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## repkid (Nov 30, 2007)

WOW!

That actually REALLY helped!

Does this apply for leopard geckos aswell?

Very good! Sticky IMO.


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## Blackecho (Jun 30, 2008)

repkid said:


> WOW!
> 
> That actually REALLY helped!
> 
> ...


I know nothing at all about lizards sorry, maybe someone else can answer.


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## eeji (Feb 22, 2006)

good explaination 

...although from one of your illustrations, it looks like spider and pastel share the same locus

(forgive me if it does, I'm not well up on royal morphs! )


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## Blackecho (Jun 30, 2008)

eeji said:


> good explaination
> 
> ...although from one of your illustrations, it looks like spider and pastel share the same locus
> 
> (forgive me if it does, I'm not well up on royal morphs! )


Sorry, it wasn't supposed to look like that, I'll change the pic and edit the original post tomorrow.


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## MrMike (Jun 28, 2008)

repkid said:


> WOW!
> 
> That actually REALLY helped!
> 
> ...


Same theory for Leopard Gecko morphs yes.

Excellent post, I agree, sticky


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## Blackecho (Jun 30, 2008)

MrMike said:


> Same theory for Leopard Gecko morphs yes.
> 
> Excellent post, I agree, sticky


Thanks, I owe a lot of it to Ssthisto 2thumb for answering my PM's, then when I had it straight in my head just tried to make it as simple as I could.


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## bgfaith (Oct 7, 2008)

That should be made a post i have been trying to figure genetics out and that is so easy to understand. My god i feel relieved.


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## MrMike (Jun 28, 2008)

Blackecho said:


> Thanks, I owe a lot of it to Ssthisto 2thumb for answering my PM's, then when I had it straight in my head just tried to make it as simple as I could.


I'm sure this will help alot of people :2thumb:


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## Blackecho (Jun 30, 2008)

bgfaith said:


> That should be made a post i have been trying to figure genetics out and that is so easy to understand. My god i feel relieved.


Cheers.


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## Blackecho (Jun 30, 2008)

eeji said:


> good explaination
> 
> ...although from one of your illustrations, it looks like spider and pastel share the same locus


Sorted, cheers


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## toyah (Aug 24, 2006)

It's good but if you're getting down to that level of illustration I'd probably talk in terms of alleles instead of genes, as that could prove confusing in future for anyone learning from that.


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## Blackecho (Jun 30, 2008)

toyah said:


> It's good but if you're getting down to that level of illustration I'd probably talk in terms of alleles instead of genes, as that could prove confusing in future for anyone learning from that.


Thanks Toyah, will look into that.


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## Michelle G (Feb 27, 2008)

Helps me lots.....always makes more sense whien you look at it in diagram form! Thanks


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## paulh (Sep 19, 2007)

The main problem that I see is that there are two genes per locus but only one strand of DNA. Each chromosome has one strand of DNA, and each chromosome has only one member of a gene pair. In other words, the pastel mutant gene is on one chromosome, and the normal version of the pastel mutant gene is on a different chromosome. When forming sperm and eggs, the chromosomes pair up, and one member of the pair winds up in half of the sperm or eggs and the other member of the pair winds up in the rest of the sperm or eggs.

Alleles and genes are not exact synonyms. Pastel, spider, albino, and their normal versions are genes. Alleles are genes that share the same locus. So pastel and its normal version are alleles, but pastel and spider are not alleles.


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## paulh (Sep 19, 2007)

Another point. Humans have 23 pairs of chromosomes. Corn snakes have 18 pairs of chromosomes. I don't know how many pairs of chromosomes a royal python has off hand, but it's probably similar to the corn snake. Which means that there is a good chance that the pastel and spider loci aren't even in the same pair of chromosomes.


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## Blackecho (Jun 30, 2008)

I take your points Paul, thanks. Was just trying to keep it as simple as possible, I think it gets the main points across.


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## paulh (Sep 19, 2007)

Simple is good, as long as it is not simplified down to wrong. In my opinion, simplifying to one strand of DNA without mentioning that there are actually two strands qualifies as wrong.

Here are some more items to consider.

The Dominant and Codominant sections have headings, but the Recessive section does not. By the way, I follow King & Stansfield's Dictionary of Genetics in spelling "codominant" without a hyphen.

In my opinion, there ought to be formal definitions for "homozygous", "heterozygous", and "normal".

Homozygous = the two genes in a gene pair are the same.

Heterozygous = the two genes in a gene pair are not the same.

Normal = 1. the most common appearance in the wild. 2.The gene that is most common in the wild for each locus. 3. The gene that is the standard of comparison for each locus. Synonym = wild type.

Breeding 1 and 3 involve two loci, while Breeding 2 is a one-locus problem. In my opinion, people should learn to do a one-locus problem before going to a two-locus problem. Breeding 2's offspring column just has the phenotypes without putting in the genes, which I think is confusing to the reader.

I don't understand how the Parent 1, Parent 2 chart works in Breeding 1 and 3. I agree with the results; I just don't understand how they were arrived at. And if it confuses me, I'd expect the average person to be totally lost.


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## cervantes (Apr 24, 2008)

The main problem I had was a melting of my brain at spider.......................................................................................................................:bash::bash::bash:


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## intravenous (Dec 20, 2006)

paulh said:


> The main problem that I see is that there are two genes per locus but only one strand of DNA. Each chromosome has one strand of DNA, and each chromosome has only one member of a gene pair. In other words, the pastel mutant gene is on one chromosome, and the normal version of the pastel mutant gene is on a different chromosome. When forming sperm and eggs, the chromosomes pair up, and one member of the pair winds up in half of the sperm or eggs and the other member of the pair winds up in the rest of the sperm or eggs.


I agree with Paul that this is very important point...I know you want to keep the illustration basic but by doing it the way you have it might confuse people even more about how the genes get passed on and distributed to the offspring?


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## bladeblaster (Sep 30, 2008)

it is a very complex subject, hence why most people who understand genetics fully are doctorate level or higher. Or have been into breeding for decades.

Personally I think Blackecho has done an excellent job of making an understandable rough guide. For most people reading this PaulH has confused the hell out of them. It may not be entirely correct but it gets the point across to a level that is more than sufficient for most people.


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## Blackecho (Jun 30, 2008)

bladeblaster said:


> Personally I think Blackecho has done an excellent job of making an understandable rough guide.


Cheers mate, that's all it is, a rough guide. If people want to go into more detail feel free to add.


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## MarshallDavies (Sep 24, 2008)

great work *blackecho*! i can see very clearly what you mean, and i can aslo see it is meant to be a basic guide only. not to say *paulh*'s opinions aren't valid - just far more advanced than needs be for anyone who this thread is aimed at!

this thread goes a long way towards clearing up the confusion a lot of people will experience when starting out in genetics, and hey, with this under their belt maybe they'll delve deeper...

it's like saying you need to understand the delicate intricasies of advanced mathematics in order to do long division!

:2thumb:


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## paulh (Sep 19, 2007)

Here's approximately what I had in mind for the illustrations.

<img src="http://pholland.public.iastate.edu/Pix/chromosome_pair.png" alt="Chromosome pair" />


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## paulh (Sep 19, 2007)

The graphic didn't display.  Sorry about that.


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## paulh (Sep 19, 2007)

Trying one more time.


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## MarshallDavies (Sep 24, 2008)

a-ha! now i see what you mean too. maybe you should combine forces and _really_ spread some education...


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## bladeblaster (Sep 30, 2008)

MarshallDavies said:


> a-ha! now i see what you mean too. maybe you should combine forces and _really_ spread some education...


 
Great idea, you 2 should do a whole series :notworthy:


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## Blackecho (Jun 30, 2008)

paulh said:


> Trying one more time.


Ok, I'll have a play later and split them up.


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## TroJon (Aug 20, 2009)

Think the images fail to work.


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## Blackecho (Jun 30, 2008)

Sorry, moved them on Photobucket:



















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*I never did get round to fine tuning them.


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## Blackecho (Jun 30, 2008)

Updated Images (Thanks Paul)


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