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PaulG
Captivebred Colonel
Joined: 26 Jan 2007
Posts: 3996
Location: North West
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 Posted: Sat Aug 18, 2007 12:29 am Post subject: |
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very informative post eggman!
I have kinda grasped this cus im always readin bout them! lol
but yer its helped alot and im sure it will help a lot more people!
Paul
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Phil1988
Captivebred Communist
Joined: 25 Jan 2007
Posts: 1589
Location: Manchester
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| Posted: Sat Aug 18, 2007 12:57 am Post subject: |
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| Cheers for posting this mate, good explanation of things. |
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sam
CaptiveBred Addict!
Joined: 10 Nov 2006
Posts: 711
Location: Glasgow, uk
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| Posted: Sat Aug 18, 2007 10:01 am Post subject: |
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Cheers for that Eggman-ive wondered about the genetics of the different morphs of ball python for a while now-nice to see its simple mendelians!
I find that punnet squares are a great way to "see" what you will get out of a cross... ie you write down the geneotype of the mother along one side, the father along the other side and just add up the genes...
Its useful to know that each gene has two "alleles" (basically two copies or versions....one form each parent) These are normally given as two letters in a row: ie Aa
Most normal types are "homozygous dominant" (having two of the same dominant allele, like AA for example)
Some morphs are recessive which means that if you only have one copy of the recessive gene then the animal will still look "normal". Having one copy of the recessive gene and one of the dominant is called being "heterozygous" (hence "hets") these will have the genotype Aa and will look the same as "homozygous dominant" animals
Having two copies of the reccessive gene makes the animal Homozygous recessive (homozygous-same alleles, reccesive-both are the recessive allele) These will have the aa genotype and will look different | Eggman wrote: | | albino, axanthic, clown, piebald, ghost, etc |
So crossing a visually albino (homozygous recessive) with a known heterozygous albino would result in the following cross:
____ a a
A __ Aa Aa
a___ aa aa
From this we see that half the offspring would be albino (homozygous recessive) and half would be "het albino" (heterozygotes carrying the albino recessive gene)
Incomplete dominance occurs when being heterozygous still causes a change in appearance (appearance is also known as "phenotype")
So for example if the Mojave gene was MM for a super mojave, Mm for a mojave and mm for a normal, if you crossed a normal to a mojave youd get the following square:
_____ m m
M___ Mm Mm
m___ mm mm
Sorry to kinda repeat what you said Eggman, but I just wanted to show an "alternative" way of figuring it out, as genetics can be tricky to pick up. 
with regards to the double cross, i think its slightly more complex than you said... though i assume you were "dumming it down" to make it easier to understand (as when you start bringing heterozygous Aa homozygous recessive bb cross Homozygous recessive aa heterozygous Bb you start to lose people!)
Anyway, sorry for the ramble guys, but as you may be able to tell I like my genetics 
Out of interest, Eggman, are there any sex linked colour morphs, or colour morphs relying on the additive effects of genes causing a colouration if the sum of the genes reaches a certain point? Are there any colourations whihc rely on X chromosome inactivation or Y inheritance?
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slippery42
CaptiveBred Addict!
Joined: 04 Aug 2006
Posts: 770
Location: north yorkshire
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| Posted: Sat Aug 18, 2007 10:05 am Post subject: genetics |
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Very good post Eggman!!!
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sam
CaptiveBred Addict!
Joined: 10 Nov 2006
Posts: 711
Location: Glasgow, uk
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| Posted: Sat Aug 18, 2007 12:25 pm Post subject: |
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hehe-believe me that one was just the basics  
The platinum ones very interesting... are you working with these yourself?
In snakes, the sex chromosomes are ZZ for male and ZW for females (ie the females are the heterozygous) so any sex linked colourations would appear mainly in males, but also in some females (but never passed from other to daughter)
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sam
CaptiveBred Addict!
Joined: 10 Nov 2006
Posts: 711
Location: Glasgow, uk
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| Posted: Sat Aug 18, 2007 12:41 pm Post subject: |
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hehe here sam shows his lack of knowledge regarding Royal morphs!
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