exons and introns...?

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bass_lasso9
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exons and introns...?

Post by bass_lasso9 » Tue Nov 01, 2005 1:39 pm

hi all...
i wanna ask about exons and introns...
I don't know what exons and introns segments mean?
in what part of DNA-template...? or in m-RNA..?
and what happen with them in protein synthesis process...?

and what about mitochondrial DNA...?
how do they produce their own protein? with protein synthesis or what?

and about m-RNA encode..
i've read in one of my biology book it says that stop sequence or stop signal in m-RNA encoding is in UAA, UAG, and UGA codon.. but in another book it says that is in AAA codon that called poly A tail...
that's confuse me.. could you please tell me which one is correct..?

thank's for your help... :roll:

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Morris
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Post by Morris » Tue Nov 01, 2005 4:53 pm

Gene is composed by exons and interons: in the transcription both become mRNA: but mRNA with both isn't translated, and is called immature mRNA (if I'm wrong correct me :lol: :lol: ); the mRNA become ready for translating when introns are rimoved from it in a process called "splicing"; In protein synthesis are translated only exons.
Mitochondrial DNA produces protein by protein synthesis only for the mitochondrion, not for whole organism: for it is used the encoding DNA of the nucleus.
I rimember that protein synthesis stops with a stop codon; poly-A in my opinion it's a recognition site for ribosome; because I think how can ribosome recognize that there is a mRNA that must be traslated; I think with poly-A tail. :wink: :wink:

sdekivit
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Post by sdekivit » Tue Nov 01, 2005 5:54 pm

poly-A-tail is not encoded in the DNA --> it's a post translational modification.

rabidrhymer
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Post by rabidrhymer » Wed Nov 02, 2005 7:48 am

but what are exons and introns???
'The Rabidrhymer strikes again'

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Morris
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Post by Morris » Wed Nov 02, 2005 5:29 pm

Exons are the encoding part of the immature mRNA, introns don't encode for AA and for it they must be removed.

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