Differences and differences

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pedro21101
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Differences and differences

Post by pedro21101 » Sat Dec 17, 2005 8:45 am

Hello friends
I would be very happy to summarize all the differences between procaryotic and eucaryotic transcription and translation(and related things). For example like procaryotic mRNA is polycistronic, eucaryotic is monocistronic or eucaryotic mRNA must be processed - introns must go away and exons are spliced, cap must be added on 5 end and polyAAA on 3 end, or polycistronic mRNA of procaryotes is translated even when transcription havent stop yet and so on. It would be great if anyone who have some piece of knowledge about it would add it there.
Thanks thanks thanks

sdekivit
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Post by sdekivit » Sat Dec 17, 2005 8:31 pm

the 'cap' in prokaryotic mRNA is formylmethionine. And the ribosome subunits are different and eukaryotes have enhancer sequences.

Furthermore: eukaryotes have to build a whole basic transcription complex, while prokaryotes use a sigmafactor.

pedro21101
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Post by pedro21101 » Tue Dec 20, 2005 5:03 pm

Hm, by formylmethionin you probably mean initiatory aminoacid in formation of polypeptid chain cause cap means 7 methyl-GpppNpNpN....on the 5' end of mRNA. :wink:
One thing need i know. Are in eucaryotes represors as in procaroytes? if yes, how they can interact with operator when the whole DNA is already in interaction with histones? :?:
Thanks

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Post by sdekivit » Tue Dec 20, 2005 6:02 pm

yes there are repressors and enhancers in eukaryotes and are actively regulated.

--> there are several histon acetylases/deacetylases and histon remodelling complexes that can free the DNA from the histons such the there will get DNA-bindingsites available for proteins.

other histonmodifications are ubiquitylation and methylation for example. The combination of such modification determine the activity of transcritpion of the DNA. This is also known as the histoncode.

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Post by pedro21101 » Wed Dec 21, 2005 10:58 pm

Ive tried to search the web and i found pretty good page on this http://en.wikipedia.org/wiki/RNA_polyme ... _structure
and also there is written "Please note that this refers to various stages of the process as regulatory steps. It has not been proven that they are used for regualtion, but is very likely they are".

So is it already proven how is regulated transcription(means expression) in eucaryotes? For example how is preventing synthesis of lactase when i eat no lactose. I know we know how it is regulated in procaryotes but do we exactly know how it is regulated in eucaryotes(cause there are that histones)?
Thanks for patience :D

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