post transcriptional modification..

[km1865]

I always thought post transcriptional modification of mRNA strictly does not occur in prokaryotes.. since their mRNA is essentially ready for translation.. however, according to wiki "mRNA can also be polyadenylated in prokaryotic organisms, where poly(A) tails act to facilitate, rather than impede, exonucleolytic degradation" so obviously then the reasons for polyadenylation are different in prok vs eukaryotes.. so for the purposes of the MCAT prokaryotes DO NOT undergo posttranslational modification, right? (also does the polyadenylation of mrna in prokaryotes always occur? i would assume no since they use this funciton to destroy their mrna?)

ALSO, I got an AAMC question wrong which was basically asking how transcription/translation differs in pro vs eukaryotes and I selected eukaryotes destroy their mRNA as soon as it is formed, cuz i thought they were talking about destroying the introns not the whole strand.. just to clarify NONE of this occurs in prokaryotes right? on a side note, IS the mRNA destroyed by BOTH prokaryotes and eukaryotes as soon as it is formed (w/o the post-modifications, aka is it equally unstable for both pro and eu?)

Thanks for the help!

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[Phlame217]

You should really go back and get the fundamentals of eukaryotic and prokaryotic protein production down.

The basics:

Prokaryotes: Essentially the mRNA is made (translated) and transcribed within the same transcriptional/translational complex. The mRNA is bound to ribosomes as it is produced and the protein is made in the same area as the mRNA is translated. The mRNA is then rapidly degraded after protein production. NO post transcriptional modification is done. This is qualified by the fact to no splicing occurs. No introns, no exons, etc. The whole polyadenylated thing isn't really post transcriptional as it occurs as transcription is finishing.

Eukaryotes: Things are compartmentalized and do not occur all in the same area. mRNA is translated within the nucleus. Before exiting, intron/exon splicing occurs (the definition of post transcriptional modification). The mRNA exits and then is bound and translation occurs.

 

[Bumbl3b33]

I always thought post transcriptional modification of mRNA strictly does not occur in prokaryotes.. since their mRNA is essentially ready for translation.. however, according to wiki "mRNA can also be polyadenylated in prokaryotic organisms, where poly(A) tails act to facilitate, rather than impede, exonucleolytic degradation" so obviously then the reasons for polyadenylation are different in prok vs eukaryotes.. so for the purposes of the MCAT prokaryotes DO NOT undergo posttranslational modification, right? Yup. (also does the polyadenylation of mrna in prokaryotes always occur? i would assume no since they use this funciton to destroy their mrna? Prokaryotes don't use the cap or a-tail; all of this happens in golgi, which they don't have. MCAT=general; Wiki= detailed, yeah some do actually make mRNA modifcations, but not a majority.)

ALSO, I got an AAMC question wrong which was basically asking how transcription/translation differs in pro vs eukaryotes and I selected eukaryotes destroy their mRNA as soon as it is formed, cuz i thought they were talking about destroying the introns not the whole strand.. just to clarify NONE of this occurs in prokaryotes right? This = alternative splicing? To my knowledge, no, it's exclusive to eurkaryotes, if someone else knows else wise for the MCAT, please feel free to correct meon a side note, IS the mRNA destroyed by BOTH prokaryotes and eukaryotes as soon as it is formed (w/o the post-modifications, aka is it equally unstable for both pro and eu?) mRNA would be 'destroyed' after it has been transcribed.

 

[km1865]

thanks. Here's a handout I found thats really useful
http://dspace.mit.edu/bitstream/han...C811-4E1C-AEC4-CC3E0C95AB88/0/Prok_vs_Euk.pdf