Thread: mono vs polycistronic

why is that a eukaryotes mRNA transcript is so much larger than a bacterias but mostly translates only one polypeptide (monocistronic) while bactrial mRNA can be polycistronic? and what is the point of introns?

Procaryotes do not have excess DNA and this allows them to replicate more rapidly. Eucaryotes have these extra bits of DNA between exons, I believe, in order to allow discrete modules of information to be moved about the genome more easily. Eucaryotes do not need to replicate rapidly to compete with others in their niche.

Hi Dkav,

and what is the point of introns?

Introns allow more than one mRNA transcript to be produced from the same bit of DNA. As such, the presence of introns confers on an organism the ability to store more information in a given stretch of DNA, than would be possible for organisms lacking introns. I do not know whether or not the increased capacity to store information provided an evolutionary advantage to organisms containing introns - I would suspect so.

Here is a recent Nature Reviews Genetics article discussing the evolutionary sigificance of alternative splicing:

Hadas Keren, Galit Lev-Maor and Gil Ast (2010) Alternative splicing and evolution: diversification, exon definition and function. Nature Reviews Genetics 11, 345-355 (May 2010) doi:10.1038/nrg2776

If you are unable to access this Review but would like to read it please let me know and I will send it to you.

Tridimity