Question #91efd
1 Answer
For reasons of efficiency I would think...
Explanation:
If there is need for production of an enzyme in the cell for instance, it is disadvantageous (read: madness!) for the whole chromosome to be transcribed: only the (coding part of) the gene itself is needed.
It would be the equivalent of taking your whole library outside, if you only want to read one specific, preselected book on the patio in the garden.
Apart from the organisational chaos it would produce (e.g. shortage of precursors if nothing else), it could/would also have disastrous effects: genes that should be kept "shut" might inadvertently be translated..
Only transcribing the code for the gene that is needed is not only more energy-efffective, it is a supreme way of gene expression control.....
Therefore, the resulting mRNA is MUCH shorter...
But since you mention "Primary Transcript", I assume you are referring to the processing, prior to translation into Protein.
This processing from pre-mRNA (precursor messenger RNA) to mature mRNA usually involves extraction of Introns , non-coding sequences that intersperse the Exons (coding regions), thereby shortening the original strand....
