Q. What are introns, and how do they affect the processing of genetic information?
Introns, a feature of eukaryotic DNA, are intervening stretches of DNA lying between the exons. Exons represent message material which actually gets translated into protein, whereas the introns should eventually be excised fromthe final mRNA product. Initially, both exons and introns are coded into an mRNA transcript. Existence of introns and exons was demonstrated when it was discovered that only about one-third of the primary transcript of DNA was used to make protein. In a highly complicated process, intron regions are removed from rough primary transcript on DNA template to produce a secondary, mature mRNA that codes onlyfor the exons. It is now clear that terminator and initiator signals should mark thebeginning and end of each intron within a gene.
Despite the fact that intron isn't directly involved in shaping the final protein product, it appears to be essential to synthesis of a functional mRNA. Process of excising the intron regions involves the participation of RNA as an enzyme. This catalytic RNA is part of a protein-RNA particle termed as small nuclear ribonucleoprotein particle.