Describe the three processes that commonly modify eukaryotic

Describe the three processes that commonly modify eukaryotic pre-mRNA.

Solution

three processes that modify eukaryotic pre mRNA are capping, tailing and splicing. these modifications are required for easy transport of messenger RNA from nucleus to cytoplasm, for stabilisation of RNA and for prevention of degradation of RNA molecules in cytoplasm where translation occurs.

5\' CAPPING: it involves addition of 7-methylGuanosine to the 5\' end. 5\' phosphate is removed by phosphohydrolase enzyme and modified GMP(containing methyl group at 7-N position, methyl is obtained from SAM) transferred to this 5\' end by Guanylyl transferase and capping is done.

3\' TAILING/POLYADENYLATION: it involves addition of poly A tail to 3\' end and is mediated by Poly A polymerase(PAP) which is a template independent polymerase and adds 20-200 Adenosne to 3\' end.

INTRON SPLICING: it is a process of removal of introns(non coding regions of DNA) and joing of exons(coding regions). Mediated via a protein machinery called spliceosome which splice out the junk.

5\' CAPPING	INTRON SPLICING	3\' POLYADENYLATION
involves methylation of guanines involves addition of guanosine monophosphates is done by guanylyl transferase.	involves removal of an intron involves the joining of adjacent exons is done by the spliceosome	begins with the cleavage of pre-mRNA downstream of the polyadenylation sequence. is done by polyadenylated polymerase results in the addition of 20 to 200 adenine nucleotides