The precursor of mRNA i.e. hnRNA contains both introns and exons. Introns are removed and exons are joined by a process called splicing. The remaining mRNA is processed in two ways :
(i) Capping : Here, an unusual nucleotide called methyl guanosine triphosphate (cap) is added to the 5' end of hnRNA.
(ii) Tailing : Here, adenylate residues (200-300) are added at 3' end of hnRNA in a template independent manner.
When hnRNA is fully processed, it is known as mRNA, which is transported out of the nucleus to get translated.
