Post-transcriptional changes : Modification at 5′ end of primary RNA (Heterogenous RNA or hnRNA) transcript is called capping. During capping, an extra guanosine residue in first added to the terminal nucleoside triphosphate of the primary RNA transcript. Guanosine residue is further modified by addition of methyl groups. Capping prevents the 5′ end of TORNA from being digested by exonucleases. It aids in the transport of m-RNA out of the nucleus and plays an important role in the m-RNA translation.
Addition of a string of adenosine residues, forming a poly (A) tail at 3′ end of the TO-RNA.
The process of removal of those parts of primary transcript, corresponding to introns and joining together of exons, is known as splicing.