Transcription involves transfer of genetic information from DNA to functional mRNA. In eukaryotes, the modification of newly formed primary mRNA transcripts (pre-mRNA) to produce functional $m$ RNA is called RNA processing or post transcriptional modification. It occurs in the nucleus and involves gene splicing (ie, removal of introns from primary transcript and splicing together of exons) and capping. Capping involves formation of a cap at $5^{\prime}$ end by condensation of guanylate residues. The fully processed mRNA molecule is exported from the nucleus to the ribosomes for translation in the cytoplasm.