Question

Select the correct statement regarding post-transcriptional modification.

• A. In capping, methyl guanosine triphosphate is added at the 3' end.
• B. In tailing, adenylate residues (200-300) are added at 3'-end in a template-dependent manner.
• C. It is a process of conversion of mRNA to hnRNA.
• D. It involves removal of introns and joining of exons.

Answer 1

Answer: (D)

The primary transcripts of eukaryotes (hnRNA) contain both the exons and the introns and are non-functional. Hence, it is subjected to a process called splicing where the introns are removed and exons are joined in a defined order. hnRNA undergoes additional processing called as capping and tailing. In capping an unusual nucleotide (methyl guanosine triphosphate) is added to the 5'-end of hnRNA. In tailing, adenylate residues (200-300) are added at 3'-end in a template-independent manner. It is the fully processed hnRNA, now called mRNA, that is transported out of the nucleus for translation.