Question

In a post-transcriptional modification called tailing, ____ residues are added at the ____ of mRNA.

• A. adenylate, 5'-end
• B. guanylate, 3'-end
• C. adenylate, 3'-end
• D. guanylate, 5'-end

Answer 1

The correct option is C adenylate, 3'-end

After transcription (RNA synthesis from a DNA sequence), the precursor of messenger RNA (mRNA) called heterogenous nuclear RNA (hnRNA) undergoes modifications. One such modification is called tailing. In tailing, adenylate residues $(200-300)$ are added at 3'-end without any requirement of template. After modification, this fully processed hnRNA is now termed mRNA. It is then transported out of the nucleus for translation (protein synthesis from mRNA).