During transcription process in eukaryotes, 'capping' involves:

The correct answer is Option (2) → Addition of methyl guanosine triphosphate to 5' - end of hnRNA.

Option (1) Removal of methyl guanosine triphosphate from 5'- end of hnRNA. — Incorrect. In capping, methyl guanosine triphosphate is added to the 5′ end, not removed. The hnRNA does not have this cap to begin with.

Option (2) Addition of methyl guanosine triphosphate to 5' - end of hnRNA. — Correct. Capping is an addition, and it happens at the 5′-end of hnRNA. The 3′-end receives the poly-A tail instead (tailing).

Option (3) Addition of methyl guanosine triphosphate to 3'- end of hnRNA. — Incorrect. The cap goes on the 5′ end. At the 3′ end, tailing adds 200-300 adenylate residues (the poly-A tail).

Option (4) Removal of methyl guanosine triphosphate from 3'- end of hnRNA. — Incorrect. Capping adds the unusual nucleotide at the 5′ end; nothing is removed, and nothing happens to the 3′ end in this step.

NCERT Extract:
Types of RNA and the Process of Transcription – “… (ii) The second complexity is that the primary transcripts 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.”