Question

Select the correct statements regarding the process of transcription in eukaryotes.
(i) The strand of $dsDNA$ which takes part in transcription process is called as coding strand.
(ii) The enzyme $RNA$ polymerase can catalyse polymerisation only in one direction i.e., $5' \rightarrow 3'$.
(iii) An unusual nucleotide methyl guanosine triphosphate is added to the $5'$ end of $hnRNA$ during capping.
(iv) During tailing process, adenylate residues $(200 - 300)$ are added at $3'$ end in a template independent manner.

• A. (i) and (ii)
• B. (iii) and (iv)
• C. (ii), (iii) and (iv)
• D. (i), (ii), (iii) and (iv)

Answer 1

Answer: (C)

The primary $mRNA$ transcript is longer and localised into the nucleus, where it is also called heterogenous nuclear $RNA (hnRNA) $or pre-$mRNA$. At the $5'$ end of $hnRNA$, a cap (consisting of $7$-methyl guanosine triphosphate or $7 mG$) and a tail of poly $A$ (Adenylate residues) at the $3'$ end are . added. These processes are respectively called as capping and tailing. The cap is a chemically modified molecule of guanosine triphosphate $(GTP)$. The primary $mRNAs$ are made up of two types of segments; non-coding introns and the coding exons. The introns are removed by a process called $RNA$ splicing and the exons are joined in a defined order.