Question

Match the following regarding transcription:

p	Initiation	i	Ribonucleotides are polymerised according to the code
q	Elongation	ii	RNA polymerase binds to promoter
r	Termination	iii	mRNA is bound by protective molecules
s	Capping	iv	RNA polymerase detaches from DNA

• A. p-i, q-ii, r-iii, s-iv
• B. p-ii, q-iii, r-iv, s-i
• C. p-ii, q-i, r-iv, s-iii
• D. p-iv, q-iii, r-ii, s-i

Answer 1

The correct option is C p-ii, q-i, r-iv, s-iii

The synthesis of RNA from a DNA strand is called transcription.

A transcription unit in DNA consists of three regions: promoter, structural gene and terminator.

In the transcription unit, the strand that has the polarity 3'→5' acts as a template, and serves in mRNA synthesis while the other strand that has the polarity 5'→3' is called a coding strand.

Transcription takes place in three major steps- initiation, elongation and termination.

For initiation of transcription, the sigma factor of RNA polymerase is required and for termination the rho factor encounters RNA polymerase.

Initiation involves binding of RNA polymerase to the promoter. The promoter region is the sequence that initiates or starts the process of transcription.

This is followed by polymerisation of ribonucleotides according to the template (elongation).

The last step is termination, during which RNA polymerase detaches from the DNA in order to end the transcription process.

In eukaryotes, the newly formed pre-mRNA or primary transcript then undergoes processing. It involves addition of methyl guanosine triphosphate at the 5’ end i.e., capping, and addition of adenylate residues at the 3’ end of the primary transcript i.e., tailing. Both these processes protect the mRNA from the action of unwanted enzymes.