Question

Which of the following steps in transcription is catalysed by $RNA$ polymerase?

• A. Initiation
• B. Elongation
• C. Termination
• D. All of the above

Answer 1

Answer: (D)

All of the above

Answer 2

There is single $DNA$-dependent $RNA$ polymerase that catalyses transcription of all types of $RNA$ in bacteria. $RNA$ polymerase binds to promoter and initiates transcription (Initiation). It uses nucleoside triphosphates as substrate and polymerises in a template dependent fashion following the rule of complementarity. It somehow also facilitates opening of the helix and continues elongation. Only a short stretch of $RNA$ remains bound to the enzyme. Once the polymerases reaches the terminator region, the nascent $RNA$ fall off, so also the $RNA$ polymerase. This results in termination of transcription. The $RNA$ polymerase is only capable to catalysing the process of elongation. It associates transiently with initiation-factor $(\sigma)$ and termination-factor$(\rho)$ to initiate and terminate the transcription respectively. Association with these factors alter the specificity of the $RNA$ polymerase to either initiate or terminate.