Transcription unit is represented in the diagram given below.

Identify site (i), factor (ii) and Enzyme (iii) responsible for carrying out the process.

Options

A. (I) Promoter Site, (II) Rho factor (III) RNA polymerase
B. (I) Terminator Site, (II) Sigma factor (III) RNA polymerase
C. (I) Promoter Site, (II) Sigma factor (III) RNA polymerase
D. (I) Promoter Site, (II) Sigma factor (III) DNA polymerase

Answer

C

Explanation

A transcription unit consists of the following:
(1) Promoter: Promoter can be defined as a DNA sequence that serves as the binding site for RNA polymerase. It is located at the 5.-end (upstream) of the structural gene. The presence of promoter region also defines the template and coding strands.
By switching its position with terminator, the definition of coding and template strands could be reversed.
(2) Structural gene : The structural gene coding for a particular protein is flanked by the promoter and terminator.
(3) Terminator : Terminator is the region of the transcription unit that ends the process of transcription. It is located towards 3.- end (downstream) of the coding strand.

Schematic Structure of a Transcription Unit