Which one of the following regions is not present in transcriptional…

The correct answer is Option (3) → Initiation factor

Option (1) A Promoter — A region of the transcription unit. The promoter lies upstream of the structural gene, towards the 5′-end of the coding strand. It gives the binding site for RNA polymerase, and its position decides which strand is the template and which is the coding strand.

Option (2) The Structural gene — A region of the transcription unit. It is the stretch between the promoter and the terminator. This is the part that is copied into RNA.

Option (3) Initiation factor — Not a region of the transcription unit. An initiation factor is a protein, not a stretch of DNA. In bacteria the sigma factor (σ) joins RNA polymerase so that it can start transcription at the promoter. It helps transcription begin, but it is not part of the DNA unit.

Option (4) A Terminator — A region of the transcription unit. The terminator lies downstream of the structural gene, towards the 3′-end of the coding strand. It marks the point where transcription stops.

Note: The same question was also asked in CUET (UG) 2025 on 29-05-2025 (Slot 1).

NCERT Extract:
Transcription Unit –
Types of RNA and the Process of Transcription – “… The RNA polymerase is only capable of catalysing the process of elongation. It associates transiently with initiation-factor (σ) and termination-factor (ρ) to initiate and terminate the transcription, respectively.”