Question

Consider the following statements
1. The promoter is located towards the 5’ end of the structural gene with respect to the template strand.
2. The promoter is located towards the 3’ end of the structural gene with respect to the template strand.
3. The terminator is located towards the 3’ end of the structural gene with respect to the template strand.
4. The terminator is located towards the 5’ end of the structural gene with respect to the template strand.

The correct statements are:

• A. 1 and 2
• B. 2 and 3
• C. 3 and 4
• D. 2 and 4

Answer 1

The correct option is D 2 and 4

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 is also referred to as a template strand. The template strand of DNA serves in mRNA synthesis while the other strand that has the polarity 5'→3' is called a coding strand.

In a transcription unit, the structural gene is flanked by promoter and terminator regions.

Promoter region is responsible for initiation of transcription. The enzyme, RNA polymerase binds to this DNA sequence and initiates transcription.

The promoter is present towards the 5’ end of the structural gene with respect to the coding strand.
However, when considering the template strand, it is present towards the 3’ end.

Terminator region is responsible for the termination of the process of transcription.

Similarly, the terminator is present towards the 3’ end of the structural gene with respect to the coding strand. However, when considering the template strand (acts as a template for the synthesis of RNA), it is present towards the 5’ end.