Question

The process of copying the genetic information from one strand of DNA into RNA is termed as transcription. The principle of complementarity of bases governs the process of transcription, also except that uracil comes in place of thymine.
Study the complete transcription unit given below and answer the following questions: 

(a) Name the main enzyme involved in the process of transcription. 
(b) Identify coding strand and template strand of DNA in the transcription unit. 
Attempt either sub-part (c) or (d): 
(c) Identify (C) and (D) in the diagram, mention their significance in the process of transcription. 
OR 
(d) Describe the location of (C) and (D) in the transcription unit.} 
 

Hint:

In transcription, the promoter (C) and terminator (D) are critical regulatory regions that control where RNA polymerase starts and stops synthesizing RNA.

Answer 1

Step 1: For (a), the main enzyme involved in transcription is RNA polymerase, which synthesizes RNA by reading the DNA template strand and adding complementary RNA nucleotides.
Step 2: For (b), in the transcription unit, the strand with 5’ to 3’ direction (bottom strand, B) is the coding strand, as it has the same sequence as the RNA (except T is replaced by U). The strand with 3’ to 5’ direction (top strand, A) is the template strand, as RNA polymerase reads it to synthesize RNA in the 5’ to 3’ direction.
Sub-part (c):
Step 3: For (c), (C) is the promoter region, where RNA polymerase binds to initiate transcription, and (D) is the terminator region, where transcription stops, signaling RNA polymerase to release the RNA and DNA. Their significance lies in defining the start and end of the transcription process.
Sub-part (d):
Step 4: For (d), (C) is located at the 5’ end of the coding strand (or start of the transcription unit), serving as the promoter, and (D) is at the 3’ end of the coding strand (or end of the transcription unit), acting as the terminator.
Thus, RNA polymerase drives transcription, the bottom strand (B) is coding and the top strand (A) is the template, with (C) and (D) as promoter and terminator, located at the start and end of the transcription unit, respectively.