Arrange the given structures in correct sequence of transcription unit when we move from left to right?
(A) Terminator
(B) Promoter
(C) Structural gene
(D) Transcription start site
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (B), (D), (C), (A)
A transcription unit is read on the coding strand from 5′ (left) to 3′ (right).
(B) Promoter — first. The promoter lies upstream, towards the 5′ end of the structural gene. RNA polymerase binds here.
(D) Transcription start site — second. The promoter is placed just before this site, where the first nucleotide of the RNA is copied.
(C) Structural gene — third. This is the region that is transcribed into RNA.
(A) Terminator — fourth. The terminator lies downstream, at the 3′ end, and marks where transcription stops.
NCERT Extract:
Transcription Unit – “A transcription unit in DNA is defined primarily by the three regions in the DNA :
(i) A Promoter
(ii) The Structural gene
(iii) A Terminator There is a convention in defining the two strands of the DNA in the structural gene of a transcription unit.”