Which of the following statements are correct with reference to a transcription unit ?

A. A transcription unit in DNA is defined primarily by three regions : promoter, structural gene and terminator.
B. The promoter is said to be located towards the 5’-end of the structural gene.
C. The promoter is a DNA sequence that provides binding site for RNA polymerase.
D. The promoter defines the template and coding strands.
E. The terminator is located towards the 3’-end of the coding strand and it defines the end of the process of transcription.

Choose the correct answer from the options given below :

The correct answer is: A, B, C, D and E.

Explanation of each statement:

Statement A: A transcription unit in DNA is defined by three regions – the promoter, the structural (coding) gene, and the terminator. The promoter initiates transcription, the structural gene contains the sequence that will be transcribed into RNA, and the terminator signals where transcription stops.

Statement B: The promoter is located upstream of the structural gene, which corresponds to the 5′‑end of the coding strand. This placement allows RNA polymerase to bind first and then move downstream toward the 3′‑end.

Statement C: The promoter is a DNA sequence that provides a binding site for RNA polymerase (and associated transcription factors). Without this site, the enzyme could not begin synthesis of the RNA transcript.

Statement D: The promoter defines which strand serves as the template strand and which serves as the coding (non‑template) strand. Its orientation fixes the direction of transcription, thereby designating the two strands.

Statement E: The terminator is located near the 3′‑end of the coding strand. When RNA polymerase reaches this region, the terminator causes the newly formed RNA transcript to be released, ending transcription.

All five statements accurately describe aspects of a transcription unit, so the correct choice includes A, B, C, D and E.