Why the reference is made with respect to the polarity of coding strand of structural gene?
Answers
Answer:
The promoter and terminator flank the structural gene in a transcription unit. The promoter is said to be located towards 5'-end (upstream) of the structural gene (the reference is made with respect to the polarity of coding strand).
It is a DNA sequence that provides binding site for RNA polymerase, and it is the presence of a promoter in a transcription unit that also defines the template and coding strands. By switching its position with terminator, the definition of coding and template strands could be reversed. The terminator is located towards 3'-end (downstream) of the coding strand and it usually defines the end of the process of transcription .
There are additional regulatory sequences that may be present further upstream or downstream to the promoter. Some of the properties of these sequences shall be discussed while dealing with regulation of gene expression.