I am a biochem student and this has almost made me pull my hair out, here is the image of the question I got wrong, and I am not sure if the question is wrong or I am, I think the operator is downstream of the promoter in the sense/coding strand, right?
Where do you expect to find the lac operator in an expression vector for the E. coli system?
A: 3' (downstream) of the promoter region
B: 5' (upstream) of the promoter region
I chose A, but the "correct" answer is B, why? Does this differ from plasmid to plasmid? We study plasmids such as the pET-(24)+. Note that I am assuming they are talking about the sense/coding strand and not the template.