Question

How are structural genes activated in the lac operon in E.coli? [3]

Answer 1

In lac operon of E.coli, the repressor is synthesised constitutively from the i gene which binds to the operator region of the operon and prevents RNA polymerase from transcribing the structural genes. In the presence of an inducer (lactose or allolactose), the repressor is inactivated by interaction with the inducer. This allows RNA polymerase access to the promoter and transcription of the structural genes proceeds. Therefore addition of an inducer can activate the structural genes of the lac operon. [3]