Solutions For An Introduction to Genetic Analysis Chapter 11 Problem 4P

The lac operon contains two types of genes: structural genes and regulatory genes. There are three structural genes present in the lac operon, they are lac z, lac y, and lac a. There are two regulatory genes present in lac operon: the operator and the promoter, which control the transcription of the structural genes.

The repressor protein synthesized by gene i binds specifically to the overlapping sequence in the operator to inhibit transcription. If the bacterium is living in the medium containing lactose, then lactose binds to the repressor and makes it unfit for binding. So, RNA polymerase can transcribe the structural genes.