The $lac$ operon is a part of which of the following?

The structural unit of a gene is .....

Transposons can be used in which of the following processes?

In the Operon concept,the regulator gene functions as:

Assertion $(A):$ Regulation of $lac$ operon by repressor is referred to as negative regulation.
Reason $(R):$ Repressor protein binds to the operator region and prevents $\text{RNA}$ polymerase from transcribing the operon.

What effect would you expect if gene expression of the $lac$ operon were completely repressed?