The structural genes of the lac operon are transcribed into a single mRNA,
which is then translated into the three enzymes.
The lacZ gene encodes β-galactosidase, an enzyme that digests the disaccharide lactose into glucose and galactose.
The lacY gene codes for the enzyme permease, a transport protein which facilitates the diffusion of lactose into the cell.
The lacA gene codes for the enzyme transacetylase.