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  b-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.