Lac operon codes for lactose degrading enzymes in bacteria. Lac operon consists of three structural genes which are as follows:
1) lac z gene: This gene codes for enzyme b-galactosidase. This enzyme breakdown lactose to glucose and galactose. It also isomerizes lactose to allolactose.
2) lac y gene: This gene codes for enzyme Permease which helps in transport of lactose into cell.
3) lac a gene: This gene codes for enzyme Transacetylase