There are three structural genes (x, y, a) which transcribe a polycistronic mRNA.
1. Gene z codes β-galactosidase (β-gal), which catalyses the hydrolysis of lactose into galactose and glucose.
2. Gene y codes for permease, which increases the permeability of the cell to β-galactosidase (lactose).
3. Gene a codes for transacetylase, which catalyses the transacetylation of lactose into its active form.
