a. There are three structural genes which transcibe a polycistronic mRNA.
1. Gene z codes b-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 lactose.
3. Gene a codes for transacetylase, which catalyses the transacetylation of lactose into its active form.
b. RNA polymerase triggers the transcription of these genes.