Match List-I with List-II.

The lac operon consists of one regulatory gene (the $i$ gene – here the term $i$ does not refer to inducer, rather it is derived from the word inhibitor) and three structural genes ($z$, $y$ and $a$). The $i$ gene codes for the repressor of the lac operon. The $z$ gene codes for beta-galactosidase ($\beta$-gal), which is primarily responsible for the hydrolysis of the disaccharide lactose into its monomeric units, galactose and glucose. The $y$ gene codes for permease, which increases permeability of the cell to $\beta$-galactosides. The $a$ gene encodes a transacetylase.