Solution

In the lac operon, the y gene codes for permease. Permease increases the permeability of the cell to lactose, i.e. it transports lactose into the bacterial cell. ($\beta$-galactosidase hydrolyses lactose into glucose and galactose, and transacetylase is coded by the a gene.)

Concept Role of lac operon gene products in lactose uptake/metabolism

Molecular Basis of Inheritance in past papers

200 questions from this chapter have appeared across 27 exam years.