Statement I: The regulatory gene in the lac operon is the "i" gene, which codes for the inducer of the operon.
Statement II: The z gene in the lac operon codes for beta-galactosidase, which hydrolyses lactose into galactose and glucose.
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Only statement II is correct.
Statement I — False. The regulatory gene of the lac operon is the i gene, but it codes for the repressor, not the inducer. The letter i comes from ‘inhibitor’. The inducer is lactose (or allolactose), which comes from outside and is not coded by any gene of the operon.
Statement II — True. The z gene codes for beta-galactosidase. This enzyme breaks the disaccharide lactose into its two monomers, galactose and glucose.
NCERT Extract:
The Lac Operon – “… 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 (β-gal), which is primarily responsible for the hydrolysis of the disaccharide, lactose into its monomeric units, galactose and glucose.”