NEET Zoology Question (2026) — Solution

Step-by-step solution

The i gene in the lac operon codes for the repressor protein. It is a regulatory gene that is constitutively expressed, meaning it is transcribed continuously to maintain a basal level of repressor in the cell. Galactose does not act as an inducer of the lac operon; lactose or allolactose serves as the inducer. Lactose binds to the repressor protein and inactivates it, preventing it from binding to the operator region. Genes z, y, and a are structural genes that share a single common promoter, whereas the i gene has its own separate promoter. Answer: Gene i is constitutively expressed