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The lac-operon consists of a regulatory gene (i), a promoter (p), an operator (o), and three structural genes (z, y, and a). The regulatory gene 'i' codes for the repressor protein.
The gene 'i' is responsible for producing the repressor protein. It is termed 'constitutive' because it is expressed continuously at a low level in the cell, regardless of the presence or absence of the inducer (lactose).
Option (A) is incorrect because allolactose (an isomer of lactose), not galactose, is the inducer. Option (C) is incorrect because lactose/allolactose inactivates the repressor by binding to it, preventing it from binding to the operator. Option (D) is incorrect because the 'i' gene has its own separate promoter and is not part of the polycistronic transcript of the structural genes.
Final Answer: B