Question

Which one of the following is not a part of lac operon?

• A. Promoter
• B. Regulator
• C. Inducer
• D. Operator

Hint:

Distinguish between gene components (promoter, operator, structural genes) and regulatory molecules (repressor protein, inducer). An operon refers specifically to the set of genes transcribed together.

Answer 1

The Correct Option is C

The lac operon consists of several components on the DNA: a promoter (where RNA polymerase binds), an operator (where the repressor protein binds), and three structural genes (lacZ, lacY, lacA). The regulator gene (lacI) codes for the repressor protein but is typically located upstream and is not considered part of the operon itself. The inducer (allolactose) is a molecule that binds to the repressor protein, inactivating it. It is a signaling molecule, not a physical part of the operon's DNA sequence.