Question

In the lac- operon model, lactose molecules function as

• A. inducers, which bind with the operator gene
• B. repressors, which bind with the operator gene
• C. inducers which bind with the repressor protein
• D. corepressors which bind with repressor protein

Answer 1

Answer: (C)

In bacteria, regulated genes are often clustered into units called operon, consisting of a single promoter, operator and structural genes. In Lac- operon, represser protein binds to the operator and blocks attachment of RNA polymerase to the promote and operon is switched off. In an inducible operon, binding of an inducer (lactose in case of Lac-operon) to the active represser prevents its attachment to operator thereby turning on structural gene.