Question

Which mutation is expected to have a similar effect to a mutation in which the LacI repressor is no longer able to bind to the operator?

A) Mutation in the promoter region
B) Mutation in the coding sequence of the structural gene
C) Mutation in the inducer-binding site of the repressor
D) Mutation in the Shine-Dalgarno sequence

Answer 1

A mutation in the inducer-binding site of the LacI repressor would have a similar effect to a mutation preventing the repressor from binding to the operator, leading to continuous expression of the lac operon.

Step-by-step explanation:

The mutation expected to have a similar effect to a mutation in which the LacI repressor is no longer able to bind to the operator is a mutation in the inducer-binding site of the repressor. Both of these mutations would result in the lac operon being expressed continuously because nothing is preventing transcription. A mutation in the inducer-binding site would prevent allolactose (the inducer) from binding to the repressor and causing it to release from the operator, which would have a similar outcome to the repressor not being able to bind to the operator in the first place.. If there is a mutation in the promoter sequence, RNA polymerase may not be able to attach properly, resulting in decreased or no transcription of the lac operon.