There is a mutation that is found in E. coli in the repressor that results in a molecule known as a super-repressor because it represses the lac operon permanently. Which of the following characteristics would you expect to observe in such a mutant?
A) It cannot bind to the operator.
B) It cannot make a functional repressor.
C) It cannot bind to the inducer.
D) It makes a repressor that binds CAP.

Question

Quizplus · Accepted Answer

The mutated repressor molecule is known as a "super-repressor" because it permanently represses the lac operon, meaning it will always be bound to the operator region, preventing transcription of the genes of the lac operon. This means that the mutated repressor cannot release from the operator, even in the presence of the inducer (such as lactose), which would normally result in the repressor dissociating from the operator, allowing transcription to occur. Therefore, the answer is C, as the super-repressor cannot bind to the inducer.

There Is a Mutation That Is Found in E