Question

The placement of the operator sequence between the promotor and the structural genes is critical to the proper function of the lac operon.

Which of the following mutations could lead to constitutive expression of the genes of the lac operon?A. A mutation in the lac-Z geneB. A super repressor mutationC. A mutation in the operator sequenceD. A mutation in the lac-Y gene

Answer 1

C. A mutation in the operator sequence

Step-by-step explanation:

The operator sequence of the lac operon serves as the site for the binding of repressor protein. When repressor protein is bound to the operator sequence, the enzyme RNA polymerase is inhibited to carry out the process of transcription of the structural genes of the operon. Binding of allolactose to repressor does not allow it to bind to the operator sequence. This allows the expression of the lac operon in the presence of lactose sugar.

Any mutation in the operator region that disturbs the binding of the repressor to it would allow the expression of lac operon even in the absence of lactose allowing it to be expressed in a constitutive manner.