Question

If an abnormal repressor protein could still bind allolactose but the binding of allolactose did not alter the conformation of the repressor protein, how would the expression of the lac operon be affected?

Answer 1

Without a conformational change in the lac repressor upon allolactose binding, the lac operon would remain repressed, preventing genes needed for lactose digestion from being transcribed, despite the presence of lactose.

Step-by-step explanation:

If an abnormal repressor protein could still bind allolactose but the binding did not alter the conformation of the repressor, the expression of the lac operon would likely be negatively affected. Normally, the binding of allolactose to the repressor induces a conformational change that prevents the repressor from binding to the operator sequence, thus de-repressing the operon and allowing RNA polymerase to transcribe the lac genes. However, without this conformational change, the repressor would remain bound to the operator, blocking RNA polymerase and preventing the transcription and expression of genes needed for lactose digestion. Essentially, the lac operon would be in a constantly repressed state in the presence of lactose, as the usual inducer, allolactose, fails to deactivate the repressor properly.