In the lac operon, if lactose is present, which of the following occurs?
A. Lactose bind to RNA polymerase, which then binds to the promoter and transcribes the needed genes.
B. Lactose binds to the repressor, changing its shape so that it does not bind to the operator. RNA polymerase then transcribes the needed genes.
C. Lactose binds to the operon, which attracts RNA polymerase, then transcription of the needed genes occurs.
D. Lactose binds to the repressor, changing its shape so that it can bind to the operator and the structural genes are not expressed.
Answer: B
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