Question

How are lac operons regulated?

Answer 1

Tight regulation. Normally, the lac operon is turned off. A repressor protein binds the operator (control) region upstream of the operonpreventing transcription. When lactose is present outside the cell, it crosses the cell membrane and acts as an inducer of the operon.

Answer 2

ANSWER

The lac operon. In the absence of lactose, the repressor protein encoded by the I gene binds to the lac operator and prevents transcription. Binding of allolactose to the repressor causes it to leave the operator. This enables RNA polymerase to transcribe the three genes of the operon.

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