lac operon: synthesizes proteins for the metabolism of lactose (lac genes)
• when lactose and glucose are present, lac genes are not expressed
• when only lactose is present, lac genes are expressed
What happens to the expression of the lacI gene if lactose is not available in the cell?
a) The lacI gene turns off.
b) The lacI gene increases its rate of transcription.
c) The lacI gene turns on.
d) There is no change—the lacI gene is constitutively expressed.