If an operon is regulated by ____ control, genes are ____ by a regulatory protein called a ____
a. positive; on unless they are switched off; repressor
b. negative; off unless they are switched on; repressor
c. negative; on unless they are switched off; repressor
d. positive; off unless they are switched on; repressor
e. positive; on unless they are switched off; activator
ANSWER: c
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