12-28-2011, 03:13 PM
21.The lac operon is expressed when
A) glucose is high and lactose is present.
B) glucose is high and lactose is absent.
C) glucose is low and lactose is present.
D) glucose is low and lactose is absent.
E) glucose is low, regardless of the presence or absence of lactose.
22.When in a complex with ________, the CAP protein binds to the CAP site and ________ the expression of the lac operon.
A) glucose ; switches on
B) glucose ; switches off
C) lactose ; switches on
D) cAMP ; switches on
E) cAMP ; switches off
23.In the absence of lactose, the lac repressor is
A) active and can bind to the operator.
B) active and cannot bind to the operator.
C) inactive and cannot bind to the promoter.
D) inactive and can bind to the operator.
E) inactive and cannot bind to the operator.
A) glucose is high and lactose is present.
B) glucose is high and lactose is absent.
C) glucose is low and lactose is present.
D) glucose is low and lactose is absent.
E) glucose is low, regardless of the presence or absence of lactose.
22.When in a complex with ________, the CAP protein binds to the CAP site and ________ the expression of the lac operon.
A) glucose ; switches on
B) glucose ; switches off
C) lactose ; switches on
D) cAMP ; switches on
E) cAMP ; switches off
23.In the absence of lactose, the lac repressor is
A) active and can bind to the operator.
B) active and cannot bind to the operator.
C) inactive and cannot bind to the promoter.
D) inactive and can bind to the operator.
E) inactive and cannot bind to the operator.
