preQ: Under which conditions will E. coli
cells express (transcribe and translate) lots of
beta-galactosidase?
A)
B)
C)
D)
E)
In medium with glucose as the only sugar
In medium with glucose and lactose
In medium with lactose as the only sugar
In medium with galactose
All of the above
preQ: If the repressor gene is mutated, so that
no repressor protein is made, then
a) The lac operon will never be induced
b) The lac operon will always be induced
c) The lac operon will be induced whenever
lactose is present
d) The lac operon will be induced whenever
glucose is absent
e) The lac operon will be induced only when
both lactose and glucose are present
preQ: What causes induction of the lac
operon?
A) When repressor binds to the operator,
regardless of CAP
B) When CAP binds to the promoter,
regardless of Repressor
C) When Repressor binds to inducer
D) When both A) and B) occur
E) When CAP binds to the promoter and
Repressor is not bound to the operator
preQ: In wild-type E. coli cells in medium
with glucose, and no lactose:
A. CAP binds to promoter
B. Repressor binds to operator
C. Both CAP and Repressor bind to promoter and
operator, respectively
D. Neither bind
preQ: If a mutation eliminates binding of inducer
to the repressor, but the repressor still binds to
DNA;
A) The lac operon will be always induced
B) The lac operon will never be induced
C) The lac operon will be induced whenever
glucose is absent, regardless of the presence or
absence of lactose
D) The lac operon will be induced only when both
glucose and lactose are present
E) The lac operon will be induced only when
glucose is present and lactose is absent
Lac operon demonstration
• Need volunteers for
– RNA polymerase
– Repressor protein
– CAP protein
postQ: Under which conditions will E. coli
cells express (transcribe and translate) lots of
beta-galactosidase?
A)
B)
C)
D)
E)
In medium with glucose as the only sugar
In medium with glucose and lactose
In medium with lactose as the only sugar
In medium with galactose
All of the above
postQ: If the repressor gene is mutated, so that
no repressor protein is made, then
a) The lac operon will never be induced
b) The lac operon will always be induced
c) The lac operon will be induced whenever
lactose is present
d) The lac operon will be induced whenever
glucose is absent
e) The lac operon will be induced only when
both lactose and glucose are present
postQ: What causes induction of the lac
operon?
A) When repressor binds to the operator,
regardless of CAP
B) When CAP binds to the promoter,
regardless of Repressor
C) When Repressor binds to inducer
D) When both A) and B) occur
E) When CAP binds to the promoter and
Repressor is not bound to the operator
postQ: In wild-type E. coli cells in medium
with glucose, and no lactose:
A. CAP binds to promoter
B. Repressor binds to operator
C. Both CAP and Repressor bind to promoter and
operator, respectively
D. Neither bind
postQ: If a mutation eliminates binding of inducer
to the repressor, but the repressor still binds to
DNA;
A) The lac operon will be always induced
B) The lac operon will never be induced
C) The lac operon will be induced whenever
glucose is absent, regardless of the presence or
absence of lactose
D) The lac operon will be induced only when both
glucose and lactose are present
E) The lac operon will be induced only when
glucose is present and lactose is absent