BIO 170 Ch 18 Control of
Gene Expression in Bacteria
Comprehensive Questions
with Verified Answers
Graded A+
1. Repica plating is used to isolate mutants that Answer: cannot grow in a
particular condition
2. Why are the genes involved in lactose metabolism considered to
be an oper- on Answer: they all are controlled by the same promoter
3. In the lac operon, the repressor inhibits transcription when Answer:
the repressor is not bound to the inducer
4. Activators bind to regulatory sequences in Answer: DNA
5. Activators bind to polymerase Answer: RN
6. How does inducer exclusion control gene expression in the lac
operon? Answer: Inducer exclusion controls gene expression in the lac operon by preventing
the transport of lactose into the glycolytic pathway when glucose is present in order to only allow the
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, use of glucose.
7. A regulon is a set of genes controlled by a Answer: one type of regulat
of transcription.
8. Why does E. coli express genes for glycolytic enzymes constitutively?
Answer: It expresses them constitutively because they are genes that need to be expressed all
the time to produce ATP which is needed all the time so they constantly remain on
9. Explain the difference between positive and negative control over
transcrip- tion. Answer: The ditterence between positive and negative control over transcription
is that positive control promotes transcription and increases the frequency of initiation of transcription
while negative control of transcription prevents the initiation of transcription and acts a repressor
when glucose is present.
10. Predict what would happen if the lac repressor protein were
altered so it could not bind to the inducer. Answer: The repressor would
always be bound to DNA.
11. Predict what would happen to regulation of the lac operon if
the lacI gene were moved 50,000 nucleotides upstream of its normal
location. Answer: The location of the lacI gene doesn't matter so regulation would be
normal
12. If any of the following hypothetical drugs could be
developed, which would be most effective in preventing cholera?
a. a drug that increased the amount of the ToxR activator
b. a drug that blocked the DNA-binding activity of the activator
c. a drug that increased rates of transcription in V. cholerae
d. a drug that increased rates of translation in V.chloerae. Answer: a
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6
Gene Expression in Bacteria
Comprehensive Questions
with Verified Answers
Graded A+
1. Repica plating is used to isolate mutants that Answer: cannot grow in a
particular condition
2. Why are the genes involved in lactose metabolism considered to
be an oper- on Answer: they all are controlled by the same promoter
3. In the lac operon, the repressor inhibits transcription when Answer:
the repressor is not bound to the inducer
4. Activators bind to regulatory sequences in Answer: DNA
5. Activators bind to polymerase Answer: RN
6. How does inducer exclusion control gene expression in the lac
operon? Answer: Inducer exclusion controls gene expression in the lac operon by preventing
the transport of lactose into the glycolytic pathway when glucose is present in order to only allow the
1/
6
, use of glucose.
7. A regulon is a set of genes controlled by a Answer: one type of regulat
of transcription.
8. Why does E. coli express genes for glycolytic enzymes constitutively?
Answer: It expresses them constitutively because they are genes that need to be expressed all
the time to produce ATP which is needed all the time so they constantly remain on
9. Explain the difference between positive and negative control over
transcrip- tion. Answer: The ditterence between positive and negative control over transcription
is that positive control promotes transcription and increases the frequency of initiation of transcription
while negative control of transcription prevents the initiation of transcription and acts a repressor
when glucose is present.
10. Predict what would happen if the lac repressor protein were
altered so it could not bind to the inducer. Answer: The repressor would
always be bound to DNA.
11. Predict what would happen to regulation of the lac operon if
the lacI gene were moved 50,000 nucleotides upstream of its normal
location. Answer: The location of the lacI gene doesn't matter so regulation would be
normal
12. If any of the following hypothetical drugs could be
developed, which would be most effective in preventing cholera?
a. a drug that increased the amount of the ToxR activator
b. a drug that blocked the DNA-binding activity of the activator
c. a drug that increased rates of transcription in V. cholerae
d. a drug that increased rates of translation in V.chloerae. Answer: a
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