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MCB 150 Final Exam||Just Out!!!
Which point of gene regulation would save the most energy if a
gene product is not currently needed?
A. mRNA stability
B. Protein post-translational modification
C. Protein stability
D. mRNA synthesis
E. Allosteric regulation of the protein product - ANSWER-A.
mRNA stability
State whether each of the following statements are true or
false.
Choices: True, False.
1. In the absence of glucose, the concentration of cAMP will be
high.
2. In the absence of glucose, the concentration of CRP will be
higher than when glucose is present.
3. CRP-cAMP binds to the lac promoter, facilitating
transcription.
4. If glucose and lactose are present, the lac operon will be
undergoing positive regulation.
5. In the absence of lactose, no β-galactosidase is expressed.
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6. An example of positive regulation is lactose binding to lac
repressor.
7. Lactose binds to an allosteric site on the lac repressor
changing its conformation. - ANSWER-1. True.
2. False. In the absence of glucose, the concentration of cAMP
will be higher than when glucose is present.
3. True.
4. False. The lac operon will be undergoing both positive and
negative regulation.
5. False. In the absence of lactose, β-galactosidase is still
expressed.
6. False. An example of negative regulation is lactose binding to
lac repressor.
7. True.
If a scientist were to delete the lac Z gene what would be the
consequences if lactose were present and glucose levels were
low?
A. The lac I gene would not be transcribed.
B. Lac Y and Lac A would not be produced.
C. Lac I repressor would be continually bound to the operator.
D. The cell could not utilize lactose as a sugar source.
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E. There would be no consequences. - ANSWER-D. The cell
could not utilize lactose as a sugar source.
The cell would not be able to produce β-galactosidase.
Which of the following conditions would give the highest
induction of the Lac operon?
A. Lactose and high cAMP
B. Lactose and low cAMP
C. Lactose, glucose, and maltose
D. Glucose and arabinose
E. Glucose only - ANSWER-A. Lactose and high cAMP
Which of the following statements is false regarding the lac
operon?
A. The lac operon will always be expressed at its maximal level
as long as a bacterial cell is growing in a medium containing
lactose.
B. Without lactose, lac repressor binds to the operator region,
preventing RNA polymerase from binding to the promoter
region.
C. Only when cAMP is bound to CRP can CRP bind to the
promoter region.
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D. CRP is consitutively expressed.
E. LacI is constitutively expressed. - ANSWER-A. The lac operon
will always be expressed at its maximal level as long as a
bacterial cell is growing in a medium containing lactose.
Which one of the following genes is transcribed as a direct
component of the lac operon?
A. lac Z
B. lac O
C. lac I
D. lac E
E. lac X - ANSWER-A. lac Z
Choose true or false regarding the following statements about
the lac operon.
Choices: True, False.
1. Glucose is known as the inducer because of its ability to raise
levels of cAMP.
2. There is maximum expression of the lac operon when cAMP
is absent.
3. Binding lactose to an allosteric site on the repressor protein is
an example of positive regulation.
MCB 150 Final Exam||Just Out!!!
Which point of gene regulation would save the most energy if a
gene product is not currently needed?
A. mRNA stability
B. Protein post-translational modification
C. Protein stability
D. mRNA synthesis
E. Allosteric regulation of the protein product - ANSWER-A.
mRNA stability
State whether each of the following statements are true or
false.
Choices: True, False.
1. In the absence of glucose, the concentration of cAMP will be
high.
2. In the absence of glucose, the concentration of CRP will be
higher than when glucose is present.
3. CRP-cAMP binds to the lac promoter, facilitating
transcription.
4. If glucose and lactose are present, the lac operon will be
undergoing positive regulation.
5. In the absence of lactose, no β-galactosidase is expressed.
,2|Page
6. An example of positive regulation is lactose binding to lac
repressor.
7. Lactose binds to an allosteric site on the lac repressor
changing its conformation. - ANSWER-1. True.
2. False. In the absence of glucose, the concentration of cAMP
will be higher than when glucose is present.
3. True.
4. False. The lac operon will be undergoing both positive and
negative regulation.
5. False. In the absence of lactose, β-galactosidase is still
expressed.
6. False. An example of negative regulation is lactose binding to
lac repressor.
7. True.
If a scientist were to delete the lac Z gene what would be the
consequences if lactose were present and glucose levels were
low?
A. The lac I gene would not be transcribed.
B. Lac Y and Lac A would not be produced.
C. Lac I repressor would be continually bound to the operator.
D. The cell could not utilize lactose as a sugar source.
,3|Page
E. There would be no consequences. - ANSWER-D. The cell
could not utilize lactose as a sugar source.
The cell would not be able to produce β-galactosidase.
Which of the following conditions would give the highest
induction of the Lac operon?
A. Lactose and high cAMP
B. Lactose and low cAMP
C. Lactose, glucose, and maltose
D. Glucose and arabinose
E. Glucose only - ANSWER-A. Lactose and high cAMP
Which of the following statements is false regarding the lac
operon?
A. The lac operon will always be expressed at its maximal level
as long as a bacterial cell is growing in a medium containing
lactose.
B. Without lactose, lac repressor binds to the operator region,
preventing RNA polymerase from binding to the promoter
region.
C. Only when cAMP is bound to CRP can CRP bind to the
promoter region.
, 4|Page
D. CRP is consitutively expressed.
E. LacI is constitutively expressed. - ANSWER-A. The lac operon
will always be expressed at its maximal level as long as a
bacterial cell is growing in a medium containing lactose.
Which one of the following genes is transcribed as a direct
component of the lac operon?
A. lac Z
B. lac O
C. lac I
D. lac E
E. lac X - ANSWER-A. lac Z
Choose true or false regarding the following statements about
the lac operon.
Choices: True, False.
1. Glucose is known as the inducer because of its ability to raise
levels of cAMP.
2. There is maximum expression of the lac operon when cAMP
is absent.
3. Binding lactose to an allosteric site on the repressor protein is
an example of positive regulation.
