ASU BIO 340 Exam
3 Questions and
Complete Solutions
Graded A+
Denning [Date] [Course title]
, What will be the effect on transcription when an inhibitor is in play?
A. Allow transcription B. Prevent transcription - Correct Ans: B Explanation: An inhibitor prevents
activator from binding to DNA; activators are used in positive regulation (increasing transcription) - thus,
the inhibitor prevents the activator from positive regulating (increasing) transcription.
What will be the effect on transcription when an inducer is in play?
A. Allow transcription B. Prevent transcription - Correct Ans: A Explanation: When an inducer is in play,
it will allow transcription.
For a gene under positive control, which of the following would prevent transcription?
A. Repressor B. Corepressor C. Inducer D. Effector E. Inhibitor - Correct Ans: E Explanation: Positive
regulation includes activators (affected by effectors and inhibitors); inhibitors prevent activator from
binding to DNA, thus preventing transcription.
For a gene under negative control, which of the following would you expect to find bound to the
repressor if there is active transcription? A. Repressor B. Corepressor C. Inducer D. Effector E. Inhibitor -
Correct Ans: C Explanation: In negative regulation, there are repressors (affected by correpressors and
inducers). If there were a corepressor, the repressor would successfully bind to the operator and
prevent transcription. Inducers, however, prevent the binding of the repressor - thus causing a
prevention of it doing its job, and allowing transcription.
Which molecule serves as the inducer for the lac operon?
A. cAMP B. Glucose C. Lactose D. Allolactose - Correct Ans: D Explanation: Allolactose is the molecule
that binds to repressor protein, making it unable to bind to the operator.
Which of the following conditions will result in the greatest levels of transcription of the lac operon?
A. Lactose absent, glucose absent B. Lactose absent, glucose present C. Lactose present, glucose present
D. Lactose present, glucose absen - Correct Ans: D Explanation: From the perspective of the cell, it is
most efficient to repress expression of the genes allowing for metabolism of lactose when it's absent, to
allow it when present, but only to prioritize it when glucose (the preferred food source) is absent. In C,
allolactose will also be present, allowing transcription, but positive regulation (i.e. increase in
transcription) only happens as in D, when glucose is absent.
Which of the following mutations will result in the lowest level of transcription of the lac operon when
lactose is present?
3 Questions and
Complete Solutions
Graded A+
Denning [Date] [Course title]
, What will be the effect on transcription when an inhibitor is in play?
A. Allow transcription B. Prevent transcription - Correct Ans: B Explanation: An inhibitor prevents
activator from binding to DNA; activators are used in positive regulation (increasing transcription) - thus,
the inhibitor prevents the activator from positive regulating (increasing) transcription.
What will be the effect on transcription when an inducer is in play?
A. Allow transcription B. Prevent transcription - Correct Ans: A Explanation: When an inducer is in play,
it will allow transcription.
For a gene under positive control, which of the following would prevent transcription?
A. Repressor B. Corepressor C. Inducer D. Effector E. Inhibitor - Correct Ans: E Explanation: Positive
regulation includes activators (affected by effectors and inhibitors); inhibitors prevent activator from
binding to DNA, thus preventing transcription.
For a gene under negative control, which of the following would you expect to find bound to the
repressor if there is active transcription? A. Repressor B. Corepressor C. Inducer D. Effector E. Inhibitor -
Correct Ans: C Explanation: In negative regulation, there are repressors (affected by correpressors and
inducers). If there were a corepressor, the repressor would successfully bind to the operator and
prevent transcription. Inducers, however, prevent the binding of the repressor - thus causing a
prevention of it doing its job, and allowing transcription.
Which molecule serves as the inducer for the lac operon?
A. cAMP B. Glucose C. Lactose D. Allolactose - Correct Ans: D Explanation: Allolactose is the molecule
that binds to repressor protein, making it unable to bind to the operator.
Which of the following conditions will result in the greatest levels of transcription of the lac operon?
A. Lactose absent, glucose absent B. Lactose absent, glucose present C. Lactose present, glucose present
D. Lactose present, glucose absen - Correct Ans: D Explanation: From the perspective of the cell, it is
most efficient to repress expression of the genes allowing for metabolism of lactose when it's absent, to
allow it when present, but only to prioritize it when glucose (the preferred food source) is absent. In C,
allolactose will also be present, allowing transcription, but positive regulation (i.e. increase in
transcription) only happens as in D, when glucose is absent.
Which of the following mutations will result in the lowest level of transcription of the lac operon when
lactose is present?
