BIO 252 Exam 3 Questions and
Correct Answers
Which term would be applied to a regulatory condition that occurs when protein is
associated with a particular section of DNA and greatly reduces transcription?
✓✓~ negative control
In the diagram below, what type of control, positive or negative, is operating?
-{ }( )-|-structrual gene-
^
{regulatory protien}
makes a transcription.
✓✓~ positive control
T/F Under a system of positive control, transcription does not occur unless a
regulator molecule directly stimulates RNA production.
✓✓~ True
T/F Under a system of negative control, genetic expression occurs unless some form
of regulator shuts off such expression.
, ✓✓~ True
Which term is used to describe enzymes that are produced only when specific
substrates are present in the environment?
✓✓~ inducible: This term best describes enzymes that are produced only when specific
substrates are present in the environment to induce their production.
Which term refers to a contiguous genetic complex that is under coordinated control?
✓✓~ operon
Things to define
✓✓~ allosteric
lysogen
attenuation
prototroph
operon
Cryan experiments with gut microbes
16 interaction
17 interaction
Which of the following mutations could lead to constitutive expression of the genes of
the lac operon?
, ✓✓~ A mutation in the operator sequence. Such a mutation could prevent binding of the
repressor, allowing expression under all conditions.
Which of the following best describes the biological role of the lac operon?
✓✓~ It ensures that a cell dedicates resources to the production of enzymes involved in lactose
metabolism only when lactose is available in the environment. The cell expends energy to
produce the proteins necessary for lactose metabolism only when lactose is present.
T/F The placement of the operator sequence between the promotor and the
structural genes is critical to the proper function of the lac operon.
✓✓~ True. When the repressor binds to the operator, RNA polymerase cannot transcribe the
structural genes.
In the lac operon, the product of structural gene lacZ is capable of ________.
✓✓~ splitting the β-linkage of lactose
Which term most appropriately refers to a regulatory protein in prokaryotes?
✓✓~ DNA binding protein
A constitutive mutation in the lac operon may be of several types. Name two types of
constitutive mutations.
✓✓~ lacOc, lacI-
, T/F Regarding the lactose utilization system in E. coli, a constitutive mutant is one in
which the three enzymes are produced regardless of the presence or absence of
lactose.
✓✓~ True
Which of the following is a neurochemical microbes in our gut can make?
✓✓~ GABA
Experiments led by Cryan's group found that
✓✓~ Mice fed lactobacilllus were more calm, behaviorally, when measured via a 6 minutes swim
test.
When Lyte asked, "Can bacteria cause stress in mice?" he did an experiment that
measured:
✓✓~ how mice approached ledges of a maze
T/F Dr. Lyte's inital experiments linking the microbiome to behavior were immediately
ground-breaking and game-changing for the field.
✓✓~ False
Which of the following terms best characterizes catabolite repression associated with
the lac operon in E. coli?
✓✓~ positive control
Correct Answers
Which term would be applied to a regulatory condition that occurs when protein is
associated with a particular section of DNA and greatly reduces transcription?
✓✓~ negative control
In the diagram below, what type of control, positive or negative, is operating?
-{ }( )-|-structrual gene-
^
{regulatory protien}
makes a transcription.
✓✓~ positive control
T/F Under a system of positive control, transcription does not occur unless a
regulator molecule directly stimulates RNA production.
✓✓~ True
T/F Under a system of negative control, genetic expression occurs unless some form
of regulator shuts off such expression.
, ✓✓~ True
Which term is used to describe enzymes that are produced only when specific
substrates are present in the environment?
✓✓~ inducible: This term best describes enzymes that are produced only when specific
substrates are present in the environment to induce their production.
Which term refers to a contiguous genetic complex that is under coordinated control?
✓✓~ operon
Things to define
✓✓~ allosteric
lysogen
attenuation
prototroph
operon
Cryan experiments with gut microbes
16 interaction
17 interaction
Which of the following mutations could lead to constitutive expression of the genes of
the lac operon?
, ✓✓~ A mutation in the operator sequence. Such a mutation could prevent binding of the
repressor, allowing expression under all conditions.
Which of the following best describes the biological role of the lac operon?
✓✓~ It ensures that a cell dedicates resources to the production of enzymes involved in lactose
metabolism only when lactose is available in the environment. The cell expends energy to
produce the proteins necessary for lactose metabolism only when lactose is present.
T/F The placement of the operator sequence between the promotor and the
structural genes is critical to the proper function of the lac operon.
✓✓~ True. When the repressor binds to the operator, RNA polymerase cannot transcribe the
structural genes.
In the lac operon, the product of structural gene lacZ is capable of ________.
✓✓~ splitting the β-linkage of lactose
Which term most appropriately refers to a regulatory protein in prokaryotes?
✓✓~ DNA binding protein
A constitutive mutation in the lac operon may be of several types. Name two types of
constitutive mutations.
✓✓~ lacOc, lacI-
, T/F Regarding the lactose utilization system in E. coli, a constitutive mutant is one in
which the three enzymes are produced regardless of the presence or absence of
lactose.
✓✓~ True
Which of the following is a neurochemical microbes in our gut can make?
✓✓~ GABA
Experiments led by Cryan's group found that
✓✓~ Mice fed lactobacilllus were more calm, behaviorally, when measured via a 6 minutes swim
test.
When Lyte asked, "Can bacteria cause stress in mice?" he did an experiment that
measured:
✓✓~ how mice approached ledges of a maze
T/F Dr. Lyte's inital experiments linking the microbiome to behavior were immediately
ground-breaking and game-changing for the field.
✓✓~ False
Which of the following terms best characterizes catabolite repression associated with
the lac operon in E. coli?
✓✓~ positive control
