BIO 252 Exam 3 UPDATED ACTUAL
Exam 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? - CORRECT
ANSWER - negative control
In the diagram below, what type of control, positive or negative, is operating?
-{ }( )-|-structrual gene-
^
{regulatory protien}
makes a transcription. - CORRECT ANSWER - positive control
T/F Under a system of positive control, transcription does not occur unless a regulator molecule
directly stimulates RNA production. - CORRECT ANSWER - True
T/F Under a system of negative control, genetic expression occurs unless some form of regulator
shuts off such expression. - CORRECT ANSWER - True
Which term is used to describe enzymes that are produced only when specific substrates are
present in the environment? - CORRECT ANSWER - 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? -
CORRECT ANSWER - operon
Things to define - CORRECT ANSWER - 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? - CORRECT ANSWER - 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? - CORRECT
ANSWER - 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. - CORRECT ANSWER - 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 ________. - CORRECT
ANSWER - splitting the β-linkage of lactose
Which term most appropriately refers to a regulatory protein in prokaryotes? - CORRECT
ANSWER - DNA binding protein
A constitutive mutation in the lac operon may be of several types. Name two types of
constitutive mutations. - CORRECT ANSWER - 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. - CORRECT
ANSWER - True
Which of the following is a neurochemical microbes in our gut can make? - CORRECT
ANSWER - GABA
Experiments led by Cryan's group found that - CORRECT ANSWER - 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: -
CORRECT ANSWER - 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. - CORRECT ANSWER - False
Which of the following terms best characterizes catabolite repression associated with the lac
operon in E. coli? - CORRECT ANSWER - positive control
T/F Lactose is an inducer of the lac operon. - CORRECT ANSWER - True. Lactose
indirectly induces or stimulates the transcription of genes involved in its metabolism.
What would be the effect of a mutation in the lacI gene that prevented the repressor from binding
to lactose? - CORRECT ANSWER - The lac Z, Y, and A genes would not be expressed. If
lactose could not bind to the repressor, the repressor would stay bound to the operator and
repress the transcription of the lac Z, Y, and A genes.
What is the role of glucose in catabolite repression? - CORRECT ANSWER - It decreases
the levels of cAMP in the cell, repressing transcription from the lac operon.Glucose decreases
the levels of cAMP in the cell, preventing formation of the CAP-cAMP complexes necessary for
the stimulation of transcription from the lac operon.
, For the genotype,
I + O+ Z+/ F' I - O+ Z+
which of the following should be entered into the chart?
Genotype
I + O+ Z+/ F' I - O+ Z+
I - Oc Z+/ F'I - O+ Z-
I s Oc Z+/ F'I + O+ Z+
I - O+ Z+/ F' I - O+ Z+
I+ = wild-type repressor
I- = mutant repressor (unable to bind to the operator)
Is = mutant repressor (insensitive to lactose)
O+ = wild-type operator
Oc = constitutive operator (insensitive to repressor)
lactose or no lactose in chart - CORRECT ANSWER - - + (beta gal made when there is
lactose)
For the genotype,
I - Oc Z+/ F'I - O+ Z-
which of the following should be entered into the chart?
Genotype
I + O+ Z+/ F' I - O+ Z+
I - Oc Z+/ F'I - O+ Z-
I s Oc Z+/ F'I + O+ Z+
I - O+ Z+/ F' I - O+ Z+
I+ = wild-type repressor
Exam 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? - CORRECT
ANSWER - negative control
In the diagram below, what type of control, positive or negative, is operating?
-{ }( )-|-structrual gene-
^
{regulatory protien}
makes a transcription. - CORRECT ANSWER - positive control
T/F Under a system of positive control, transcription does not occur unless a regulator molecule
directly stimulates RNA production. - CORRECT ANSWER - True
T/F Under a system of negative control, genetic expression occurs unless some form of regulator
shuts off such expression. - CORRECT ANSWER - True
Which term is used to describe enzymes that are produced only when specific substrates are
present in the environment? - CORRECT ANSWER - 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? -
CORRECT ANSWER - operon
Things to define - CORRECT ANSWER - 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? - CORRECT ANSWER - 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? - CORRECT
ANSWER - 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. - CORRECT ANSWER - 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 ________. - CORRECT
ANSWER - splitting the β-linkage of lactose
Which term most appropriately refers to a regulatory protein in prokaryotes? - CORRECT
ANSWER - DNA binding protein
A constitutive mutation in the lac operon may be of several types. Name two types of
constitutive mutations. - CORRECT ANSWER - 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. - CORRECT
ANSWER - True
Which of the following is a neurochemical microbes in our gut can make? - CORRECT
ANSWER - GABA
Experiments led by Cryan's group found that - CORRECT ANSWER - 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: -
CORRECT ANSWER - 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. - CORRECT ANSWER - False
Which of the following terms best characterizes catabolite repression associated with the lac
operon in E. coli? - CORRECT ANSWER - positive control
T/F Lactose is an inducer of the lac operon. - CORRECT ANSWER - True. Lactose
indirectly induces or stimulates the transcription of genes involved in its metabolism.
What would be the effect of a mutation in the lacI gene that prevented the repressor from binding
to lactose? - CORRECT ANSWER - The lac Z, Y, and A genes would not be expressed. If
lactose could not bind to the repressor, the repressor would stay bound to the operator and
repress the transcription of the lac Z, Y, and A genes.
What is the role of glucose in catabolite repression? - CORRECT ANSWER - It decreases
the levels of cAMP in the cell, repressing transcription from the lac operon.Glucose decreases
the levels of cAMP in the cell, preventing formation of the CAP-cAMP complexes necessary for
the stimulation of transcription from the lac operon.
, For the genotype,
I + O+ Z+/ F' I - O+ Z+
which of the following should be entered into the chart?
Genotype
I + O+ Z+/ F' I - O+ Z+
I - Oc Z+/ F'I - O+ Z-
I s Oc Z+/ F'I + O+ Z+
I - O+ Z+/ F' I - O+ Z+
I+ = wild-type repressor
I- = mutant repressor (unable to bind to the operator)
Is = mutant repressor (insensitive to lactose)
O+ = wild-type operator
Oc = constitutive operator (insensitive to repressor)
lactose or no lactose in chart - CORRECT ANSWER - - + (beta gal made when there is
lactose)
For the genotype,
I - Oc Z+/ F'I - O+ Z-
which of the following should be entered into the chart?
Genotype
I + O+ Z+/ F' I - O+ Z+
I - Oc Z+/ F'I - O+ Z-
I s Oc Z+/ F'I + O+ Z+
I - O+ Z+/ F' I - O+ Z+
I+ = wild-type repressor
