2024 BIOS252 Biology Comprehension Exam With Answers (226 Solved Questions)

Name: 2024 BIOS252 Biology Comprehension Exam With Answers (226 Solved Questions)
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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
T/F Lactose is an inducer of the lac operon. - 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? - 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? - 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 - - + (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
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 - + +
For the genotype,
I s 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
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 - + +
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 - + +
Predict the level of genetic activity of the lac operon as well as the status of the lac repressor
and the CAP protein under the cellular conditions listed in the accompanying table.
Line Lactose Glucose
(a) - -
(b) + -
(c) - +
(d) + +
line a: - The repressor is bound to the operator, and CAP is bound to its binding site. The operon is
not transcribed.
Predict the level of genetic activity of the lac operon as well as the status of the lac repressor
and the CAP protein under the cellular conditions listed in the accompanying table.
Line Lactose Glucose
(a) - -
(b) + -
(c) - +
(d) + +
line b: - The repressor is inactive, and CAP is bound to its binding site. The operon is being
transcribed at a high level.
Predict the level of genetic activity of the lac operon as well as the status of the lac repressor
and the CAP protein under the cellular conditions listed in the accompanying table.
Line Lactose Glucose
(a) - -
(b) + -
(c) - +
(d) + +

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line c: - The repressor is bound to the operator, and CAP is not bound to its binding site. The
operon is not transcribed.
Predict the level of genetic activity of the lac operon as well as the status of the lac repressor
and the CAP protein under the cellular conditions listed in the accompanying table.
Line Lactose Glucose
(a) - -
(b) + -
(c) - +
(d) + +
line d: - The repressor is inactive, and CAP is not bound to its binding site. The operon is
transcribed at a low level.
T/F In general, one could say that there are fewer levels of regulation possible in prokaryotes
than in eukaryotes. - True
Regarding eukaryotic and prokaryotic genetic regulation, what process seems to be the most
similar between the two? - transcriptional regulation
Is the binding of a transcription factor to its DNA recognition sequence necessary and sufficient
for an initiation of transcription at a regulated gene?
What else plays a role in this process? - Transcription factors are proteins that are necessary
for the initiation of transcription. However, they are not sufficient for the initiation of
transcription. Transcription factors contain at least two functional domains: one binds to the DNA
sequences of promoters and/or enhancers, while the other interacts with RNA polymerase or
other transcription factors.
What is the role of Dicer in RNA-induced gene silencing? - It cleaves longer RNAs into short,
regulatory RNA molecules. The regulatory siRNAs and miRNAs are involved in suppression of gene
expression.
T/F Alternative splicing of single mRNA transcripts gives rise to multiple mRNAs. - True.
Alternative splicing of mRNA transcripts is a process used to regulate gene expression
posttranscriptionally.
Pro or Eu:

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adapted to challenges of a single-celled existence, rapid turnover of mRNA, translation can occur
immediately after mRNA is transcribed,cis-acting regulatory proteins required for transcription
initiation, regulation of expression occurs at many checkpoints, chromatin remodeling required
for expression of many genes, introns in genes must be spliced out before mRNA is mature, most
organisms optimized for a multicellular lifestyle, DNA found in nucleus requires transport across
membranem, RNAs have various half-lives - Pro: adapted to challenges of a single-celled
existence, rapid turnover of mRNA, translation can occur immediately after mRNA is transcribed
Eu:
cis-acting regulatory proteins required for transcription initiation, regulation of expression
occurs at many checkpoints, chromatin remodeling required for expression of many genes,
introns in genes must be spliced out before mRNA is mature, most organisms optimized for a
multicellular lifestyleDNA found in nucleus requires transport across membrane, mRNAs have
various half-lives
__________________ refers to changes in DNA/chromosome structure that can influence overall
gene output - chromatin remodeling
_________ are sequences in DNA to which transcription factors and RNA polymerase bind to
initiate transcription - promoters
____________ are cis- acting DNA sequences to which transcription factors bind to regulate
transcription. They can act over distances of thousands of base pairs and can be upstream,
downstream, or internal to the gene they affect. - enhancers
cis- acting vs trans factors -
_____________ bind DNA and regulate transcription - transcription factor
The addition of a 5' cap and a poly A tail and removal of introns are all steps in
_________________ - RNA processing and transport
RNA processing contributes to ________________, which regulates translation - mRNA stability
Which of the following clusters of terms applies when addressing enhancers as elements
associated with eukaryotic genetic regulation? - cis-acting, variable orientation, variable position

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T/F Alternative RNA processing can result in different mRNAs that start with different exons. -
True
T/F Transcription in eukaryotes is generally influenced by enhancers, just as in prokaryotes. -
False
T/F Alternative RNA processing generates different mRNAs that can direct the synthesis of
different polypeptides. - True
What are transcription factors? - regulatory proteins that bind to specific DNA sequences.
Transcription factors are proteins that bind to specific DNA recognition sequences in the
promoter or enhancer elements of a gene.
Promoters vs. Enhancers:
may influence the expression of more than one gene, position can be upstream, downstream, or
within the gene,not required for basal-level transcription, responsible for tissue- and time-
specific gene expression,always upstream of the gene within 100 bases of the transcription
initiation site, TATA, CAAT, GC boxes, required for basal-level transcription - Promoters:
may influence the expression of more than one gene, position can be upstream, downstream, or
within the gene,not required for basal-level transcription, responsible for tissue- and time-
specific gene expression
Enhancers:
always upstream of the gene within 100 bases of the transcription initiation site, TATA, CAAT, GC
boxes, required for basal-level transcription
T/F Transcriptionally inactive regions of the genome are typically heavily methylated. - True.
Methylation of cytosine residues is often associated with decreased transcription levels.
Mutagenic studies of the promoter region of the β-globin gene indicate that mutations in some
areas are more likely than mutations in other areas to affect transcription rates. When mutations
occur in consensus sequences (modular elements such as GC box, CAAT box, TATA box), does
transcription increase or decrease? - decrease
For the genotype,
I + O+ Z+/ F' I + O+ Z+
which of the following should be entered into the chart?

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Genotype
I + O+ Z+/ F' I + O+ Z+
I - Oc Z-/ F' I- Oc Z-
I - Oc Z+/ F' I - O+ Z+
I s Oc Z-/ F' I s 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)
No Lactose/Lactose - - + (beta-gal made only when there is lactose)
For the genotype,
I- Oc Z-/ F' I- Oc Z-
which of the following should be entered into the chart?
Genotype
I + O+ Z+/ F' I + O+ Z+
I - Oc Z-/ F' I- Oc Z-
I - Oc Z+/ F' I - O+ Z+
I s Oc Z-/ F' I s 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)
No Lactose/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- Oc Z-

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2024 BIOS252 Biology Comprehension Exam With Answers (226 Solved Questions)

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