Deck 16: Regulation of Gene Expression

Question 1

In comparison with regulation of the production of enzymes, allosteric regulation of enzyme activity is _______ and _______ energetically efficient.

A) faster; more
B) faster; about as
C) faster; less
D) slower; more
E) slower; less

Answer 1

C

Question 2

In bacterial cells, the concentration of cAMP is _______ correlated with the concentration of glucose; hence, glucose concentrations should _______ correlated with the amount of transcription in the lac operon (assuming that lactose is abundant).

A) positively; be positively
B) positively; be inversely
C) not; not be
D) inversely; be positively
E) inversely; be inversely

Answer 2

E

Question 3

In E.coli metabolism, _______ is the preferred energy source because it is _______.

A) lactose; more abundant
B) lactose; easier to metabolize
C) glucose; more abundant
D) glucose; less abundant
E) glucose; easier to metabolize

Answer 3

E

Question 4

In a particular bacterial cell, β-galactosidase is at high concentrations but $\beta$ -galactoside permease is at very low concentrations.Which is the most likely explanation?

A) Both glucose and lactose are at high concentrations.
B) Both glucose and lactose are at low concentrations.
C) The operator has a mutation.
D) The promoter has a mutation.
E) One of the structural genes has a mutation.

Question 5

Which of the following reflects the order of operon elements, assuming transcription is occurring from left to right?

A) Operator, promoter, structural genes
B) Operator, structural genes, promoter
C) Promoter, operator, structural genes
D) Promoter, structural genes, operator
E) Structural genes, promoter, operator

Question 6

A certain operon has structural genes that encode enzymes involved in the synthesis of a glycopeptide.This system is likely to be _______, and _______ will most likely bind to the operator.

A) inducible; the glycopeptide
B) inducible; one or more molecules used in the production of the glycopeptide
C) repressible; the glycopeptide
D) repressible; one or more molecules used in the production of the glycopeptide
E) repressible; no molecules

Question 7

To be activated, the CRP must first bind

A) the repressor molecule.
B) the repressor protein.
C) the activator protein.
D) the co-repressor molecule.
E) cAMP.

Question 8

In comparison with structural genes in bacterial operons, genes that encode for stress responses in plants

A) are located closer together on the chromosome.
B) are located farther apart on the chromosome.
C) are not coordinately regulated.
D) do not alter their expression levels in response to transcription factor binding.
E) do not respond to changes in environmental conditions.

Question 9

A mutagenesis screen uncovers two discrete mutations, each for a single gene of a given operon that contains the genes that control a biosynthetic pathway.Which phenomenon would likely be observed in an organism that carries both of these mutations?

A) Partial linkage
B) Complete linkage
C) Epistasis
D) Recessive lethality
E) Complete dominance/recessiveness

Question 10

Actin, which is part of many cellular structures and has several functions, is produced at constant levels in nearly all cells.It is best described as a(n) _______ protein.

A) inducible
B) repressible
C) conditional
D) constitutive
E) regulated

Question 11

Which of the following is a carrier protein?

A) Lactose
B) β-galactoside
C) β-galactoside permease
D) β-galactoside transacetylase
E) Glucose

Question 12

Refer to the figure showing the potential points for the regulation of gene expression. Which point would be considered posttranslational control?

A) 1
B) 2
C) 3
D) 6
E) 7

Question 13

Which statement is false?

A) Operons involved in catabolism are typically inducible.
B) Operons involved in anabolism are typically repressible.
C) Constitutively expressed genes are generally unregulated.
D) Regulation of gene expression only involves control of transcription.
E) The lac repressor gene is expressed constitutively.

Question 14

If the gene encoding the lac repressor is mutated such that the repressor can no longer bind the operator, will transcription of that operon occur?

A) Yes, because the repressor transcriptionally activates the lac genes.
B) Yes, but only when lactose is present.
C) No, because RNA polymerase is needed to transcribe the genes.
D) Yes, because RNA polymerase will be able to bind the promoter and transcribe the operon.
E) No, because cAMP levels are low when the repressor is nonfunctional.

Question 15

An inducer

A) inhibits the synthesis of needed enzyme(s).
B) stimulates the synthesis of needed enzyme(s).
C) binds to the promoter and prevents the repressor from binding to the operator.
D) binds to the operator and prevents the repressor from binding at this site.
E) is the same as a promoter.

Question 16

Which is least likely to occur in a non-mutant bacterial cell?

A) $\beta$ -galactoside transacetylase is present at a high concentration when $\beta$ -galactoside is present at a low concentration.
B) $\beta$ -galactoside transacetylase is produced at very low levels in the absence of lactose.
C) $\beta$ -galactoside transacetylase is produced at very low levels when glucose is abundant.
D) $\beta$ -galactoside transacetylase is produced at high levels when lactose is at a high concentration and glucose is not available.
E) $\beta$ -galactoside transacetylase and β-galactoside are both present in very low concentrations.

Question 17

$\beta$ -galactoside transacetylase is

A) a promoter.
B) encoded by a structural gene.
C) a constitutive protein.
D) usually produced at high levels when $\beta$ -galactoside is produced at low levels.
E) usually produced at low levels when $\beta$ -galactoside is produced at high levels.

Question 18

Bacterial promoters of different housekeeping genes

A) are nearly identical throughout their sequence.
B) can vary in sequence but share consensus sequences at which they are very similar.
C) can vary in sequence but share sigma factors at which they are very similar.
D) can vary in sequence but share regulatory sequences at which they are very similar.
E) can vary in sequence and share no common motifs.

Question 19

The earlier the cell intervenes in the process of protein synthesis, the _______ energy it wastes.Thus, cells will tend to regulate protein synthesis _______.

A) more; at the earliest possible stage
B) more; at all stages
C) more; at the latest possible stage
D) less; at the earliest possible stage
E) less; at the latest possible stage

Question 20

Which event would lead to a reduction in gene expression?

A) Mutation of the DNA-binding domain of an activator, changing its shape
B) Mutation of the binding site of a co-repressor molecule within a repressor protein
C) Removal of all methylation marks from a region of DNA
D) Remodeling of the chromatin environment, resulting in removal of histone octamers from a gene's promoter region
E) Mutation of a TATA box to create a tighter binding of RNA polymerase to the DNA

Question 21

Sigma factors bind to

A) promoters with no specificity.
B) specific types of promoters.
C) repressors.
D) co-repressors.
E) RNA polymerases.

Question 22

Inducible and repressible systems are similar in that

A) in both systems the regulatory molecules function by binding to the operator.
B) both systems usually control biosynthetic pathways.
C) both systems usually control catabolic pathways.
D) both systems block transcription through the presence of a regulatory protein.
E) both systems are unique to prokaryotes.

Question 23

In a repressible operon, the repressor molecule

A) is the substrate of the metabolic pathway.
B) can repress the transcription of the operon on its own.
C) is a molecule made from the operon.
D) binds to the mRNA.
E) must be activated by a co-repressor.

Question 24

Catabolite repression would least likely be found in a metabolic network

A) involved in breaking down sugars.
B) involved in breaking down lipids.
C) involved in the production of an enzyme.
D) in Gram-positive bacteria.
E) in Gram-negative bacteria.

Question 25

The TATA box is a(n)

A) sequence in the promoter region of many genes.
B) square-shaped sequence.
C) enhancer consensus sequence.
D) activator sequence necessary for proper translation.
E) transcription factor.

Question 26

Refer to the figure showing the initiation of transcription in eukaryotes. Which represents the regulatory sequence of the DNA?

A) TATAT
B) ATATA
C) TFIID
D) BFEH
E) TFIID + B

Question 27

Which is an example of regulation of eukaryotic transcription?

A) Iron binding the repressor protein for the ferritin mRNA and increasing ferritin expression
B) Proteasome breakdown of protein-polyubiquitin complexes
C) MicroRNAs binding their target mRNA and causing its degradation
D) Alternative splicing of an mRNA transcript
E) Activator proteins binding an enhancer

Question 28

If the gene encoding the trp repressor is mutated such that the repressor can no longer bind tryptophan but can still bind the operon, will transcription of the trp operon occur?

A) Yes, because the trp repressor can bind the trp operon and block transcription only when it is bound to tryptophan.
B) No, because this mutation does not affect the part of the repressor that can bind the operator.
C) No, because the trp operon is repressed only when tryptophan levels are high.
D) Yes, because the trp operon can allosterically regulate the enzymes needed to synthesize the amino acid tryptophan.
E) No, because the repressor will be continuously bound to the operator.

Question 29

Refer to the figure showing the initiation of transcription in eukaryotes. Which transcription factor(s) bind(s) directly to DNA?

A) B
B) F
C) E and H
D) TFIID
E) B and H

Question 30

A DNA sequence is several thousands of nucleotides distant from the promoter.When this sequence is bound by a protein, transcription rates increase greatly.This sequence is most likely a(n)

A) TATA box.
B) enhancer.
C) operon.
D) promoter.
E) consensus sequence.

Question 31

What is the main difference between general and specific transcription factors?

A) Specific transcription factors are found only in multicellular animals, whereas general transcription factors are found in most eukaryotes.
B) Specific transcription factors are found only in multicellular plants, whereas general transcription factors are found in most eukaryotes.
C) Specific transcription factors bind to regulatory sequences of fewer genes than general transcription factors do.
D) Specific transcription factors bind regulatory sequences more tightly than general transcription factors do.
E) Specific transcription factors bind regulatory sequences less tightly than general transcription factors do.

Question 32

Refer to the figure showing the initiation of transcription in eukaryotes. From the figure it can be concluded that

A) all transcription factors work alone to initiate transcription.
B) some transcription factors bind directly to DNA.
C) TFIID binds to the promoter at the TATA box after transcription factors B and F have altered its shape.
D) protein-coding genes contain noncoding sequences.
E) RNA polymerase II independently binds to the promoter and initiates transcription.

Question 33

When an enhancer is bound, it

A) increases the stability of a specific mRNA.
B) stimulates transcription of a specific gene.
C) stimulates transcription of nearly all genes.
D) stimulates splicing of a specific mRNA.
E) stimulates splicing of nearly all mRNAs.

Question 34

A certain enzyme is synthesized whenever the solution in which some cells are growing lacks substance X.This phenomenon is most likely an example of a(n) _______ system.

A) inducible
B) positive
C) negative
D) repressible
E) positive-negative

Question 35

If a mutation in a silencer makes it much harder for proteins to bind to it, which is most likely to occur?

A) A specific gene near the silencer will be transcribed all the time, even when not needed.
B) There will be a large decrease in transcription rates for most genes.
C) There will be a large increase in transcription rates for most genes.
D) The rate of transcription of a specific gene located near the silencer will be reduced, even when it is needed the most.
E) Transcription will be terminated prematurely.

Question 36

The trp operon

A) codes for proteins needed for tryptophan synthesis.
B) codes for proteins needed to metabolize tryptophan.
C) is activated by the presence of tryptophan.
D) is inducible by tryptophan.
E) is inducible by lactose (or allolactose).

Question 37

How do negative regulation and positive regulation in bacteria differ?

A) Only negative regulation involves promoters.
B) Only positive regulation involves promoters.
C) Only in negative regulation is transcription reduced when the regulatory complex binds to the promoter.
D) Only in positive regulation is transcription reduced when the regulatory complex binds to the promoter.
E) Positive regulation must occur at an earlier stage than negative regulation.

Question 38

Helix-turn-helix is a _______ found in a _______.

A) structural motif; promoter
B) structural motif; transcription factor
C) consensus sequence; promoter
D) consensus sequence; enhancer
E) consensus sequence; transcription factor

Question 39

Which statement about TFIID is false?

A) It is the first transcription factor to bind to the TATA box.
B) Its shape changes after it binds to the TATA box.
C) It attracts other transcription factors to the transcription initiation complex.
D) It is a specific transcription factor.
E) It is not sufficient to activate RNA polymerase II by itself.

Question 40

In a fruit fly, the transcription rates of a gene that codes for an enzyme vary tremendously among different cell types.The most likely reason for these differences is that different cell types have different

A) promoters.
B) inducers.
C) transcription factors present.
D) silencers.
E) enhancers.

Question 41

If a loss-of-function mutation occurs in one of the early genes in a lytic bacteriophage, which change is most likely to occur?

A) Late genes will be turned on.
B) The host genes will remain turned on.
C) The viral genome will be replicated.
D) New viral capsid proteins will be produced.
E) Proteins that lyse the host cell will be produced.

Question 42

Cro is a bacteriophage λ protein that represses transcription of cI but promotes expression of genes that encourage the lytic cycle.cI protein represses Cro transcription but promotes expression of genes that encourage lysogeny.If the environment experienced by bacteriophage λ deteriorates, the change will most likely _______ the lifespan of cI protein.This result will have the effect of _______.

A) increase; maintaining lysogeny
B) increase; increasing the production of capsid proteins
C) increase; making entry into the lytic phase more likely
D) decrease; maintaining lysogeny
E) decrease; making entry into the lytic phase more likely

Question 43

Eukaryotic gene regulation differs from prokaryotic gene regulation in that

A) there is no negative control in eukaryotes.
B) there is no positive control in prokaryotes.
C) there is no negative control in prokaryotes.
D) transcription and translation occur at the same location in eukaryotes, but at different locations in prokaryotes.
E) transcription and translation occur at the same location in prokaryotes, but at different locations in eukaryotes.

Question 44

How does regulation of stress response proteins in plants differ from regulation of enzymes produced from a bacterial operon?

A) Expression of stress response proteins is coordinately regulated; expression of bacterial operon genes is not.
B) Expression of bacterial operon genes is coordinately regulated; expression of stress response proteins is not.
C) Regulation of stress response proteins involves DNA-protein interactions; regulation of bacterial operon genes does not.
D) Regulation of bacterial operon genes involves DNA-protein interactions; regulation of stress response proteins does not.
E) Stress response genes are found in various locations throughout the plant genome; bacterial operon genes are found in one unit.

Question 45

In a bacteriophage undergoing a lytic phase, the early gene products _______ the host genes and _______ the late genes.

A) stimulate; stimulate
B) stimulate; have no effect on
C) stimulate; inhibit
D) inhibit; stimulate
E) inhibit; inhibit

Question 46

If you wanted to build a complex organism with differentiated cells, which type of molecule would not help achieve that goal?

A) General transcription factors
B) Varied RNA polymerases
C) Nuclear envelopes
D) Operons
E) Specific transcription factors

Question 47

The TATA box in eukaryotes is most similar to _______ in prokaryotes.

A) sigma factors
B) the entire promoter
C) a consensus sequence in the promoter
D) an operator
E) an inducer

Question 48

Viruses are

A) cells containing DNA and protein.
B) larger than most bacteria.
C) acellular.
D) able to take in nutrients and expel wastes.
E) mutated forms of DNA.

Question 49

With respect to bacteria, the term "lysogeny" refers to

A) the stable integration of bacteriophage DNA into the bacterial chromosome.
B) the excision of bacteriophage DNA from the bacterial chromosome.
C) the lysing of a bacterium by a bacteriophage.
D) mutation induced by a bacteriophage.
E) the reciprocal exchange of genetic material between a bacteriophage and a bacterium.

Question 50

Which is an anti-HIV treatment that works by preventing the formation of provirus?

A) Integrase inhibitors
B) Protease inhibitors
C) Reverse transcriptase inhibitors
D) Tat
E) Capsid

Question 51

What is the difference between a prophage and a provirus, based on what you know about HIV and bacteriophage $\lambda$ ?

A) The host of a prophage is a bacterium, whereas the host of a provirus is a eukaryote.
B) A provirus is in lysogeny, whereas a prophage is the provirus after a return to the lytic phase.
C) A prophage is in lysogeny, whereas a provirus is the prophage after a return to the lytic phase.
D) The host of a prophage is a eukaryote, whereas the host of a provirus is a bacterium.
E) A prophage is regulated by early genes, whereas a provirus is regulated by late genes.

Question 52

Which item is not used by a bacteriophage to generate new viral particles?

A) A promoter sequence that is compatible with the host RNA polymerase
B) Genes for proteins that inhibit host transcription
C) Genes for capsid proteins
D) Nucleases
E) Genes for viral RNA polymerase

Question 53

The stress response elements in plants are

A) transcription factors.
B) inducers.
C) RNA sequences.
D) enzymes.
E) DNA sequences.

Question 54

Cro is a phage protein that represses transcription of cI but promotes expression of genes that encourage the lytic cycle.cI protein represses Cro transcription but promotes expression of genes that encourage lysogeny.A mutation in Cro decreases its expression.This mutation would make entering lysogeny _______ likely.A mutation that decreases the expression of cI would have _______ effect on the likelihood of the virus entering lysogeny.

A) more; a similar
B) more; no
C) more; the opposite
D) less; a similar
E) less; the opposite

Question 55

Which action would not affect gene expression in a eukaryotic cell?

A) Deletion of a promoter
B) Deletion of an enhancer
C) Lack of modification of the cap structure on mRNA
D) Inability of a transcription factor to bind the promoter
E) Deletion of a DNA ori site

Question 56

Gene regulation by tat in HIV occurs at the level of

A) transcription initiation.
B) transcription elongation.
C) mRNA stability.
D) translation initiation.
E) translation elongation.

Question 57

Which of the following is a strategy that a virus could use in order to ensure viral reproduction in the host cell?

A) Production of tat protein, which allows viral mRNA elongation
B) Production of protease inhibitors, which block posttranslational processing
C) Use of integrase inhibitors, which prevent the viral genome from inserting into the host genome
D) Use of reverse transcriptase inhibitors, which block viral DNA synthesis from RNA
E) Carrying ribosomes for quick viral RNA translation

Question 58

Early genes of a lytic bacteriophage are transcribed by

A) late genes.
B) viral RNA polymerase from earlier lytic cycles.
C) host DNA polymerase.
D) host RNA polymerase.
E) reverse transcriptase.

Question 59

How does gene regulation differ between prokaryotes and multicellular eukaryotes?

A) Different cells vary in the types and number of genes they express in eukaryotes but not in prokaryotes.
B) Protein-DNA interactions occur only in eukaryotes.
C) Protein-DNA interactions occur only in prokaryotes.
D) Cell-specific gene expression and protein-DNA interactions both occur only in eukaryotes.
E) Cell-specific gene expression and protein-DNA interactions both occur only in prokaryotes.

Question 60

If HIV is mutated such that its tat protein is less able to bind to mRNA, the most likely result will be

A) more initiation of transcription.
B) less initiation of transcription.
C) the termination of more partial transcripts, and thus the making of fewer complete transcripts.
D) the termination of fewer partial transcripts, and thus the making of more complete transcripts.
E) a reduction in the stability of complete transcripts.

Question 61

Methylation most often occurs to _______ that are next to _______.

A) adenines; cytosines
B) adenines; guanines
C) cytosines; adenines
D) cytosines; guanines
E) guanines; adenines

Question 62

Imagine that the promoter for gene X becomes highly methylated.How will this affect the expression of gene X?

A) There will be no effect.
B) Gene X will be transcribed but not translated.
C) Gene X will be transcribed if the transcription factors receive the appropriate environmental signal.
D) Gene X will not be transcribed or translated.
E) Gene X will be transcribed if the histones become acetylated.

Question 63

If a mutation causes a decrease in the activity of histone acetyltransferases, histones will most likely have a _______ affinity for DNA, and there will be _______ in transcription rates.

A) greater; an increase
B) greater; a decrease
C) reduced; an increase
D) reduced; no change
E) reduced; a decrease

Question 64

Heterochromatin stains _______ than euchromatin and is _______ transcriptionally active.

A) darker; more
B) darker; just as
C) darker; less
D) lighter; more
E) lighter; less

Question 65

If a mutation causes a reduction in the production of demethylase, the expected effect will be _______ in the amount of overall methylation and therefore _______ in overall gene expression.

A) an increase; an increase
B) an increase; a decrease
C) no change; an increase
D) a decrease; an increase
E) a decrease; a decrease

Question 66

If each interphase nucleus in 100 epithelial cells from a rat contains a single Barr body, one can conclude that

A) the cells have an excess of DNA methyltransferase.
B) the cells have a deficiency of DNA methyltransferase.
C) all of the chromatin in these cells is inactive.
D) the cells came from a male rat.
E) the cells came from a female rat.

Question 67

One of the genes that is known to be transcribed from the inactive X chromosome is

A) Xist.
B) ZIST.
C) the gene that encodes inactivation controller protein.
D) the gene that encodes DNA methyltransferase.
E) methyl-X.

Question 68

Nucleosomes disaggregate (or "open") to allow transcription and then reaggregate

A) through alternative splicing.
B) by methylation and demethylation.
C) through alternation of nucleotides.
D) by acetylation and deacetylation.
E) through insertion of nucleotides.

Question 69

Which enzyme allows methylation changes to be passed on after DNA replication?

A) Demethylase
B) DNA methyltransferase
C) Methylheritablase
D) Maintenance methylase
E) CpG

Question 70

Imagine that gene X is in a chromosome region where the histones are highly acetylated.How will this affect its expression?

A) There will be no effect.
B) It will be transcribed but not translated.
C) It will be transcribed if the transcription factors receive the appropriate environmental signal.
D) It will not be transcribed or translated.
E) It will be transcribed if the histones become deacetylated.

Question 71

Refer to the figure showing the potential points for the regulation of gene expression. Which point would be considered epigenetic control?

A) 1
B) 2
C) 3
D) 4
E) 5

Question 72

Consider the following statement: Histone deacetylases tend to decrease transcription from particular genes.Is it true or false, and for what reason?

A) True, because acetylated histones have higher affinity for DNA
B) True, because acetylated histones have lower affinity for DNA
C) False, because acetylated histones have higher affinity for DNA
D) False, because acetylated histones have lower affinity for DNA
E) False, because acetylation status of histones has no bearing on transcription

Question 73

The activity of _______ tends to lead to increased transcription.

A) histone deacetylase
B) histone acetyltransferase
C) DNA methyltransferase
D) maintenance methylase
E) RNA polymerase

Question 74

Which statement about epigenetics is false?

A) One type of epigenetic change occurs via DNA methylation.
B) One type of epigenetic change occurs via chromosomal protein alterations.
C) Epigenetic changes can lead to gene expression changes.
D) Epigenetic changes do not change the DNA sequence.
E) DNA methylation can prevent binding of repressor proteins, resulting in increased gene expression.

Question 75

The Barr body indicates

A) X chromosome inactivation.
B) cell death.
C) genomic imprinting.
D) posttranslational control of eukaryotic gene expression.
E) stress response.

Question 76

The expression of some genes can be regulated in part by the pattern of RNA splicing.This is an example of

A) DNA methylation.
B) transcriptional regulation.
C) pretranscriptional control.
D) posttranscriptional control.
E) genomic imprinting.

Question 77

The addition of acetyl groups makes histones _______ positively charged, and thus _______ their affinity for DNA.

A) more; increases
B) more; decreases
C) less; increases
D) less; has no effect on
E) less; decreases

Question 78

Identical twins show

A) similar methylation patterns throughout their lives.
B) similar methylation patterns as children but divergent patterns as adults.
C) divergent methylation patterns as children but similar patterns as adults.
D) divergent methylation patterns as children, similar patterns as teenagers, and divergent patterns as adults.
E) divergent methylation patterns throughout their lives.

Question 79

Two identical twins showed very similar methylation patterns when they were 4 years old, but these patterns diverged considerably by the time they were 40 years old.What is the most likely explanation for this?

A) It is an effect of different genomic imprinting in the twins.
B) It is due to different alternative splicing in the twins.
C) It is due to the twins experiencing different environments as adults.
D) It is due to different levels of histone acetyltransferase in the twins.
E) It is due to differences the twins experienced in utero.

Question 80

In teenage children of women who suffered physical abuse while pregnant, the glucocorticoid receptor has a promoter region

A) with more methylated bases than are typical.
B) with fewer methylated bases than are typical.
C) without epigenetic changes.
D) with more euchromatin than is typical.
E) with more heterochromatin than is typical.