Deck 11: Regulation of Gene Expression

Question 1

If glucose and lactose are both abundant,would it be beneficial for E.coli cells to express the genes that metabolize lactose? Why or why not?

A) Yes,because bacteria require both glucose and lactose.
B) Yes,because it is easier for bacteria to metabolize lactose than glucose.
C) Yes,because three proteins are required for the uptake and metabolism of lactose.
D) No,because lactose metabolism requires an inducer.
E) No,because lactose is broken down into glucose,which is already abundant.

Answer 1

E

Question 2

In which of these pairs do the two entities act in opposite ways?

A) A constitutive gene and an activator
B) A transcription factor and a constitutive gene
C) A repressor and an activator
D) A promoter and a repressor
E) A promoter and an activator

Answer 2

C

Question 3

Which of the following is least likely to be observed in a nonmutant bacterial cell?

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

Answer 3

Presence of $\beta$ -galactoside transacetylase at a high concentration when $\beta$ -galactoside is present at a low concentration

Question 4

The lac operon of E.coli consists of

A) a promoter and an operator.
B) an operator and three structural genes.
C) three structural genes and a promoter.
D) a promoter,an operator,and three structural genes.
E) a promoter,a director,and two structural genes.

Question 5

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) binds to the termination codons and allows protein synthesis to continue.

Question 6

In negative regulation,

A) the gene is never transcribed.
B) the gene is always transcribed.
C) the binding of an activator stimulates transcription.
D) transcription can be turned off when a repressor binds to the DNA near the promoter.
E) a transcription factor is required in order for the gene to be transcribed.

Question 7

Which level is not a potential point of regulation of gene expression?

A) The level of transcription
B) The level of processing mRNA
C) The level of mRNA stability
D) The level of translation
E) The level of protein export

Question 8

In a bacterial cell, $\beta$ -galactosidase is at high concentrations but $\beta$ -galactoside permease is at very low concentrations.What 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 9

A normal E.coli cell that is grown for several hours in the presence of glucose alone will show _______ levels of the protein $\beta$ -galactoside permease.A normal E.coli cell grown for several hours in the presence of lactase alone will show _______ levels of the protein $\beta$ -galactoside permease.

A) extremely low;high
B) extremely low;extremely low
C) high;extremely low
D) high;high
E) high;variable

Question 10

Actin,a protein found in almost all eukaryotic cells,is expressed in most cell types at a fairly constant level.Thus,the gene that codes for actin can be considered a(n)_______ gene.

A) inducible
B) activated
C) repressible
D) constitutive
E) transcription factor

Question 11

What kind of mutation would lead to an increase in the expression (or inappropriate expression)of a gene?

A) A mutation that lowers the efficiency of a repressor of the gene
B) A mutation that lowers the efficiency of an activator of the gene
C) A mutation that increases the efficiency of a repressor of the gene
D) A mutation that mutates an activator for the gene such that promoter recognition decreases
E) A mutation that mutates a repressor for the gene such that promoter recognition increases

Question 12

Which statement about prokaryotes is true?

A) They generally live in static environments.
B) The most efficient means of regulation of gene expression in these organisms is usually at the posttranslational level.
C) By making certain proteins only when needed,they save energy and other resources.
D) They lack the ability to react to their environment through gene expression.
E) They lack the ability to regulate their gene expression.

Question 13

The most efficient means of regulating protein synthesis in bacteria usually is by

A) selective blocking of transcription.
B) translation of the mRNA.
C) inhibition of the protein.
D) degradation of the protein.
E) transcription of the gene.

Question 14

A transcription factor is a _______ that binds to _______.

A) protein;DNA
B) protein;RNA
C) promoter;a protein
D) gene;DNA
E) gene;RNA

Question 15

Which statement about transcription factors is true?

A) All transcription factors are repressors.
B) All transcription factors are activators.
C) A promoter is a transcription factor.
D) A transcription factor can be an activator or a repressor.
E) A transcription factor can be both an activator and a repressor.

Question 16

Cyclic AMP,CREB,and protein kinase A are all in the same pathway.What is the correct sequence of these molecules in that pathway (from earliest to latest)?

A) Cyclic AMP,CREB,protein kinase A
B) Cyclic AMP,protein kinase A,CREB
C) CREB,cyclic AMP,protein kinase A
D) CREB,protein kinase A,cyclic AMP
E) Protein kinase A,CREB,cyclic AMP

Question 17

Which enzyme is required to bring lactose into E.coli cells?

A) $\beta$ -Galactoside permease
B) $\beta$ -Galactoside transferase
C) $\beta$ -Galactoside transacetylase
D) $\beta$ -Galactosidase
E) Lactase

Question 18

The expression of the gene that encodes cyclin A varies considerably across the cell cycle,reaching a peak at the G2 phase.No other gene is similarly expressed.Based on this information,one can conclude that cyclin A is

A) a transcription factor.
B) encoded by a constitutive gene.
C) encoded by an inducible gene.
D) part of an operon.
E) part of a replicon.

Question 19

CREB is a transcription factor that regulates gene expression.It binds to DNA and activates promoters of genes involved in addictive behaviors.Researchers who compared CREB levels in the brains of a strain of rats called P rats and wild-type rats found that when P rats consumed alcohol,

A) the total levels of CREB increased.
B) the total levels of CREB decreased.
C) the total levels of CREB remained the same.
D) levels of phosphorylated CREB increased.
E) levels of phosphorylated CREB decreased.

Question 20

Which change would lead to a decrease in the expression of a gene?

A) More expression of an activator of the gene
B) More expression of an activator of a repressor of the gene
C) Less expression of a repressor of the gene
D) Less expression of an activator of a repressor for the gene
E) More expression of an activator of an activator for the gene

Question 21

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) reverse transcriptase.
E) host RNA polymerase.

Question 22

What is the primary mechanism (or timing)involved in the shutdown of the host gene expression that occurs in bacteria infected by phage T4?

A) The host genes are turned off because the phage encodes repressors shutting off the host genes.
B) The host genes are turned off because the phage polymerase competes with the host polymerase.
C) The host genes are turned off because the phage interferes with activators required for production of host genes.
D) The shutdown of host gene expression occurs after transcription.
E) The shutdown of host gene expression occurs after translation.

Question 23

Which statement about virions is true?

A) They are produced only in the lysogenic phase.
B) They are produced only in the lytic phase.
C) They are the host genes shut down by the virus.
D) They are produced in the lysogenic and lytic phases.
E) They are short,unused pieces of RNA in the viral genome.

Question 24

Which statement about viruses is true?

A) They are not cells.
B) They can regulate the movements of substances into and out of the cell.
C) They can reproduce outside living cells.
D) They are large and therefore easy to study.
E) They are the smallest life form.

Question 25

Suppose that there is a mutation in the lac operon that prevents the repressor from binding to the operator.In the absence of lactose (or allolactose),the genes of the operon will be _______.In the presence of lactose (or allolactose),the genes will be _______.

A) on;on
B) on;off
C) off;on
D) off;off
E) None of the above;in both cases the presence or absence of the corepressor would dictate whether the genes are on or off.

Question 26

The prokaryotic gene zest5 produces a hypothetical enzyme and is regulated along with other genes that produce other enzymes in the pathway.From the information given,we can conclude that zest5 is a(n)_______ gene.

A) inducible
B) repressible
C) structural
D) regulatory
E) Both a and c

Question 27

Viruses

A) arise from preexisting viruses.
B) replicate their DNA before they reproduce.
C) develop and reproduce only within the cells of hosts.
D) cannot replicate themselves.
E) replicate themselves by division,just as cells do.

Question 28

In eukaryotic cells,promoters are

A) transcribed.
B) transcribed and translated.
C) sequences of RNA that are spliced out.
D) transcribed and then removed.
E) neither transcribed nor translated.

Question 29

Which statement about operons is false?

A) The structural genes in the operon are either all on or all off at a given time.
B) They consist of a cluster of genes with a single promoter.
C) Their DNA is transcribed into a single molecule of mRNA.
D) They are the units of transcriptional regulation in prokaryotes.
E) A repressible operon is turned off unless needed.

Question 30

Which of the following acts as a corepressor to block transcription of the trp operon?

A) cAMP
B) Lactose
C) Methionine
D) Tryptophan
E) CRP

Question 31

In the absence of substance M,a hypothetical LM operon is turned off.If substance M is abundant,it can bind to the repressor,which permits the polymerase to begin transcribing the DNA.In this case,LM is a(n)_______ operon and M acts as a(n)_______.

A) repressible;inducer
B) repressible;transcription factor
C) inducible;inducer
D) inducible;corepressor
E) inducible;transcription factor

Question 32

What is a likely advantage of transcriptional regulation over allosteric regulation?

A) In transcriptional regulation,only the final product is regulated;thus,it is more efficient.
B) In allosteric regulation,the continued production of enzymes is energetically costly.In transcriptional regulation,it is possible to shut down the production of the enzymes.
C) Allosteric regulation is necessarily slower than transcriptional regulation.
D) Allosteric regulation requires cofactors that are not required by transcriptional regulation.
E) Transcriptional regulation can be inducible or repressible.

Question 33

In eukaryotes,a promoter is the region of

A) a plasmid that binds the enzymes for replication.
B) the mRNA that binds to a ribosome.
C) the DNA that binds RNA polymerase.
D) the mRNA that binds tRNAs.
E) the DNA that binds DNA polymerase.

Question 34

Which statement about the early genes in the T4 bacteriophage is false?

A) They require RNA polymerase from the host bacterium in order to be transcribed.
B) Some of them stimulate the production of late genes.
C) At least one early gene produces the capsid proteins.
D) At least one early gene shuts down expression of the host genome.
E) They stimulate viral genome replication.

Question 35

In a repressible operon,the repressor molecule

A) can control the operon only after it is activated by a corepressor.
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 first be made negative to control the operon.

Question 36

Suppose that a certain enzyme is synthesized whenever the solution in which the cells are growing contains substance Y.When substance Y is not present,the enzyme is produced only under certain environmental conditions.This phenomenon would most likely be an example of _______ gene regulation.

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

Question 37

Suppose that a certain enzyme is synthesized whenever the solution in which the cells are growing lacks substance X.When substance X is present,the enzyme is produced only under certain environmental conditions.This phenomenon would most likely be an example of _______ gene regulation.

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

Question 38

How are inducible and repressible systems similar?

A) Both systems control primarily catabolic pathways.
B) In both systems,the final product of the pathway usually regulates transcription of the genes that will encode enzymes that produce it.
C) In both systems,the regulatory molecules function by binding to the operator.
D) Blocking transcription is the default state for both systems.
E) Both systems control primarily anabolic pathways.

Question 39

In what way does gene regulation differ in eukaryotes and prokaryotes?

A) The prokaryotic RNA polymerase can bind directly to DNA,whereas the eukaryotic polymerase cannot.
B) The eukaryotic RNA polymerase can bind directly to DNA,whereas the prokaryotic polymerase cannot.
C) Global gene regulation is absent in prokaryotes.
D) DNA-protein interactions are involved in gene regulation only in prokaryotes.
E) Sigma factors are absent in eukaryotes.

Question 40

If a virus is in the lysogenic phase,it will

A) integrate its DNA into the host cell chromosome.
B) excise its DNA from the host cell chromosome.
C) lyse or cut open the host cell.
D) induce point mutations in the host cell.
E) activate the host cell DNA.

Question 41

Transcription factors are

A) RNA sequences that bind to RNA polymerase.
B) proteins that bind to the DNA promoter sequence.
C) DNA sequences that regulate transcription.
D) polysaccharides that bind to the transcripts.
E) factors that bind to enhancers.

Question 42

In a 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 43

The HIV virus that causes AIDS is a(n)

A) arbovirus.
B) double-stranded DNA virus.
C) single-stranded DNA virus.
D) porcine virus.
E) retrovirus.

Question 44

The binding of TFIID to the promoter _______,thereby enabling the binding of other transcription factors.

A) methylates the DNA
B) demethylates the DNA
C) changes the shape of the DNA
D) produces signals that attract other transcription factors
E) blocks the RNA polymerase binding site

Question 45

What type of molecule is a transcription factor?

A) Protein
B) Enzyme
C) DNA
D) Carbohydrate
E) Lipid

Question 46

The binding of an enhancer

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

Question 47

In what way are HIV and T4 phage similar?

A) They are both retroviruses.
B) They both (at least initially)rely on the host RNA polymerase to transcribe their genes.
C) They both produce capsids.
D) They are both proviruses.
E) They can both replicate themselves outside a host cell.

Question 48

The TATA box is a(n)

A) activator sequence necessary for proper translation.
B) general transcription factor.
C) enhancer consensus sequence.
D) sequence close to the promoter region of many genes.
E) repressor sequence.

Question 49

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

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

Question 50

The drought stress response in plants is an example of

A) a transcription factor.
B) coordinated gene expression.
C) a strategy for increasing water intake.
D) a response resulting from a single transcription factor.
E) an inhibitory element.

Question 51

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 52

Many genes involved in the development of animal embryos have similar regulatory sequences.It is likely,therefore,that these

A) sequences bind the same groups of transcription factors.
B) genes are not regulated together.
C) genes have the dehydration response element (DRE).
D) genes are regulated by maternal effect transcription factors.
E) sequences code for homologous proteins.

Question 53

If a mutation in a silencer makes it much more difficult for it to be bound by proteins,what is most likely to occur?

A) A specific gene near the silencer will be transcribed all the time,even when it is 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 54

In eukaryotic cells,a negative regulator or silencer

A) is made of DNA.
B) binds to the enhancer region to block transcription.
C) is located both upstream and downstream from the promoter.
D) binds to the operator to block RNA polymerase.
E) binds to a repressor protein to reduce transcription rates.

Question 55

TFIID is

A) a promoter.
B) an enzyme.
C) part of the TATA box.
D) a promoter and a transcription factor.
E) a protein and a transcription factor.

Question 56

Transcription of eukaryotic genes requires the

A) binding of RNA polymerase to the promoter.
B) binding of only one transcription factor.
C) capping of mRNA.
D) addition of a poly-A tail to mRNA.
E) blocking of the TATA box by a repressor.

Question 57

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) Its binding to DNA changes the shape of the DNA.
D) It attracts other transcription factors to the transcription initiation complex.
E) It must bind RNA polymerase II before binding to the TATA box.

Question 58

What is the main difference between eukaryotic and prokaryotic gene regulation?

A) Groups of eukaryotic genes are likely to be regulated together,whereas each prokaryotic gene is usually regulated separately.
B) Groups of prokaryotic genes are likely to be regulated together,whereas each eukaryotic gene is usually regulated separately.
C) Prokaryotes have more classes of RNA polymerase than eukaryotes do.
D) Only prokaryotes have global gene regulation.
E) Only eukaryotes have global gene regulation.

Question 59

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 regulatory sequences more tightly than general transcription factors do.
D) Specific transcription factors bind to regulatory sequences of fewer genes than general transcription factors do.
E) Specific transcription factors bind regulatory sequences less tightly than general transcription factors do.

Question 60

In eukaryotic cells,a positive regulator or enhancer

A) binds to the enhancer region to block transcription.
B) is made of RNA.
C) binds to an activator protein to increase transcription rates.
D) is a carbohydrate.
E) is an enzyme.

Question 61

Two identical twins who showed very similar methylation patterns when they were 4 years old show very divergent patterns at age 40.This divergence is most likely due to

A) different genomic imprinting in the two individuals.
B) different alternative splicing in the two individuals.
C) environmental differences that they experienced as adults.
D) different levels of histone acetyltransferase in the two individuals.
E) differences in their experiences in utero.

Question 62

Without maintenance methylase,the changes made by DNA methylase would not

A) be able to decrease transcription of a gene.
B) be able to increase transcription of a gene.
C) be passed on from one generation to the next.
D) coordinate regulation across different genes.
E) produce microRNA.

Question 63

Which enzyme is involved in epigenetic changes?

A) DNA ligase
B) Maintenance methylase
C) Histone deacetylase
D) Maintenance deacetylase
E) DNA prophase

Question 64

Heterochromatin stains _______ than euchromatin and is _______ transcriptionally active.

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

Question 65

Genomic imprinting

A) marks the parental origin of alleles.
B) explains why euchromatin and heterochromatin are different.
C) explains differences in the epigenomes of adult monozgotic twins.
D) alters the DNA sequence.
E) is not found in mammals.

Question 66

Recent studies of monozygotic twins have revealed that

A) methylation patterns become more similar over time.
B) methylation patterns become less similar over time.
C) the environment does not have a large influence on the epigenome.
D) methylation patterns do not change over time.
E) methylation patterns have no effect on gene expression.

Question 67

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 68

The differences between the versions of the Sxl proteins found in male and female Drosophila are generated by the process of

A) methylation.
B) coordinate regulation.
C) alternative splicing.
D) induction.
E) demethylation.

Question 69

A virus-encoded protein called Tat is

A) a component of a cell's negative regulation against HIV.
B) a co-receptor that allows HIV to enter cells.
C) a protein used by HIV to evade host cell defenses.
D) a protein produced by HIV that interferes with transcription of host genes.
E) a protein used by host cells to promote HIV integration.

Question 70

If each interphase nucleus in a preparation of normal rat epithelial cells is found to contain a single Barr body,one can conclude that

A) the cells are in meiotic prophase.
B) all of the chromatin in these cells is inactive.
C) the DNA in these cells has replicated itself.
D) the cells are not transcribing any genes.
E) the cells came from a female rat.

Question 71

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 72

If an HIV lineage obtains a mutation that causes its Tat protein to be somewhat less able to bind to RNA,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 73

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) Epigenetic changes cannot be inherited.

Question 74

Human males with Kleinfelter's syndrome have two X chromosomes (they are XXY).One of the X chromosomes is usually silenced in a process similar to the process that inactivates one copy of X in each cell of XX females.Therefore,a Kleinfelter's male has _______ Barr body(ies),because _______.

A) no;Barr bodies do not form in males
B) one;the Barr body is the active X chromosome
C) one;the Barr body is the inactive X chromosome
D) two;these males have two X chromosomes
E) three;these males have three sex chromosomes

Question 75

The presence of a Barr body indicates

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

Question 76

In Drosophila and many other insects,the regions near the centromeres of most chromosomes are largely heterochromatin.These regions,therefore,are likely to be _______ methylated and to have _______ gene activity.

A) heavily;low to no
B) heavily;high
C) lightly;high
D) variably;high
E) lightly;low

Question 77

Which of the following is an example of an epigenetic change?

A) A mutation that changes adenine to guanine
B) Methylation of a cytosine
C) The binding of a transcription factor to a sequence of DNA
D) The mutation of an activator binding site
E) The mutation of a repressor binding site

Question 78

Nucleosomes disaggregate and reaggregate

A) through alternative splicing.
B) through the attachment of ubiquitin.
C) through the alternation of nucleotides.
D) by acetylation and deacetylation.
E) through the insertion of nucleotides.

Question 79

Alternative splicing helps to explain

A) the small number of genes in the human genome.
B) why there are more mRNAs than there are human genes.
C) the great variety in proteins.
D) why different proteins can be made from the same genes.
E) All of the above

Question 80

The activity of _______ tends to lead to increased transcription.

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