Deck 16: Regulation of Gene Expression

Question 1

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) exchange of genetic material between a bacteriophage and a bacterium.

Answer 1

A

Question 2

The promoter in the lac operon is

A) the region that binds the repressor.
B) the region that binds RNA polymerase.
C) the gene that codes for the repressor.
D) a structural gene.
E) an operon.

Answer 2

B

Question 3

In the lysogenic cycle of bacteriophage $\lambda$ ,

A) a repressor, cI, blocks the lytic cycle.
B) the bacteriophage carries DNA between bacterial cells.
C) both early and late phage genes are transcribed.
D) the viral genome is made into RNA, which stays in the host cell.
E) many new viruses are made immediately, regardless of host health.

Answer 3

a repressor, cI, blocks the lytic cycle.

Question 4

CREB is a transcription factor that regulates gene expression. It binds to DNA and activates promoters of genes involved in addictive behaviors in alcoholism. Researchers compared CREB levels in the brains of a strain of rats called P rats and wild-type rats. 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 5

In transduction,

A) only a particular part of the bacterial chromosome can be transferred.
B) a part of the bacterial chromosome may be transferred.
C) only the F plasmid can be transferred.
D) only the part of the bacterial chromosome near the F plasmid can be transferred.
E) None of the above

Question 6

Which of the following is true of both positive and negative gene regulation?

A) They reduce the rate of transcription of certain genes.
B) They involve regulatory proteins (or RNA) binding to DNA.
C) They involve transcription of all genes in the genome.
D) They are not both active in the same organism or virus.
E) They act away from the promoter.

Question 7

Which of the following is not a type of viral reproduction?

A) DNA virus in a lytic cycle
B) DNA virus in a lysogenic cycle
C) DNA virus (single-stranded) with a double-stranded DNA intermediate
D) RNA virus with reverse transcription to make cDNA
E) RNA virus acting as tRNA

Question 8

Which statement about selective gene transcription in eukaryotes is not true?

A) Regulatory proteins can bind at a site on DNA distant from the promoter.
B) Transcription requires transcription factors.
C) Genes are usually transcribed as groups called operons.
D) Both positive and negative regulation occur.
E) Many proteins bind at the promoter.

Question 9

Which of the following statements 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 readily destroyed by antibiotics.

Question 10

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 11

In DNA, 5-methylcytosine

A) forms a base pair with adenine.
B) is not recognized by DNA polymerase.
C) is related to transcriptional silencing of genes.
D) does not occur at promoters.
E) is an irreversible modification of cytosine.

Question 12

Which of the following statements about the lytic cycle is true?

A) The phage DNA integrates into the bacterial chromosome.
B) Temperate viruses are formed.
C) Prophages are replicated.
D) The host cell lyses.
E) Immunity to a specific strain of phage may result.

Question 13

Beginning with a single bacterium, how many cells would be present after 4 hours of growth if they can double every 20 minutes?

A) 12
B) 24
C) 64
D) 4,096
E) 34,217,728

Question 14

Epigenetic changes

A) can involve DNA methylation.
B) are due to nonhistone protein acetylation.
C) are due to changes in the genetic code.
D) are an example of positive control of translation.
E) are never reversible.

Question 15

Viruses are composed of

A) nucleic acids only.
B) proteins only.
C) nucleic acids and proteins.
D) nucleic acids, proteins, and organelles.
E) nucleic acids and proteins, although a few also have organelles.

Question 16

Control of gene expression in eukaryotes includes all of the following except

A) alternative RNA splicing.
B) binding of proteins to DNA.
C) transcription factors.
D) stabilization of mRNA by miRNA.
E) DNA methylation.

Question 17

Which of the following statements about the lac operon is not true?

A) When lactose binds to the repressor, the repressor can no longer bind to the operator.
B) When lactose binds to the operator, transcription is stimulated.
C) When the repressor binds to the operator, transcription is inhibited.
D) When lactose binds to the repressor, the shape of the repressor is changed.
E) The repressor has binding sites for both DNA and lactose.

Question 18

An operon is

A) a molecule that can turn genes on and off.
B) an inducer bound to a repressor.
C) a series of regulatory sequences controlling transcription of protein-coding genes.
D) any long sequence of DNA.
E) a promoter, an operator, and a group of linked structural genes.

Question 19

The transfer of genes by a bacteriophage vector characterizes which type of gene transfer in bacteria?

A) Transformation
B) Conjugation
C) Transduction
D) Transference
E) None of the above

Question 20

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.
E) None of the above

Question 21

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.
E) All of the above

Question 22

_______ acts as a co-repressor to block transcription of the tryptophan operon.

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

Question 23

When E. coli are grown in a medium with low levels of lactose,

A) all the enzymes of the lactose operon are present in very small quantities.
B) all the enzymes of the lactose operon are present in large quantities.
C) no enzymes of the lactose operon are present.
D) $\beta$ -galactosidase and permease are present in small quantities, but transacetylase is present in large quantities.
E) the mRNA of the lactose operon is not present at all.

Question 24

The determination of whether a temperate phage undergoes a lytic or a lysogenic cycle depends on the

A) presence or absence of protein CD4.
B) two viral regulatory proteins, cI and Cro.
C) presence or absence of plasmodesmata.
D) nucleotide sequences of the phage.
E) size of the genome.

Question 25

The three basic parts of an operon are the

A) promoter, the operator, and two or more structural genes.
B) promoter, the structural genes, and the termination codons.
C) promoter, the mRNA, and the termination codons.
D) structural genes, the mRNA, and the tRNAs.
E) None of the above

Question 26

The influenza virus and the HIV virus differ in that only the influenza virus can

A) produce and use reverse transcriptase.
B) use RNA as its genetic material.
C) use RNA as genetic information and mRNA without generating a DNA molecule.
D) infect both horses and humans.
E) All of the above

Question 27

The retrovirus HIV enters a host cell

A) by fusion of its envelope with the host's plasma membrane.
B) by endocytosis.
C) by vectors.
D) through cytoplasmic connections between cells (plasmodesmata).
E) by phagocytosis.

Question 28

It is found that a certain enzyme is synthesized whenever the solution in which the cells are growing lacks substance X. This phenomenon is most likely an example of _______ gene regulation.

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

Question 29

Lysis of the host cell is caused by

A) the cell's bursting due to the large number of viral particles.
B) the cell's opening up in an attempt to release the viruses.
C) an attack on the cell wall by a product of the viral gene.
D) an as yet unknown mechanism.
E) None of the above

Question 30

It is found that a certain enzyme is synthesized whenever the solution in which the cells are growing contains substance X. This phenomenon is most likely an example of _______ gene regulation.

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

Question 31

A prokaryotic cell can control the amount of enzymes it produces by

A) blocking transcription.
B) hydrolyzing the mRNA after it is made.
C) preventing translation of mRNA.
D) hydrolyzing the protein after translation.
E) All of the above

Question 32

An inducer

A) inhibits the synthesis of the needed enzyme(s).
B) stimulates the synthesis of the 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 33

Research on E. coli indicates that

A) lactose is the preferred energy source.
B) glucose is the preferred energy source.
C) lactose and glucose are used equally as an energy source.
D) $\beta$ -galactosidase is required for glucose metabolism.
E) three different proteins are synthesized when glucose is present.

Question 34

The most efficient means of regulating protein synthesis 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 35

In a repressible operon, the repressor molecule

A) must first be activated by a co-repressor.
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

The lac operon of E. coli consists of

A) a segment of DNA.
B) a promoter.
C) an operator.
D) three structural genes.
E) All of the above

Question 37

The effects of Cro and cI on bacteriophage $\lambda$ are

A) competitive.
B) cooperative.
C) coordinate.
D) inverted.
E) additive.

Question 38

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 39

The genetic information of viruses can be

A) DNA.
B) RNA.
C) single-stranded.
D) double-stranded.
E) All of the above

Question 40

The genes that encode repressor proteins are

A) repressor genes.
B) operons.
C) inducer genes.
D) regulatory genes.
E) None of the above

Question 41

Which of the following statements about TATA boxes is false?

A) They bind a specific transcription factor.
B) They are found in the region of the promoter.
C) They are part of the intron consensus sequence.
D) They help specify the starting point for transcription.
E) They contain thymine-adenine base pairs.

Question 42

Gene expression can be regulated

A) before transcription.
B) during transcription and before translation.
C) during translation.
D) after translation.
E) All of the above

Question 43

The TATA box is a(n)

A) sequence close to the promoter region of many genes.
B) square-shaped sequence.
C) enhancer consensus sequence.
D) activator sequence necessary for proper translation.
E) None of the above

Question 44

In eukaryotic cells, promoters are

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

Question 45

A promoter is the region of

A) a plasmid that binds the enzymes for replication.
B) the mRNA that binds to a ribosome.
C) DNA that binds RNA polymerase.
D) the mRNA that binds tRNAs.
E) None of the above

Question 46

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 47

A DNA sequence, which can be distant from the gene, stimulates transcription when bound by a protein. This sequence is called a(n)

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

Question 48

How are inducible and repressible systems similar?

A) They both control catabolic pathways.
B) They both control biosynthetic pathways.
C) In both systems the regulatory molecules function by binding to the operator.
D) They both block transcription.
E) Both systems are unique to prokaryotes.

Question 49

Which operon is turned "off" in response to molecules present in the environment of the cell?

A) Repressible
B) Suppressible
C) Impressible
D) Inducible
E) Degraded

Question 50

When the concentration of glucose is high, the concentration of _______ is low.

A) CRP
B) cAMP
C) repressors
D) inducers
E) None of the above

Question 51

There are several proteins involved in transcription, including transcription factors, regulatory binding proteins, and activators. Their role is to tell RNA polymerase

A) where to start transcribing the DNA.
B) which genes to transcribe.
C) where to stop transcribing the DNA.
D) Both a and b
E) a, b, and c

Question 52

When the operator is unbound, the binding of the CRP-cAMP complex _______ the binding of RNA polymerase at the promoter.

A) prevents
B) decreases
C) increases
D) blocks
E) All of the above are sometimes true, depending on the concentration of lactose.

Question 53

RNA polymerase II by itself cannot bind to the chromosome and initiate transcription. It can bind and act only after regulatory proteins called _______ factors have been assembled.

A) translation
B) posttranslation
C) initiation
D) transcription
E) None of the above

Question 54

Catabolite repression refers to the

A) increased transcription from many operons when glucose is present in the medium.
B) shutdown of transcription from many operons when glucose is present in the medium.
C) increased activity of inducers caused by glucose in the medium.
D) Both a and b
E) Both a and c

Question 55

What effect does the presence of ample glucose have on the amount of lac operon transcription?

A) It increases the cAMP concentration, which in turn causes a decreased rate of transcription.
B) It decreases the cAMP concentration, which in turn causes an increased rate of transcription.
C) It increases the rate of transcription.
D) It decreases the rate of transcription.
E) None of the above

Question 56

Which of the following is a transcription factor?

A) A regulatory protein
B) RNA
C) DNA
D) Carbohydrate
E) Enzyme

Question 57

Transcription of eukaryotic genes requires

A) binding of RNA polymerase to the promoter.
B) binding of several transcription factors.
C) capping of mRNA.
D) Both a and b
E) All of the above

Question 58

The different members of the $\beta$ -globin gene family

A) are expressed differently in different tissues.
B) are expressed differently at different times of development.
C) are expressed in the same way in different tissues.
D) are expressed in the same way at different times of development.
E) have no known function.

Question 59

The CRP-cAMP complex binds _______ of the operon.

A) close to the RNA polymerase binding site
B) close to the operator
C) inside one of the structural genes
D) at the termination point
E) None of the above

Question 60

Transcription factors are

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

Question 61

DNA is wound around histones to form structures that block both the initiation and elongation steps of transcription. These structures are

A) condensed chromosomes.
B) lampbrush chromosomes.
C) nucleosomes.
D) the solenoid structure of DNA.
E) 30 nm DNA fibers.

Question 62

The Barr body is evidence for

A) X chromosome inactivation.
B) cell death.
C) ion pumps.
D) posttranslational control of eukaryotic gene expression.
E) None of the above

Question 63

Several types of histone modification affect gene activation and repression. Cancer cells are characterized by a greater degree of

A) methylation.
B) phosphorylation.
C) acetylation.
D) interference.
E) deacetylation.

Question 64

A chemical modification that adds methyl groups to cytosine residues in some genes acts to

A) enhance transcription.
B) amplify the gene.
C) inactivate the gene.
D) stabilize the mRNA.
E) None of the above

Question 65

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 66

Mary Lyon, Liane Russell, and Ernest Beutler discovered

A) the basis of hormone action.
B) X chromosome inactivation.
C) Barr bodies.
D) melanosomes.
E) heterochromatin.

Question 67

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 68

Nucleosomes disaggregate to allow transcription and then reaggregate

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

Question 69

Heterochromatin

A) contains poly A tails.
B) is rarely transcribed.
C) does not contain any DNA.
D) is not replicated during the S phase.
E) is found only in prokaryotes.

Question 70

A cell that contains three Barr bodies will necessarily have

A) three Y chromosomes.
B) three X chromosomes.
C) four Y chromosomes.
D) four X chromosomes.
E) three nucleoli.

Question 71

The interphase cells of normal female mammals have a stainable nuclear body called a Barr body. This body is

A) an inactive X chromosome.
B) made of fat droplets.
C) made of fragments of mRNA.
D) made of extra chromosomal pieces.
E) None of the above

Question 72

Which of the following statements about $\beta$ -globin production is true?

A) A translational repressor protein binds to the $\beta$ -globin and prevents ribosomes from attaching.
B) Alternative splicing of pre-mRNA results in the production of several different $\beta$ -globins.
C) Transcription of the $\beta$ -globin gene is determined by transcription factors, regulators, enhancers, activators, silencers, and repressors.
D) Ubiquitin forms a complex with the $\beta$ -globin that causes its premature breakdown.
E) The 5´ guanosine cap added to the mRNA is the location where RNA polymerase initiates transcription.

Question 73

Which of the following statements about the globin genes is true?

A) Different genes are expressed during different stages of prenatal development.
B) Only one copy is functional.
C) The lengths of the mRNAs are very different for different genes.
D) They are the result of differential posttranscriptional splicing.
E) The transcripts are longer than the coding regions.

Question 74

In neurons, the globin gene contains many methylated cytosines. The globin gene, therefore, is

A) expressed only in males.
B) expressed only in females.
C) not expressed.
D) regulated by posttranscriptional control.
E) regulated by posttranslational control.

Question 75

DNA methylation in eukaryotic chromosomes involves adding a methyl to the

A) 5´ position of G.
B) 5´ position of C.
C) proteins bound to the DNA.
D) RNA molecules.
E) ribose.

Question 76

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 all genes.
D) stimulates splicing of a specific mRNA.
E) stimulates splicing of all mRNAs.

Question 77

DNA methylation

A) is a mechanism of gene inactivation.
B) adds methyl groups to cytosine residues in certain genes.
C) inhibits transcription.
D) Both a and b
E) All of the above

Question 78

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.
D) the cells are not transcribing any genes.
E) the cells came from a female rat.

Question 79

Which of the following is not a DNA binding motif?

A) Helix-straight-helix
B) Helix-turn-helix
C) Helix-loop-helix
D) Leucine zipper
E) Zinc finger

Question 80

The drought stress response in plants is an example of

A) a transcription factor.
B) coordinated gene expression.
C) a way to increase water intake.
D) Both a and b
E) None of the above