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Chapter 16: Regulation of Gene Expression

1. 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.
2. 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.
3. 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.
4. 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.
5. 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
6. 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
7. 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
8. 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
9. 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.
10. 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.
11. 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
12. 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.
13. The genetic information of viruses can be
a. DNA.
b. RNA.
c. single-stranded.
d. double-stranded.
e. All of the above
14. 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
15. 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.
16. 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.
17. The effects of Cro and cI on bacteriophage λ are
a. competitive.
b. cooperative.
c. coordinate.
d. inverted.
e. additive.
18. 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
19. 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.
20. 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. β-galactosidase is required for glucose metabolism.
e. three different proteins are synthesized when glucose is present.
21. 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. β-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.
22. 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.
23. 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
24. 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
25. The genes that encode repressor proteins are
a. repressor genes.
b. operons.
c. inducer genes.
d. regulatory genes.
e. None of the above
26. 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.
27. _______ acts as a co-repressor to block transcription of the tryptophan operon.
a. cAMP
b. Lactose
c. Tryptophan
d. Methionine
e. CRP
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
29. 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
30. 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
31. 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.
32. 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
33. 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
34. 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.
35. 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.
36. 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
37. 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
38. 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
39. 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
40. 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
41. 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.
42. 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.
43. 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
44. 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.
45. 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
46. 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
47. Which of the following is a transcription factor?
a. A regulatory protein
b. RNA
c. DNA
d. Carbohydrate
e. Enzyme
48. 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.
49. 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
50. The different members of the β-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.
51. 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.
52. 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
53. 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.
54. 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.
55. 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.
56. Which of the following statements about β-globin production is true?
a. A translational repressor protein binds to the β-globin and prevents ribosomes from attaching.
b. Alternative splicing of pre-mRNA results in the production of several different β-globins.
c. Transcription of the β-globin gene is determined by transcription factors, regulators, enhancers, activators, silencers, and repressors.
d. Ubiquitin forms a complex with the β-globin that causes its premature breakdown.
e. The 5´ guanosine cap added to the mRNA is the location where RNA polymerase initiates transcription.
57. 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
58. 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
59. 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.
60. 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.
61. 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.
62. 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.
63. 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.
64. 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.
65. 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.
66. 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
67. 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.
68. 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
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.
70. 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
71. One of the genes that is known to be transcribed from the inactive X chromosome is
a. Xist.
b. ZIST.
c. inactivation controller protein.
d. lithozist.
e. methyl-X.
72. Expression of some eukaryotic genes can be regulated by translational control. One advantage of translational control is that it
a. provides a means for rapid change in protein concentrations.
b. prevents synthesis of excess RNA.
c. directs proteins to their proper subcellular location.
d. occurs only in zygotes.
e. degrades proteins that are no longer needed.
73. Alternative splicing helps to explain
a. the small number of genes in the human genome.
b. the differences in complexity among organisms.
c. why there are more mRNAs than human genes.
d. the great variety in proteins.
e. All of the above
74. 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. catalytic RNA activity.
d. posttranscriptional control.
e. the endosymbiotic theory.
75. Which of the following is not a control mechanism for regulating the amount of protein synthesized in eukaryotic cells?
a. Transcription regulation
b. Inhibit translation with miRNAs
c. Transcript processing
d. Breakdown of the synthesized protein
e. Stabilization of the mRNA
76. Ubiquitin forms a complex with proteins and then binds with _______, forming a sort of "molecular chamber of doom," where proteins are digested into small peptides and amino acids.
a. the extracellular space
b. mitochondria
c. the proteasome
d. lysosomes
e. the Golgi apparatus
77. Some metabolic pathways are regulated in part by changes in the rate of degradation of key enzymes. This is an example of
a. operon control.
b. transcriptional control.
c. liquid hybridization.
d. feedback inhibition.
e. posttranslational control.