OpenStax Microbiology Test Bank Chapter 11: Mechanisms of Microbial Genetics | LATEST UPDATE

OpenStax Microbiology Test Bank Chapter 11: Mechanisms of Microbial Genetics Chapter 11: Mechanisms of Microbial Genetics * = Correct answer Multiple Choice 1. Gene expression includes which of the following? A. DNA replication B. replication, transcription, and translation C. transcription and translation* D. translation only Difficulty: Easy ASM Standard: N/A 2. The central dogma describes which of the following? A. the process by which enzymes are modified after translation B. the steps of gene expression* C. the way DNA is replicated D. the way RNA is used as a template to make DNA Difficulty: Easy ASM Standard: N/A 3. During bacterial DNA replication, which of the following holds open the replication bubble? A. DNA polymerases B. helicases C. primers D. single-strand binding proteins* Difficulty: Easy ASM Standard: N/A 4. Telomeres found in which of the following? A. all microbes B. animal cells only, not in unicellular organisms C. fungal, protist, plant, and animal chromosomes* D. microbes only, including all domains Difficulty: Easy ASM Standard: 16 5. Which of the following best describes the direction in which lagging strands are added? A. as 5′ to 3′ Okazaki fragments in an overall 3′ to 5′ direction only* B. as 5′ to 3′ Okazaki fragments in an overall 5′ to 3′ direction only C. in the 3′ to 5′ or 5′ to 3′ direction Page 1 of 17 OpenStax Microbiology Test Bank Chapter 11: Mechanisms of Microbial Genetics D. in variable directions depending on the species Difficulty: Easy ASM Standard: N/A 6. Which of the following correctly describes uracil and where is it found? A. It is a nitrogenous base found in DNA and RNA. B. It is a nitrogenous base found in DNA only. C. It is a nitrogenous base found in RNA only.* D. It is a nitrogenous base found only in nucleotides of molecules other than RNA and DNA. Difficulty: Easy ASM Standard: N/A 7. Which of the following is another name for the template strand (the strand of DNA that is transcribed)? A. anticodon strand B. antisense strand* C. sense strand D. transcription strand Difficulty: Moderate ASM Standard: N/A 8. Which of the following correctly describes events that occur during transcription? A. DNA polymerase binds to the site of initiation. B. RNA polymerase binds to the core enzyme. C. RNA polymerase binds to the operator. D. RNA polymerase binds to the promoter.* Difficulty: Easy ASM Standard: N/A 9. Which of the following correctly explains why DNA replication is described as semiconservative? A. Each daughter strand contains one old strand and one new strand.* B. Each daughter strand contains two new strands. C. The nucleotides used in replication are recycled multiple times. D. The nucleotides used in replication contain old and new components. Difficulty: Moderate ASM Standard: N/A 10. During DNA replication in bacteria, which of the following enzymes adds DNA nucleotides to the growing strand? A. DNA polymerase I Page 2 of 17 OpenStax Microbiology Test Bank Chapter 11: Mechanisms of Microbial Genetics B. DNA polymerase II C. DNA polymerase III* D. DNA polymerase IV Difficulty: Moderate ASM Standard: 16 11. Topoisomerase II in bacteria is also called which of the following? A. gyrase* B. helicase C. primase D. topoisomerase β Difficulty: Moderate ASM Standard: 16 12. DNA polymerase III adds DNA nucleotides in which of the following direction(s)? A. in the 3′ to 5′ direction only B. in the 3′ to 5′ direction and in 5′ to 3′ direction C. in the 5′ to 3′ direction on one strand and in the 3′ to 5′ direction on the complementary strand D. in the 5′ to 3′ direction only* Difficulty: Moderate ASM Standard: 16 13. Which of the following removes the primers during DNA replication in bacteria? A. DNA polymerase I* B. DNA polymerase II C. DNA polymerase III D. DNA polymerase IV Difficulty: Moderate ASM Standard: 16 14. The noncoding, repetitive sequences at the end of eukaryotic chromosomes are called which of the following? A. bubbles B. forks C. lagging strands D. telomeres* Difficulty: Easy ASM Standard: 16 15. During DNA replication, the lagging strand is formed from which of the following? Page 3 of 17 OpenStax Microbiology Test Bank Chapter 11: Mechanisms of Microbial Genetics A. helicases B. leading strands C. Okazaki fragments* D. single strand binding proteins Difficulty: Moderate ASM Standard: N/A 16. Which of the following is the maximal rate of growth of a new bacterial DNA strand? A. 10 nucleotides per second B. 100 nucleotides per second C. 1000 nucleotides per second* D. 10,000 nucleotides per second Difficulty: Moderate ASM Standard: N/A 17. Which statement best describes DNA polymerase I? A. It acts as a ligase. B. It has exonuclease activity.* C. It joins fragments together. D. It prevents supercoiling. Difficulty: Moderate ASM Standard: 16 18. Which describes one difference between prokaryotic and eukaryotic DNA replication? A. Eukaryotes have more origins of replication than prokaryotes.* B. The chromosomes are usually circular in eukaryotes and usually linear in prokaryotes. C. The DNA is not tightly complexed with histones in eukaryotes. D. The RNA primer is removed by ribonuclease H instead of a DNA polymerase I in prokaryotes Difficulty: Moderate ASM Standard: 16 19. Telomerase in humans is generally active in which cells? A. all cells B. all cells during childhood, but not during adulthood C. in stem cells and germ cells* D. stem cells only Difficulty: Moderate ASM Standard: N/A 20. Which of the following uses rolling circle replication? Page 4 of 17 OpenStax Microbiology Test Bank Chapter 11: Mechanisms of Microbial Genetics A. some bacteria only B. some bacteria and some viruses C. some bacteria, some plasmids, and some viruses* D. some bacteria, some plasmids, some viruses, and some eukaryotic main chromosomes Difficulty: Moderate ASM Standard: 16 21. Which of the following defines a sigma () factor? A. a subunit of eukaryotic RNA polymerase that is important in binding to DNA B. a subunit of eukaryotic RNA polymerase that is important in binding to RNA B. a subunit of prokaryotic RNA polymerase that is important in binding to DNA* C. a subunit of prokaryotic RNA polymerase that is important in binding to RNA Difficulty: Easy ASM Standard: 16 22. Which sequences of eukaryotic genes code for proteins? A. exons* B. introns C. invariant D. the spliceosome Difficulty: Moderate ASM Standard: 16 23. Which of the following is one important distinction between prokaryotic and eukaryotic mRNA? A. Eukaryotic mRNA is generally monocistronic.* B. Eukaryotic mRNA is generally polycistronic. C. Eukaryotic mRNA is equally likely to be monocistronic or polycistronic. D. Eukaryotic mRNA is often both monocistronic and polycistronic within an operon. Difficulty: Moderate ASM Standard: 16 24. Stop codons are also known as which of the following? A. antisense codons B. missense codons C. nonsense codons* D. sense codons Difficulty: Moderate ASM Standard: N/A 25. Which researchers provided evidence that DNA replication was semiconservative? Page 5 of 17 OpenStax Microbiology Test Bank Chapter 11: Mechanisms of Microbial Genetics A. George Beadle, Edward Tatum, and colleagues B. Alfred Hershey and Martha Chase C. Matthew Meselson and Franklin Stahl* D. James Watson and Francis Crick Difficulty: Moderate ASM Standard: N/A 26. Quinolones are medications that target which of the following? A. DNA gyrase and topoisomerase IV* B. ligase and topoisomerase III C. primase and topoisomerase I D. replicase and topoisomerase V Difficulty: Difficult ASM Standard: 14 27. Following DNA replication, bacterial chromosomes become which of the following? A. concatenated* B. linear C. plasmids D. single stranded Difficulty: Difficult ASM Standard: 16 28. Human telomeres contain 100 to 1000 copies of which nucleotide sequence? A. AATAT B. TATATA C. TTAGGG* D. TTTTTT Difficulty: Difficult ASM Standard: N/A 29. Which enzyme(s) elongate the lagging strand during replication in eukaryotes? A. DNA polymerases I and III B. DNA polymerase III C. DNA polymerase δ* D. DNA polymerase ε Difficulty: Difficult ASM Standard: 16 30. What does the σ factor recognize? Page 6 of 17 OpenStax Microbiology Test Bank Chapter 11: Mechanisms of Microbial Genetics A. the –10 consensus sequence in eukaryotes B. the –10 consensus sequence in prokaryotes C. the –35 consensus sequence in prokaryotes* D. the TATA box in eukaryotes Difficulty: Difficult ASM Standard: 16 31. Which of the following is the function of the σ factor? A. It allows DNA polymerase to recognize a specific promoter in eukaryotes. B. It allows RNA polymerase to bind to a specific promoter in eukaryotes. C. It allows RNA polymerase to recognize a specific promoter in prokaryotes.* D. It allows RNA polymerase to terminate transcription in prokaryotes. Difficulty: Difficult ASM Standard: 16 32. Which statement best describes selenocysteine and pyrrolysine? A. They are amino acids commonly found in eukaryotic proteins. B. They are amino acids commonly found in proteins in all microbes. C. They are unusual amino acids found in some archaea. D. They are unusual amino acids found in some bacteria and archaea.* Difficulty: Difficult ASM Standard: 16 33. Which statement best describes polyribosomes? A. They are only found in archaea. B. They can occur in archaea, bacteria, and eukaryotes during transcription. C. They can only form after RNA has left the nucleus in eukaryotes, but are found in all domains.* D. They can only form in eukaryotes, not in other organisms, and can only form once the RNA has been fully processed. Difficulty: Difficult ASM Standard: 16 34. Which amino acid is attached to a tRNA? A. aminoacyl tRNA synthetase B. an activated amino acid C. a charged amino acid D. a cognate amino acid* Difficulty: Difficult ASM Standard: N/A Page 7 of 17 OpenStax Microbiology Test Bank Chapter 11: Mechanisms of Microbial Genetics True/False 35. A particular genotype always produces the same phenotype. Answer: False Difficulty: Moderate ASM Standard: N/A 36. Prokaryotes usually have a single origin of replication, whereas eukaryotes usually have multiple origins of replication. Answer: True Difficulty: Easy ASM Standard: 16 37. Archaea, Bacteria, and Eukarya use different DNA polymerases. Answer: True Difficulty: Moderate ASM Standard: 16 38. RNA primases require a free 3′-OH group to add nucleotides to a growing strand. Answer: False Difficulty: Moderate ASM Standard: N/A 39. The termination of DNA replication is understood far better than the initiation of DNA replication. Answer: False Difficulty: Moderate ASM Standard: N/A 40. At 100 nucleotides per second, replication of eukaryotic DNA is faster than replication of prokaryotic DNA. Answer: False Difficulty: Moderate ASM Standard: 16 41. Prokaryotic RNA transcripts undergo splicing. Answer: False Difficulty: Difficult ASM Standard: 16 Page 8 of 17 OpenStax Microbiology Test Bank Chapter 11: Mechanisms of Microbial Genetics 42. Matthew Meselson and Franklin Stahl used radiolabeled phosphorus to determine that DNA replication is semiconservative. Answer: False Difficulty: Difficult ASM Standard: N/A Matching 43. Match each molecule with its function. A. mRNA i. brings in amino acids during translation. B. rRNA ii. carries encoded information from DNA C. tRNA iii. contributes to ribosome structure Answers: A. ii., B. iii., C. i. Difficulty: Easy ASM Standard: N/A 44. Match each molecule with its role in prokaryotic DNA replication. A. helicase i. helps hold open the double helix by preventing hydrogen bonding between the separated strands of the replication bubble B. ligase ii. helps hold DNA polymerase III in the proper position C. primase iii. synthesizes small pieces of RNA to start the synthesis of new DNA strands D. single-strand binding proteins iv. breaks hydrogen bonds between bases to open the double helix E. sliding clamp v. joins Okazaki fragments together Answers: A. iv., B. v., C. iii., D. i., E. ii. Difficulty: Moderate ASM Standard: 16 45. Match the enzyme with its role in prokaryotic DNA replication. A. DNA polymerase I i. relaxes supercoils and relieves stress on DNA B. DNA polymerase III ii. an exonuclease that removes RNA primers C. topoisomerase II iii. adds nucleotides in the 5′ to 3′ direction to produce the new complementary strand of DNA during replication D. topoisomerase IV iv. cuts DNA to release concatenated chromosomes and reseals the DNA Answers: A. ii., B. iii., C. i., D. iv. Difficulty: Moderate ASM Standard: 16 Page 9 of 17 OpenStax Microbiology Test Bank Chapter 11: Mechanisms of Microbial Genetics 46. Match the process that contributes to prokaryotic genetic diversity with the best description. A. conjugation i. DNA is transferred through a pilus. B. transduction ii. DNA is picked up from the environment. C. transformation iii. DNA is transferred by a bacteriophage. D. transposition iv. DNA excises from one location and inserts in another. Answers: A. i., B. iii., C. ii., D. iv. Difficulty: Moderate ASM Standard: 2 47. Match each part of the operon with its best description. A. operator i. site where RNA polymerase binds B. promoter ii. site where a repressor can bind C. structural genes iii. code for proteins with related functions Answers: A. ii., B. i., C. iii. Difficulty: Easy ASM Standard: 17 48. Match each mutagen with its effect on DNA. A. 2-aminopurine i. strand breaks or conversion of GC to AT pairs B. ethidium bromide ii. conversion of GC pairs to AT pairs C. nitrous oxide iii. distortion of the double helix, leading to small insertions and deletions D. X-rays and γ rays iv. conversion of AT pairs to GC pairs Answers: A. iv., B. iii., C. ii., D. i. Difficulty: Difficult ASM Standard: 2 Fill in the Blank 49. ________ expression occurs when genes are continuously expressed. Answer: Constitutive Difficulty: Easy ASM Standard: 17 50. The structure formed by an mRNA with multiple attached ribosomes is called a(n) ________. Answer: polyribosome Difficulty: Easy ASM Standard: 16 51. ________ mRNA codes for multiple polypeptides. Answer: Polycistronic Page 10 of 17 OpenStax Microbiology Test Bank Chapter 11: Mechanisms of Microbial Genetics Difficulty: Moderate ASM Standard: N/A 52. The ________ subunit of prokaryotic RNA polymerase helps it bind to the –35 consensus sequence. Answer: sigma (σ) Difficulty: Moderate ASM Standard: 16 53. ________ are transcription factors that can bind to the regulatory region of an operon to increase transcription levels above basal levels. Answer: Activators Difficulty: Moderate ASM Standard: 17 54. The tryptophan operon is turned off when there is an excess of tryptophan, making it a(n) ________ operon. Answer: repressible Difficulty: Moderate ASM Standard: 17 55. When lactose is present but there is no ________, the CAP–cAMP complex binds to the regulatory region of the lac operon. Answer: glucose Difficulty: Moderate ASM Standard: 17 56. ________ are nucleotide derivatives that change gene expression in response to stress and are especially important in pathogenic bacteria. Answer: Alarmones Difficulty: Moderate ASM Standard: 23 57. A molecule that influences regulation of prokaryotic gene expression found in the 5′ end of mRNA is called a(n) ________. Answer: riboswitch Difficulty: Difficult ASM Standard: 17 Page 11 of 17 OpenStax Microbiology Test Bank Chapter 11: Mechanisms of Microbial Genetics 58. The trp operon in Escherichia coli can be regulated by the type of stem loop structures formed, which is a type of regulation called ________? Answer: attenuation Difficulty: Difficult ASM Standard: 17 Short Answer 59. What is the term for horizontal gene transmission by a virus? Sample Answer: The term for horizontal gene transmission by a virus is transduction. Difficulty: Easy ASM Standard: 2 60. What is a riboswitch? Sample Answer: A riboswitch is found in the 5′ end of prokaryotic mRNA and regulates transcription and translation. Difficulty: Easy ASM Standard: 17 61. What is the term for the process by which mRNA is used to make a protein? Sample Answer: The process by which mRNA is used to make a protein is called translation. Difficulty: Easy ASM Standard: N/A 62. What is another term for the genetic elements often called “jumping genes?” Sample Answer: Jumping genes are also known as transposons. Difficulty: Easy ASM Standard: 2 63. Why is a primase required for DNA replication, instead of just using DNA polymerase? Sample Answer: DNA polymerase cannot add to free 3′-OH groups, but primase can. Difficulty: Moderate ASM Standard: 23, 24 64. Will the structural genes of the lac operon be expressed when there is plenty of lactose and glucose? Will the repressor be bound to the operator? Why or why not? Sample Answer: The repressor will not be bound to the operator because of the presence of lactose, but the high concentration of glucose will mean that there is only a low level of CAP–cAMP complex bound in the regulatory region. The structural genes will only be expressed at low levels. Page 12 of 17 OpenStax Microbiology Test Bank Chapter 11: Mechanisms of Microbial Genetics Difficulty: Moderate ASM Standard: 17 65. What is epigenetic regulation? Sample Answer: Epigenetic regulation is a type of regulation that occurs when DNA is modified in a way that does not affect the nucleotide sequence. This is often accomplished by methylation. Difficulty: Moderate ASM Standard: 17 66. Explain what a frameshift mutation is and why frameshift mutations often have severe consequences. Sample Answer: Frameshift mutations involve the addition or deletion of one or two bases and, therefore, cause a shift in the reading frame, meaning that all of the codons downstream are affected. These can potentially affect large parts of a protein and have very severe effects. Difficulty: Moderate ASM Standard: 2 67. What can cause a thymine dimer and what are the consequences of one forming? Sample Answer: Thymine dimers often result from nonionizing radiation exposure, such as exposure of the skin to UV radiation. The radiation causes two adjacent thymines to form a covalent link, forming a dimer. The dimer causes DNA replication and transcription to stall at its location. Replication will then proceed either with a point mutation or a frameshift mutation. Difficulty: Moderate ASM Standard: 2 68. How does horizontal gene transfer differ from vertical gene transfer? Sample Answer: Vertical gene transfer involves the transfer of genes from parents to offspring. When organisms exchange genes, it is called horizontal gene transfer. Horizontal gene transfer can take place through a variety of mechanisms and even between species that are not closely related. Difficulty: Moderate ASM Standard: 2 69. Why is the error rate for bacterial DNA replication very low? Sample Answer: Some forms of DNA polymerase are capable of proofreading. Difficulty: Moderate ASM Standard: 2 Page 13 of 17 OpenStax Microbiology Test Bank Chapter 11: Mechanisms of Microbial Genetics 70. How many of the 64 codons are stop codons? Sample Answer: There are three stop codons. Difficulty: Moderate ASM Standard: N/A 71. What does it mean to say that the genetic code is degenerate? Sample Answer: The genetic code is degenerate because there is more than one codon for most of the amino acids. Difficulty: Difficult ASM Standard: N/A 72. In eukaryotes, RNA produced by transcription is not immediately ready for translation. What steps have to take place before translation can occur? Sample Answer: For translation to occur, a 5′ cap and a polyA tail must be added. Next, RNA splicing takes place. Finally, the transcript must move from the nucleus to the cytoplasm because transcription takes place in the nucleus and translation takes place in the cytoplasm. Difficulty: Difficult ASM Standard: 16 73. What chemical reaction is catalyzed by DNA ligase? Sample Answer: DNA ligase joins fragments of DNA together during DNA replication. This is accomplished by forming phosphodiester linkages between the 5′ phosphate end of one fragment and the 3′-OH end of the other fragment. Difficulty: Difficult ASM Standard: N/A Brief Essay Essay Question Rubric RATING Failing Below Average Competent Advanced Criteria for evaluati on Answer does not provide an argument. Answer contains inaccuracies. Writing is poor and contains numerous grammatical mistakes and Answer fails to provide examples to support an argument. Writing is poor and grammatical errors are common. Answer is somewhat Answer provides an argument with one or two examples that support it. Writing is acceptable for the college level but may contain one or two Answer clearly provides an argument with two or more excellent examples that support it; student makes the argument clearly and eloquently. Answer is well Page 14 of 17 OpenStax Microbiology Test Bank Chapter 11: Mechanisms of Microbial Genetics misspellings. incoherent. grammatical mistakes or misspellings. organized and free of grammatical errors and misspellings. POINT VALUE 0 1 2 3 Assume rating/grading scale for the question ranges from 0 to 3 points. 74. Describe one way in which a transposon could cause a mutation. Be sure also to explain how transposons work. Answer: Student answers will vary but should include components of the following. Transposons produce transposase and are able to move from one location to another, sometimes by producing a copy and sometimes by simply moving. If they insert into another gene, they can inactivate it. Alternatively, they could insert a promoter and activate a gene that had previously been turned off. The term mutation describes any change in DNA that can be inherited, so this is a type of mutation. Difficulty: Moderate ASM Standard: 2 75. A transposon inserts structural genes (the genes that code for proteins) into the lac operon. What would happen if the bacterium were inoculated onto medium containing lactose? Explain what would happen by describing how each part of the operon would be affected (i.e., whether it would or would not be affected) and then whether the bacterium would metabolize lactose. Answer: Student answers will vary but should include components of the following. When the transposon inserts into a gene, the gene is likely to be mutated. The product probably will not be produced normally. In this case, one of the structural genes would be affected and the bacterium would not be able to produce all the proteins needed to metabolize lactose. The repressor would not bind to the operator because of the presence of lactose. RNA polymerase would bind to the promoter and begin transcription. However, one or more of the proteins probably would not be produced properly during translation and, therefore, the bacterium probably could not metabolize lactose. Difficulty: Moderate ASM Standard: 2 76. Ethidium bromide is commonly used to stain DNA on electrophoresis gels. However, ethidium bromide is a mutagen. Explain how ethidium bromide causes mutations in DNA. Answer: Student answers will vary but should include the following. Ethidium bromide is an intercalating agent, meaning that it inserts between DNA nucleotides. This distorts the double helix and can easily lead to insertions and deletions during DNA replication, because the bases are not paired up properly. Deletions and insertions of one or two bases can have severe consequences if they cause frameshift mutations, because all the codons downstream Page 15 of 17 OpenStax Microbiology Test Bank Chapter 11: Mechanisms of Microbial Genetics of the mutations will likely be incorrect, resulting in an incorrect sequence of amino acids in the translated polypeptide. Difficulty: Moderate ASM Standard: 2 77. Why is it necessary to have a control group when you use an Ames test? Answer: Student answers will vary but should include the following. The Ames test examines whether a particular chemical or other treatment causes mutations. Because mutations can occur spontaneously, it is important to have a control group so you can compare whether mutations increased in the treatment group (i.e., the bacteria exposed to the chemical of interest). If you just look for mutations, they will be present, to some extent, even if the chemical is not mutagenic. Difficulty: Moderate ASM Standard: 2 78. Explain the major differences in gene expression between prokaryotes and eukaryotes. Include at least three differences. Answer: Student answers will vary but should include components of the following and at least three of the examples given. Transcription and translation can occur simultaneously in prokaryotes, but the two processes occur separately in eukaryotes. In eukaryotes, RNA must be processed through the addition of a methyl cap, poly A tail, and splicing before translation. Additionally, the RNA must be transported from the nucleus to the cytoplasm before it can be translated. Ribosome structure differs in prokaryotes and eukaryotes as well. Prokaryotes have a 70S ribosome with a 30S subunit and a 50S subunit, whereas eukaryotes have an 80S ribosome with a 40S subunit and a 60S subunit. The first amino acid brought to the ribosome during translation is fMet in prokaryotes and Met in eukaryotes. Finally, the Shine-Dalgarno sequence is present in prokaryotes but not in eukaryotes. Additional differences (e.g., consensus sequences in DNA) also exist. (See Figures 11.16 and Table 11.17.) Difficulty: Difficult ASM Standard: 16 79. Mutations may be harmful but may also be beneficial or neutral. Explain some examples of neutral and beneficial mutations. Answer: Student answers will vary but should include components of the following. Neutral mutations have no effect on fitness (i.e., the ability of an organism to reproduce). They are not harmful or helpful. If the mutation occurs in the third base of a codon, the amino acid may not be changed (a silent mutation). Even if a single amino acid is changed, the protein may still function in some cases. Additionally, mutations may occur in noncoding regions and be neutral. Beneficial mutations may give an organism a new ability, such as antibiotic resistance. The text describes how a mutation may help to protect against HIV in the Micro Connections box “A Beneficial Mutation.” In this case, a mutation in the gene for a receptor causes an abnormal receptor to be produced and this interferes with the ability of HIV to bind to the cell. Page 16 of 17 OpenStax Microbiology Test Bank Chapter 11: Mechanisms of Microbial Genetics Difficulty: Difficult ASM Standard: 2, 23 This file is copyright 2017, Rice University. All rights reserved. Page 17 of 17