Test Bank forChapter 12: DNA Replication and RecombinationOkazaki fragmentsTest Bank for Chapter 12: DNA Replication and RecombinationMultiple-Choice Questions1. All DNA polymerases synthesize new DNA by adding nucleotides to the _____ of the growing DNA chain.a. 3′ OH b. 5′ OHc. 3′ phosphated. 5′ phosphatee. nitrogenous baseAnswer: aSection 12.2Comprehension Question2. Okazaki fragments are found in all of the following EXCEPTa. leading strand.b. lagging strand.c. eukaryotic DNA.d. bacterial DNA.e. linear replication models.Answer: aSection 12.2Comprehension Question3. Which of the following does NOT utilize bidirectional replication?a. Theta modelb. Rolling circle modelc. Linear modeld. Eukaryotese. BacteriaAnswer: bSection 12.2Comprehension Question4. Which of the following typically only has one origin of replication?a. Prokaryotesb. Eukaryotesc. Linear model of replicationd. Humanse. PlantsAnswer: aSection 12.2Comprehension Question5. Meselson and Stahl showed that DNA is replicated by a __________ system.a. conservativeb. semiconservativec. dispersived. semidispersivee. conservative in prokaryotes and dispersive in eukaryotesAnswer: bSection 12.2Comprehension Question6. What type of synthesis occurs on the leading strand?a. Conservativeb. Dispersivec. Continuousd. Discontinuouse. RecombinationAnswer: cSection 12.2Comprehension Question7. In the diagram below, which letter indicates the 5′ end of the leading strand?a. Ab. Bc. Cd. De. C and DAnswer: cSection 12.2Comprehension Question8. Suppose that some cells are grown in culture in the presence of radioactive nucleotides for many generations so that both strands of every DNA molecule include radioactive nucleotides. The cells are then harvested and placed in new medium with nucleotides that arenot radioactive so that newly synthesized DNA will not be radioactive. What proportion of DNA molecules will contain radioactivity after two rounds of replication?a. 0b. 1/8c. 1/4d. 1/3e. 1/2Answer: eSection 12.2Application Question9. You learn that a Mars lander has retrieved a bacterial sample from the polar ice caps. You obtain a sample of these bacteria and perform the same kind of experiment that Meselson andStahl did to determine how the Mars bacteria replicate their DNA. Based on the following equilibrium density gradient centrifugation results, what type of replication would you propose for these new bacteria?a. Conservativeb. Semiconservativec. Dispersived. Semiconservative or Dispersivee. Conservative or DispersiveAnswer: cSection 12.2Application Question10. You are studying a new virus with a DNA genome of 12 Kb. It can synthesize DNA at a rate of 400 nucleotides per second. If the virus uses rolling-circle replication, how long will it take to replicate its genome?a. 7.5 secondsb. 15 secondsc. 30 secondsd. 1 minutee. 2 minutesAnswer: cSection 12.2Application Question11. You are studying a new virus with a DNA genome of 12 Kb. It can synthesize DNA at a rate of 400 nucleotides per second. If the virus uses theta replication, how long will it take to replicate its genome?a. 7.5 secondsb. 15 secondsc. 30 secondsd. 1 minutee. 2 minutesAnswer: bSection 12.2Application Question12. The nuclear genome of a single human cell (i.e., the entire diploid complement) contains about 6.6 billion (6.6 × 109) base pairs of DNA. If synthesis at each replication fork occurs at an average rate of 50 nucleotides per second, all the DNA is replicated in 5 minutes. Assume that replication is initiated simultaneously at all origins. How many origins of replication exist in a human diploid genome? a. 220,000b. 440,000c. 880,000d. 2.64 x 107e. 1.32 x 108Answer: aSection 12.2Application Question13. The nuclear genome of a single human cell (i.e., the entire diploid complement) contains about 6.6 billion (6.6 × 109) base pairs of DNA. If synthesis at each replication fork occurs at an average rate of 50 nucleotides per second, all the DNA is replicated in 5 minutes. Assume that replication is initiated simultaneously at all origins. Assuming that the origins are approximately equally distributed across the chromosomes, what is the average number of origins per human chromosome?a. 4783b. 19,130c. 4.6 x 106d. 1.21 x 109e. 2.9 x 1010Answer: aSection 12.2Application Question14. Suppose Meselson and Stahl had obtained the following results in their experiment. These results would be consistent with which model of replication?a. Conservative replication onlyb. Semiconservative and conservative replicationc. Semiconservative replication onlyd. Dispersive replication onlye. Semiconservative and dispersive replicationAnswer: eSection 12.2Application Question15. Which of the following enzymes do NOT aid in unwinding of DNA for replication?a. Helicaseb. Single-stranded binding proteinsc. Primased. Gyrasee. TopoisomeraseAnswer: cSection 12.3Comprehension Question16. DNA polymerase I and DNA polymerase III both have ______but only DNA polymerase I has _______.before replicationafter one replicationa. 5′→ 3′ exonuclease activity; 3′→5′ exonuclease activityb. 5′→ 3′ polymerase activity; 3′→5′ polymerase activity c. 3′→5′ polymerase activity; 5′→ 3′ polymerase activity d. 3′→5′ exonuclease activity; 5′→ 3′ exonuclease activity e. 5′→ 3′ polymerase activity; 3′→5′ exonuclease activity Answer: dSection 12.3Comprehension Question17. What is the function of DNA gyrase?a. Connects Okazaki fragments by sealing nicks in the sugar- phosphate backboneb. Unwinds the double helix by breaking the hydrogen bonding between the two strands at the replication forkc. Reduces the torsional strain that builds up ahead of the replication fork as a result of unwindingd. Binds to oriC and causes a short section of DNA to unwinde. Prevents the formation of secondary structures within single-stranded DNAAnswer: cSection 12.3Comprehension Question18. What is the function of single-strand-binding proteins?a. Connects Okazaki fragments by sealing nicks in the sugar- phosphate backboneb. Unwinds the double helix by breaking the hydrogen bonding between the two strands at the replication forkc. Reduces the torsional strain that builds up ahead of the replication fork as a result of unwindingd. Binds to oriC and causes a short section of DNA to unwinde. Prevents the formation of secondary structures within single-stranded DNAAnswer: eSection 12.3Comprehension Question19. What is the function of DNA ligase?a. Connects