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Which of the following is a protein that facilitates the termination of replication in E. coli?


A) telomerase
B) DNA gyrase
C) Tus
D) primase
E) topoisomerase

F) A) and D)
G) All of the above

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What type of synthesis occurs on the leading strand?


A) conservative
B) dispersive
C) continuous
D) discontinuous
E) recombinant

F) B) and D)
G) D) and E)

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What is the function of DNA ligase?


A) connects Okazaki fragments by sealing nicks in the sugar-phosphate backbone
B) unwinds the double helix by breaking the hydrogen bonding between the two strands at the replication fork
C) reduces the torsional strain that builds up ahead of the replication fork as a result of unwinding
D) binds to oriC and causes a short section of DNA to unwind
E) prevents the formation of secondary structures within single-stranded DNA

F) None of the above
G) A) and E)

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What is the function of DNA gyrase?


A) connects Okazaki fragments by sealing nicks in the sugar-phosphate backbone
B) unwinds the double helix by breaking the hydrogen bonding between the two strands at the replication fork
C) reduces the torsional strain that builds up ahead of the replication fork as a result of unwinding
D) binds to oriC and causes a short section of DNA to unwind
E) prevents the formation of secondary structures within single-stranded DNA

F) C) and D)
G) C) and E)

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Explain the effect on DNA replication of mutations that destroy each of the following activities in DNA polymerase. Also, for each kind of mutation, how might you detect the effect in an in vitro replication reaction? a. 5'to 3' polymerase b. 5'to 3' exonuclease c. 3' to 5' exonuclease

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a. If the 5' to 3' polymerase activity o...

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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 seconds
B) 15 seconds
C) 30 seconds
D) 1 minute
E) 2 minutes

F) B) and E)
G) A) and E)

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Which of the following statements is TRUE of DNA polymerases of eukaryotic cells?


A) The same DNA polymerase replicates mitochondrial, chloroplast, and nuclear DNA.
B) There are only two different DNA polymerases that function in the process of replication.
C) Some DNA polymerases have the ability to function in DNA repair mechanisms.
D) All eukaryotic DNA polymerases have 3' \rightarrow 5' exonuclease activity.
E) Leading strand synthesis and lagging strand synthesis are performed by the same type of DNA polymerase.

F) B) and C)
G) B) and E)

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(a) Explain the significance of telomerase in cells of the germ line. (b) Explain the significance of telomerase in cancer cells.

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Telomerase is an enzyme that plays a sig...

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Are Okazaki fragments formed on the leading strand during DNA replication? Explain your answer.

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No, Okazaki fragments are not formed on ...

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Which of the following enzyme and function pairs is INCORRECTLY matched?


A) DNA gyrase; making and resealing the break to remove the torque as the DNA unwinds
B) DNA ligase; sealing nicks in the sugar-phosphate backbone of newly synthesized DNA
C) DNA helicase; rewinding and reforming the DNA double helix as the replication terminates
D) DNA polymerase III; elongating a new nucleotide strand from the 3'-OH provided by the primers
E) Initiator protein; binding to replication origin and separating DNA to initiate replication

F) All of the above
G) C) and E)

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C

DNA primase requires a _____ template and _____ nucleotides to initiate primer synthesis.


A) DNA; DNA
B) RNA; RNA
C) DNA; RNA
D) RNA; DNA
E) leading strand; DNA

F) C) and D)
G) B) and C)

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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 seconds
B) 15 seconds
C) 30 seconds
D) 1 minute
E) 2 minutes

F) None of the above
G) D) and E)

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You discover a drug that specifically inhibits DNA synthesis. You apply the drug to yeast cells after S phase but before prophase of meiosis. You find a drastic reduction in recombination in the meiotic products. How can you explain this?

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The discovery of a drug that specificall...

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If ribonucleotides were depleted from a cell during S phase, how would DNA synthesis be affected? (Ignore energetic considerations.)


A) There would be no effect because ribonucleotides are used in RNA synthesis, not DNA synthesis.
B) DNA synthesis would continue but at a slower rate.
C) There would only be an effect during M phase, not in S phase.
D) DNA synthesis would not be affected because ribonucleotides are only used during the process of transcription.
E) Replication would cease because ribonucleotides are required to initiate DNA synthesis.

F) B) and E)
G) B) and D)

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E

During DNA replication, the synthesis of the new strand requires the addition of a new dNTP to the 3ʹ-OH group of the growing nucleotide strand by DNA polymerase. Which of the following provides the energy needed for this step?


A) the template strand
B) the energy of pentose sugar
C) 5ʹ end of the growing DNA
D) cleavage of two phosphate groups from the dNTP
E) The reaction does not require an energy source.

F) D) and E)
G) A) and B)

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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 Moderate with nucleotides that are not radioactive so that newly synthesized DNA will not be radioactive. What proportion of DNA molecules will contain radioactivity after two rounds of replication?


A) 0
B) 1/8
C) 1/4
D) 1/3
E) 1/2

F) A) and D)
G) C) and D)

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Which of the following does NOT utilize bidirectional replication?


A) theta model
B) rolling-circle model
C) linear model
D) eukaryotes
E) bacteria

F) B) and D)
G) C) and D)

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DNA synthesis during replication is initiated from:


A) a free 5' OH.
B) DNA primers.
C) RNA primers.
D) telomerase.
E) DNA polymerase I.

F) C) and D)
G) A) and B)

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Discuss the main differences in the initiation of recombination proposed by the Holliday model and the double-stranded-break model.

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The Holliday model and the double-strand...

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You have discovered a special dye that reveals the position of recombination sites on meiotic chromosomes. You use this dye to count the number of recombination sites and then compare this to the number of genetic exchanges that you can detect by looking at the segregation of markers across the genome. You find many more recombination sites as compared to genetic exchanges. Explain this result.

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The discrepancy between the number of recombination sites and the number of genetic exchanges can be explained by the occurrence of multiple recombination events at a single site. During meiosis, homologous chromosomes undergo genetic recombination, where segments of DNA are exchanged between maternal and paternal chromosomes. This process creates new combinations of genetic material and contributes to genetic diversity. The special dye that reveals recombination sites allows for the direct visualization of these events on meiotic chromosomes. However, it is possible for multiple recombination events to occur at the same physical location on a chromosome, resulting in the detection of more recombination sites than the actual number of genetic exchanges. Additionally, the resolution of the dye may allow for the detection of smaller recombination events that do not result in observable genetic exchanges. These smaller events may not lead to detectable changes in the segregation of genetic markers across the genome, leading to a discrepancy between the number of recombination sites and genetic exchanges. Overall, the discrepancy between the number of recombination sites and genetic exchanges can be attributed to the complexity of meiotic recombination and the limitations of detection methods. It highlights the intricacies of genetic recombination and the need for comprehensive approaches to studying these processes.

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