DNA Replication, Repair, and Recombination

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Questions

Question 1

What is the approximate mutation rate observed in bacteria like E. coli when corrected for silent mutations and normalized per nucleotide copied?

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Question 2

In eukaryotes, what is the approximate length of Okazaki fragments found on the lagging strand during DNA replication?

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Question 3

What is the primary function of single-strand DNA-binding (SSB) proteins during DNA replication?

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Question 4

What is the combined accuracy of DNA replication after all three steps of proofreading (polymerization, exonucleolytic proofreading, and mismatch repair) are completed?

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Question 5

How does the strand-directed mismatch repair system in E. coli distinguish the newly synthesized DNA strand from the old template strand?

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Question 6

What is the role of DNA topoisomerase I in relieving the 'winding problem' during DNA replication?

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Question 7

Approximately how many origins of replication are used each time a human cell divides?

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Question 8

What is the function of the enzyme telomerase?

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Question 9

What is the most frequent type of spontaneous DNA damage that occurs in human cells, happening about 18,000 times per cell per day?

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Question 10

Which DNA repair pathway is primarily responsible for removing bulky lesions, such as those caused by sunlight or large hydrocarbons?

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Question 11

What is a key difference in the initiation of replication between bacteria and eukaryotes regarding the helicase?

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Question 12

What is the primary mechanism used by translesion polymerases to replicate through damaged DNA?

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Question 13

Which of the following is the 'quick and dirty' solution for repairing double-strand breaks and is predominant in mammalian somatic cells?

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Question 14

What is the key role of the RecA/Rad51 protein in homologous recombination?

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Question 15

What is a Holliday junction?

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Question 16

What is the primary mechanism by which DNA-only transposons move in the cut-and-paste transposition pathway?

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Question 17

What type of enzyme is central to the life cycle of a retrovirus like HIV, responsible for converting its RNA genome into DNA?

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Question 18

What is the approximate rate of movement of a eukaryotic replication fork?

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Question 19

How many subunits compose the eukaryotic CMG helicase?

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Question 20

What is the consequence of a mutation in the human Brca1 or Brca2 genes?

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Question 21

In the process of base excision repair, what is the role of the enzyme AP endonuclease?

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Question 22

In homologous recombination during meiosis, what specialized protein complex is responsible for creating the initial programmed double-strand break?

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Question 23

What is the typical length of the RNA primers synthesized by DNA primase in eukaryotic cells?

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Question 24

How many times per second does the DNA in an isolated nucleosome unwrap from each end?

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Question 25

What is the consequence of 'gene conversion' during meiotic recombination?

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Question 26

Which class of transposable elements predominates in bacteria and is largely responsible for the spread of antibiotic resistance?

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Question 27

What is the key structural feature of the protein-DNA filament formed by RecA/Rad51 that facilitates strand invasion?

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Question 28

What is the main reason that DNA replication in eukaryotes is confined to the S phase of the cell cycle?

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Question 29

How many histone proteins are found in the core of a single nucleosome?

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Question 30

What happens to the parental H3-H4 tetramers and H2A-H2B dimers when a replication fork passes through a nucleosome?

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Question 31

What is the primary consequence for a cell if the ATM protein is defective, as seen in the disease ataxia telangiectasia (AT)?

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Question 32

In the mechanism for nonretroviral retrotransposition, what serves as the primer for the reverse transcription step?

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Question 33

What is the typical size range of the human telomeric repeat sequence GGGTTA?

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Question 34

What is the 'end-replication problem' that eukaryotes solve using telomeres and telomerase?

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Question 35

In the process of repairing a stalled replication fork via 'fork reversal', what acts as the template for the DNA synthesis that bypasses the damage?

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Question 36

What is the role of the clamp loader in DNA replication?

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Question 37

What type of chemical reaction does a DNA glycosylase catalyze in base excision repair?

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Question 38

How much of the human genome is estimated to be composed of recognizable relics of past transposition events?

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Question 39

Which type of mobile genetic element is responsible for generating I elements in Drosophila and L1 elements in humans?

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Question 40

What is the primary distinguishing feature of conservative site-specific recombination compared to transposition?

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Question 41

By the age of 70, a typical human somatic cell is estimated to contain more than how many 'scars' from inaccurate repair by nonhomologous end joining?

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Question 42

What is the function of the Ku protein in nonhomologous end joining?

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Question 43

During which cell-cycle phases is homologous recombination predominantly used to repair double-strand breaks?

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Question 44

What is the function of the enzyme DNA gyrase in bacteria?

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Question 45

Why is an erasable RNA primer thought to be advantageous for DNA replication compared to a DNA primer?

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Question 46

What is the typical total length of Okazaki fragments synthesized by Pol-delta in eukaryotes?

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Question 47

The accidental deamination of 5-methylcytosine in vertebrate DNA produces which natural nucleotide?

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Question 48

According to the text, how do RNA-only viruses like SARS-CoV-2 achieve proofreading during the replication of their RNA genomes?

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Question 49

What is the primary role of the protein shelterin?

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Question 50

What triggers the termination of DNA replication in eukaryotes?

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