Question 1

Which DNA repair pathway is defective in individuals with Xeroderma pigmentosum, leading to increased sensitivity to UV-induced DNA damage?

Accepted Answer

Nucleotide excision repair (NER)

Question 2

A patient presents with skin cancer and is found to have mutations in the XPA-XPG genes. Which process is most likely impaired?

Accepted Answer

Repair of UV-induced thymine dimers

Question 3

Which enzyme is primarily responsible for filling in the gap after excision of damaged nucleotides during nucleotide excision repair?

Accepted Answer

DNA polymerase I

Question 4

Replication errors that escape proofreading and mismatch repair are corrected by which process?

Accepted Answer

Postreplication repair

Question 5

Which protein is involved in strand invasion during homologous recombination repair of double-stranded DNA breaks?

Accepted Answer

RecA protein

Question 6

Double-stranded breaks in DNA can lead to which of the following outcomes if not properly repaired?

Accepted Answer

Chromosomal rearrangements and cell death

Question 7

Which repair pathway is most likely to introduce mutations at the site of double-stranded DNA breaks?

Accepted Answer

Nonhomologous end-joining (NHEJ)

Question 8

During DNA replication, which type of DNA damage is most likely to occur and require repair?

Accepted Answer

Double-stranded breaks

Question 9

Which of the following best describes the role of DNA ligase in DNA repair?

Accepted Answer

It seals nicks in the sugar-phosphate backbone.

Question 10

A cell is exposed to UV light, resulting in the formation of thymine dimers. Which repair mechanism is most likely to fix this damage in humans?

Accepted Answer

Nucleotide excision repair

Question 11

Which of the following is a multi-step process that involves recognition, excision, and resynthesis of damaged DNA?

Accepted Answer

Nucleotide excision repair

Question 12

If a mutation occurs in the gene encoding RecA protein, which DNA repair pathway would be most affected?

Accepted Answer

Homologous recombination

Question 13

Which of the following equations best represents the process of DNA ligation during repair?

Accepted Answer

$$DNA_{fragment1} + DNA_{fragment2} \rightarrow DNA_{fragment1-fragment2}$$

Question 14

Which repair pathway is most likely to be error-prone and result in small insertions or deletions at the site of repair?

Accepted Answer

Nonhomologous end-joining (NHEJ)

Question 15

A researcher observes that a cell line is unable to repair UV-induced thymine dimers. Which gene family is most likely mutated?

Accepted Answer

XPA-XPG

Question 16

Which of the following is NOT a consequence of double-stranded DNA breaks?

Accepted Answer

Increased transcription

Question 17

Which repair pathway uses a homologous chromosome as a template to accurately repair double-stranded breaks?

Accepted Answer

Homologous recombination

Question 18

Which of the following steps occurs FIRST in nucleotide excision repair?

Accepted Answer

Recognition of damaged DNA

Question 19

Which equation best represents the process of postreplication repair involving strand invasion?

Accepted Answer

$$DNA_{damaged} + DNA_{template} \rightarrow DNA_{repaired}$$

Question 20

Which repair pathway is most likely to be used when a double-stranded break occurs during DNA replication?

Accepted Answer

Homologous recombination

DNA Repair Mechanisms and Double-Stranded Break Repair in Genetics

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