DNA Damage & Carcinogenesis
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Questions and Answers

What is the main focus of the text?

  • The causes of DNA damage
  • The two main categories of DNA damage
  • The genetic stability of DNA
  • The balance of life and DNA repair (correct)

    • What is the only molecule that relies solely on repair of existing molecules?

  • Proteins
  • RNA
  • Lipids
  • DNA (correct)

    • What did Errol Friedberg's review in Nature Reviews Cancer describe?

  • The generation and persistence of mutations for genetic diversity (correct)
  • The types of cancer caused by DNA damage
  • The avoidance of mutations by DNA repair
  • The impact of DNA damage on other cellular responses

    • What are the two main categories of DNA damage mentioned in the learning outcomes?

    <p>Spontaneous and environmental</p> Signup and view all the answers

    Which molecule is constantly being damaged and can accumulate damage over its lifetime?

    <p>DNA</p> Signup and view all the answers

    Which category of DNA damage is more likely to lead to genome mutation?

    <p>Spontaneous (endogenous) damage</p> Signup and view all the answers

    What is the function of the proofreading ability of DNA polymerases in minimizing base misincorporation?

    <p>Reducing the error frequency to 1 in 107 copied nucleotides</p> Signup and view all the answers

    What is the estimated mutation rate due to incorporation error frequency for one cycle of replication by DNA polymerases without proofreading?

    <p>1 in 105 copied nucleotides</p> Signup and view all the answers

    What is the potential consequence of failure to repair single-strand DNA breaks during replication?

    <p>Formation of chromosomal breaks and translocations</p> Signup and view all the answers

    What is the effect of deamination of cytosine during replication?

    <p>Causes a C-T point mutation</p> Signup and view all the answers

    Which of the following is NOT a main type of environmental DNA damage discussed in the text?

    <p>DNA oxidation</p> Signup and view all the answers

    What is the major product formed by simple monofunctional alkylating agents?

    <p>7-alkylguanine</p> Signup and view all the answers

    What are the major sites of alkylation on the DNA bases by simple alkylating agents?

    <p>Guanine-N7 and Adenine-N3</p> Signup and view all the answers

    Which type of adduct formation is highly cytotoxic and makes it hard for the DNA strands to open?

    <p>Interstrand crosslink</p> Signup and view all the answers

    Which chemical is extensively metabolized and can produce highly reactive intermediates that can react with DNA, leading to adduct formation and tumour incidence?

    <p>NNK</p> Signup and view all the answers

    What is the ultimate carcinogen formed following two successive oxidation reactions mediated by cytochrome p450s?

    <p>Benzo[a]pyrenediolepoxide</p> Signup and view all the answers

    Which of the following environmental agents can form bulky adducts on the exocyclic amino group of guanine in the minor groove of DNA?

    <p>Photosensitisation</p> Signup and view all the answers

    What is the mutation usually induced by benzo[a]pyrene, providing clues to the identity of the causative carcinogenic agent?

    <p>G-to-T transversion</p> Signup and view all the answers

    What can result from the stripping of electrons from water molecules by ionising radiation?

    <p>DNA-Protein Cross-Link</p> Signup and view all the answers

    What is the major photoproduct formed by more than 60% of pyrimidine dimers upon UV irradiation of DNA?

    <p>TT dimers</p> Signup and view all the answers

    What is the main purpose of the single cell gel electrophoresis (comet) assay?

    <p>To measure DNA damage and repair at an individual cell level</p> Signup and view all the answers

    What is a key advantage of the comet assay compared to other methods of DNA damage measurement?

    <p>It provides individual cell data</p> Signup and view all the answers

    In the context of tumourigenesis, which stage involves increased genetic instability and susceptibility to further mutations?

    <p>Progression</p> Signup and view all the answers

    Which type of agents are phorbol esters and hormones examples of in the context of tumourigenesis?

    <p>Tumour promoting agents</p> Signup and view all the answers

    What does the left graph show in relation to insulation workers exposed to asbestos?

    <p>The cumulative risk of developing mesothelioma</p> Signup and view all the answers

    What is the main purpose of the comet assay?

    <p>To measure DNA damage at a single cell level</p> Signup and view all the answers

    How does the comet assay quantify DNA damage?

    <p>By analyzing the size and fluorescence of the 'head' and 'tail' of each cell comet</p> Signup and view all the answers

    What is the effect of DNA interstrand crosslinks on the migration of DNA fragments in the comet assay?

    <p>They retard the migration of irradiated DNA fragments</p> Signup and view all the answers

    In the comet assay, what does a high value of 'tail moment' indicate?

    <p>High DNA damage</p> Signup and view all the answers

    What is the purpose of neutralization in the comet assay procedure?

    <p>To remove cellular proteins and lipids</p> Signup and view all the answers

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