DNA Mutation Causes
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Questions and Answers

What are spontaneous mutations primarily caused by?

  • Mechanical damage to DNA
  • Errors during DNA replication (correct)
  • Environmental stressors
  • Chemical mutagens

    • Which of the following contributes to the occurrence of strand-slippage during DNA replication?

  • Presence of base analogs
  • Regions with small repeated sequences (correct)
  • High temperatures during replication
  • Regions with single nucleotide repeats

    • What type of shift leads to errors during DNA replication, potentially leading to mutations?

  • Covalent modifications
  • Hydrogen bonding alterations
  • Base tautomerism (correct)
  • Reverse transcription errors

    • Which of the following is NOT considered a physical mutagen?

    <p>Intercalating agents</p> Signup and view all the answers

    How can mutations potentially affect an organism if not repaired?

    <p>They can lead to disease or death.</p> Signup and view all the answers

    What is the result of heat causing detachment of bases in nucleotides?

    <p>An AP site is created</p> Signup and view all the answers

    Which mutagen causes base dimerization in DNA?

    <p>Ultraviolet radiation</p> Signup and view all the answers

    What effect does deamination of cytosine have on DNA replication?

    <p>It produces uracil, which pairs with adenine.</p> Signup and view all the answers

    Which of the following is an example of an intercalating agent?

    <p>Ethidium bromide</p> Signup and view all the answers

    What is a consequence of deaminating agents on adenine?

    <p>Adenine is converted to hypoxanthine, pairing with cytosine.</p> Signup and view all the answers

    What is the result of deamination of adenine in DNA?

    <p>It pairs with C</p> Signup and view all the answers

    Which tautomer of adenine can pair with cytosine instead of thymine?

    <p>Imino-adenine</p> Signup and view all the answers

    How does 5-bromouracil induce mutations during DNA replication?

    <p>It can mispair with guanine.</p> Signup and view all the answers

    What effect do deaminating agents have on cytosine?

    <p>They convert it into uracil.</p> Signup and view all the answers

    What is a characteristic of intercalating agents?

    <p>They insert between base pairs.</p> Signup and view all the answers

    What type of mutation is primarily caused by alkylating agents?

    <p>Transition mutation</p> Signup and view all the answers

    Which of the following statements regarding UV radiation is true?

    <p>It causes base dimerization.</p> Signup and view all the answers

    Which base analog mimics thymine in DNA?

    <p>5-bromouracil</p> Signup and view all the answers

    What type of mutation does hypoxanthine cause when it pairs with C?

    <p>Transition mutation</p> Signup and view all the answers

    What is a significant consequence of the keto form of thymine during replication?

    <p>It can mispair with guanine.</p> Signup and view all the answers

    What distinguishes the endonuclease function in human mismatch repair from that in E. coli?

    <p>Humans utilize a protein different from MutH as an endonuclease.</p> Signup and view all the answers

    What role do telomeres play in the context of nonhomologous end joining?

    <p>They identify natural ends of chromosomes.</p> Signup and view all the answers

    Which repair mechanism is not methylation-influenced in humans?

    <p>Mismatch repair</p> Signup and view all the answers

    What is a significant risk factor for individuals with Xeroderma pigmentosum (XP)?

    <p>Higher probability of skin and mucous membrane cancer.</p> Signup and view all the answers

    How does the function of DNA ligase relate to nonhomologous end joining?

    <p>It joins breaks in DNA by sealing the ends together.</p> Signup and view all the answers

    What is the initial step in base excision repair in E.coli?

    <p>Removal of the damaged base by DNA glycosylase</p> Signup and view all the answers

    What causes an apurinic/apyrimidinic (AP) site in DNA?

    <p>Heat detachment of bases</p> Signup and view all the answers

    Which enzyme is involved in nucleotide excision repair in E.coli?

    <p>UvrABC endonuclease</p> Signup and view all the answers

    How does E.coli distinguish between the parent strand and the daughter strand during mismatch repair?

    <p>By methylation of the parent strand</p> Signup and view all the answers

    Which repair mechanism directly involves recognition of mismatches by specific enzymes?

    <p>Mismatch repair</p> Signup and view all the answers

    What is the consequence of deamination of adenine in DNA?

    <p>It pairs with cytosine instead of thymine</p> Signup and view all the answers

    Which of the following is a potential effect of intercalating agents on DNA?

    <p>Alteration of the DNA structure leading to replication errors</p> Signup and view all the answers

    In E.coli, what mechanism is primarily utilized to correct errors during DNA replication?

    <p>Mismatch repair</p> Signup and view all the answers

    What is a common consequence of inadequate DNA repair mechanisms?

    <p>Increased frequency of mutations</p> Signup and view all the answers

    Which repair method involves the removal of a single altered base in DNA?

    <p>Base excision repair</p> Signup and view all the answers

    What is the role of the MGMT enzyme in DNA repair?

    <p>It removes alkyl groups from position 6 of G.</p> Signup and view all the answers

    Why is ultraviolet (UV) radiation particularly hazardous for humans?

    <p>Humans rely solely on nucleotide excision repair, which is less efficient.</p> Signup and view all the answers

    Which of the following best describes alkylating agents?

    <p>They induce nucleotide alterations that can lead to mutations.</p> Signup and view all the answers

    What type of mutation is often associated with the action of intercalating agents?

    <p>Frameshift mutations due to insertion or deletion</p> Signup and view all the answers

    Which of the following can result from the action of deaminating agents on cytosine?

    <p>Conversion of cytosine to uracil</p> Signup and view all the answers

    What is the approximate frequency of DNA lesions occurring in human cells daily?

    <p>20,000 - 50,000 lesions per cell per day</p> Signup and view all the answers

    Study Notes

    DNA Mutation Causes

    • A mutation is a change in the nucleotide sequence of a DNA molecule.
    • Mutations can occur due to errors during DNA replication or from mutagens.

    Spontaneous Mutations

    • Some mutations result from errors during DNA replication.
    • These errors are called spontaneous mutations.
    • DNA polymerases typically have proofreading abilities to prevent errors, but sometimes mistakes still occur.
    • Strand slippage is a type of replication error.
    • This is particularly common in regions with repeating sequences. Replication errors can cause either an extra nucleotide or a missing nucleotide on the new DNA strand.
    • Base tautomerism, where a base exists in a different isomeric form, can also cause errors by pairing with the incorrect base during replication. The altered base pairs with a different base than it normally would, leading to a mutation.

    Mutagens and Their Effects

    • Mutagens (chemical or environmental agents) change DNA structures.
    • Base analogs (like 5-bromouracil) mimic natural bases, causing incorrect base pairings and mutations during replication. 5-bromouracil is a thymine analog and can pair with adenine instead of thymine. The enol form of 5-bromouracil is more common and incorrectly pairs with guanine.
    • Deaminating agents (like nitrous acid and sodium bisulphite) alter some nucleotide structures, causing mispairing. Deamination of adenine produces hypoxanthine which pairs with cytosine instead of thymine. Cytosine deamination produces uracil, pairing with adenine instead of guanine. Guanine deamination creates xanthine, which blocks DNA replication.
    • Alkylating agents (e.g. ethylmethane sulphonate) add alkyl groups to nucleotides, leading to transition mutations.
    • Intercalating agents (e.g. ethidium bromide) insert between base pairs, causing insertion mutations.
    • Ultraviolet radiation causes base dimerization (e.g., thymine dimers), which alters DNA structure.
    • Heat causes detachment of bases which can cause an AP site. An AP site is an apurinic/apyrimidinic site, also known as an abasic site.

    Damage Repair

    • Understanding DNA damage is vital for prevention and repair mechanisms.
    • The specific type and magnitude of DNA damage influence repair efficiency.
    • Repair mechanisms exist for different types of DNA damage. Examples include direct repair, excision repair (base and nucleotide), mismatch repair, and non-homologous end joining. These each have specific steps.

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    Related Documents

    BIOL10221 2024 Molecular Biology Lecture 1: Causes of DNA Mutation PDF
    Molecular Biology: DNA Repair Mechanisms (BIOL10221 2024)

    Description

    Explore the various causes of DNA mutations in this quiz. Learn about spontaneous mutations resulting from replication errors and the role of mutagens. Understand how these changes impact genetic information and lead to mutations.

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