BLOCK 3: MBG: (3.3) DNA: DNA DAMAGE & REPAIR
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BLOCK 3: MBG: (3.3) DNA: DNA DAMAGE & REPAIR

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Questions and Answers

What defines a missense mutation?

  • It leads to a codon that codes for a different amino acid. (correct)
  • It results in a premature stop codon.
  • It does not change the amino acid sequence.
  • It involves a shift in the reading frame.

    • Which of the following mutations results in a change of the reading frame?

  • Frameshift mutation. (correct)
  • Silent mutation.
  • Missense mutation.
  • Nonsense mutation.

    • What is the primary consequence of errors during DNA replication?

  • No effect on the DNA sequence.
  • Potential changes in the sequence that affect protein products. (correct)
  • Immediate repair by DNA ligase.
  • Increased fidelity of future replications.

    • Which DNA repair mechanism primarily corrects base pair mismatches introduced during replication?

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

    Which environmental factor is known to cause DNA damage through ionizing radiation?

    <p>X-rays.</p> Signup and view all the answers

    What is the primary responsibility of Base Excision Repair (BER)?

    <p>Removing non-helix-distorting changes affecting individual bases</p> Signup and view all the answers

    Which mechanism is directly responsible for fixing thymine dimers caused by UV damage?

    <p>Direct Repair</p> Signup and view all the answers

    How does Nucleotide Excision Repair (NER) recognize DNA damage?

    <p>Through key proteins binding to stalled transcription machinery</p> Signup and view all the answers

    What type of DNA lesion is primarily associated with Homologous Recombination (HR)?

    <p>Double strand breaks</p> Signup and view all the answers

    What distinguishes global genome repair from transcription-coupled repair in NER?

    <p>Global genome repair occurs without association with transcription</p> Signup and view all the answers

    Which DNA repair mechanism can involve repair of interstrand crosslinks?

    <p>Interstrand Crosslink Repair</p> Signup and view all the answers

    What type of mutation is primarily repaired by Mismatch Repair (MMR)?

    <p>Mismatched bases during DNA replication</p> Signup and view all the answers

    Which of the following is a consequence of defects in DNA repair mechanisms?

    <p>Increased susceptibility to DNA mutations</p> Signup and view all the answers

    What type of damage does Direct Repair specifically address?

    <p>Altered bases</p> Signup and view all the answers

    Which repair mechanism is linked to cognitive impairment and neurodegenerative diseases?

    <p>Base Excision Repair</p> Signup and view all the answers

    What is an essential feature of Nonhomologous End Joining (NHEJ)?

    <p>It can repair any double strand break</p> Signup and view all the answers

    What characterizes the repair action of Base Excision Repair (BER)?

    <p>It uses DNA N-glycosylases to remove altered bases</p> Signup and view all the answers

    Which of the following processes helps in the repair of bulky, helix-distorting DNA lesions like thymine dimers?

    <p>Nucleotide Excision Repair</p> Signup and view all the answers

    Which of the following is a fundamental component for the recognition of mismatched bases in mismatch repair?

    <p>MutS homologs (MSH)</p> Signup and view all the answers

    What process is directly involved in repairing interstrand crosslinks?

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

    During which step of homologous recombination is the strand from a homologous template used in repair?

    <p>Synthesis of strand</p> Signup and view all the answers

    What is the primary function of nucleotide excision repair (NER)?

    <p>Repair bulky, helix-distorting damage</p> Signup and view all the answers

    Which repair mechanism removes more than one base to correct an error?

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

    Which of the following steps is NOT involved in non-homologous end joining (NHEJ)?

    <p>Strand invasion</p> Signup and view all the answers

    What is one major consequence of errors in DNA replication if not corrected?

    <p>Mutation accumulation</p> Signup and view all the answers

    The repair mechanism that primarily recognizes and repairs double strand breaks is called what?

    <p>Non-homologous end joining</p> Signup and view all the answers

    What type of damage is specifically repaired through the mechanism of base excision repair (BER)?

    <p>Altered bases</p> Signup and view all the answers

    Which of the following mechanisms can cross over with nucleotide excision repair (NER)?

    <p>Homologous recombination</p> Signup and view all the answers

    Which disorder is associated with defective mismatch repair (MMR) mechanisms?

    <p>Cancer predisposition</p> Signup and view all the answers

    What is the central role of exonucleases in mismatch repair?

    <p>Remove mismatched bases</p> Signup and view all the answers

    What is a key feature of non-homologous end joining (NHEJ)?

    <p>Connects broken ends without need for sequence homology</p> Signup and view all the answers

    Which type of damage can lead to stalling during replication and is specifically recognized by interstrand crosslink repair mechanisms?

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

    Study Notes

    Mutation Types

    • Mutations are classified based on changes to DNA sequence
    • Silent: DNA sequence change but no change in protein sequence
    • Missense: Change in DNA sequence results in different amino acid in a protein
    • Nonsense: Change in DNA sequence causes premature stop codon, resulting in a shortened protein
    • Frameshift: Insertion or deletion of nucleotides that are not a multiple of 3, leading to a shift in reading frame
    • Deleterious: Mutation that negatively affects a cell or organism
    • Beneficial: Mutation that is advantageous for a cell or organism

    DNA Repair Mechanisms

    • Direct Repair: Chemical alteration of a damaged base to restore its original structure
    • Base Excision Repair (BER): Removal of damaged bases by DNA glycosylases
    • Nucleotide Excision Repair (NER): Removal and replacement of damaged DNA segments
    • Mismatch Repair (MMR): Correction of mismatched base pairs during DNA replication
    • Interstrand Crosslink Repair (ICL): Repairs crosslinks between DNA strands
    • Homologous Recombination (HR): Repair of double-stranded breaks using a homologous template
    • Non-homologous End Joining (NHEJ): Joining of broken DNA ends without requiring homology

    Errors during Replication

    • Tautomeric Shifts: Temporary changes in base structure (e.g., keto-enol, amino-imino)
    • Spontaneous Deamination: Loss of an amino group from a base (e.g., cytosine deaminates to uracil)

    Exogenous DNA Damage

    • Ionizing Radiation: Creates double-strand breaks, base modifications, and crosslinks
    • UV Damage: Forms thymine dimers
    • Alkylating Agents: Add alkyl groups to bases, causing mutations
    • Polycyclic Aromatic Hydrocarbons: Create bulky adducts that disrupt DNA structure

    Endogenous DNA Damage

    • Reactive Oxygen Species (ROS): Generated during metabolism, causing base modifications and strand breaks
    • Replication Errors: Mistakes during DNA synthesis

    Consequences of Mutations

    • Changes to DNA structure and sequence
    • Altered protein structure and function
    • Potential for further mutations
    • Disease development
    • Beneficial adaptation

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    Related Documents

    BMS 532 DNA Damage and Repair Lecture Notes PDF

    Description

    This quiz covers essential concepts related to mutation types and DNA repair mechanisms. It explores different mutation classifications, including silent, missense, and frameshift mutations, alongside DNA repair processes such as direct repair and nucleotide excision repair. Test your understanding of these fundamental topics in genetics.

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