Gene Mutation and DNA Repair Quiz
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Questions and Answers

What is the primary consequence of depurination in DNA?

  • It always results in a translocation mutation.
  • It causes the double helix structure to stabilize.
  • It leads to the formation of an apurinic site. (correct)
  • It prevents the insertion of transposable elements.

    • Which of the following is a common cause of spontaneous mutations?

  • Depurination, deamination, and tautomeric shifts. (correct)
  • DNA proofreading errors during replication.
  • Radiation therapy.
  • Exposure to extreme temperatures.

    • What can happen if a depurination event is not repaired?

  • It leads to the introduction of a complementary base.
  • A mutation may occur due to the absence of a complementary base. (correct)
  • It results in the formation of a tautomeric shift.
  • The DNA becomes more stable and resistant to mutations.

    • What role do chemical agents have in relation to DNA?

    <p>They can cause changes in the DNA structure.</p> Signup and view all the answers

    Which of the following statements about tautomeric shifts is true?

    <p>They are induced by reactive oxygen species produced in metabolism.</p> Signup and view all the answers

    What type of mutation involves the loss of all or part of a chromosome?

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

    Which of the following best describes 'position effect'?

    <p>A gene remains intact but its expression is altered due to a change in location.</p> Signup and view all the answers

    What are germ-line cells responsible for?

    <p>Giving rise to gametes like eggs and sperm</p> Signup and view all the answers

    What can cause induced mutations?

    <p>Environmental agents known as mutagens</p> Signup and view all the answers

    Which type of chromosomal mutation results from a gene moving close to regulatory sequences of another gene?

    <p>Position effect</p> Signup and view all the answers

    What type of mutation can cause changes in the number or structure of chromosomes?

    <p>Chromosomal mutations</p> Signup and view all the answers

    What happens when a chromosomal rearrangement alters the expression of a gene?

    <p>The gene may malfunction, but stays intact.</p> Signup and view all the answers

    What can aberrant recombination during meiosis potentially cause?

    <p>Aneuploidy or polyploidy</p> Signup and view all the answers

    What type of mutation involves a substitution of a single base pair?

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

    Which mutation is characterized by a change from a purine to a pyrimidine?

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

    What is the major consequence of a nonsense mutation?

    <p>It produces a truncated polypeptide.</p> Signup and view all the answers

    Which type of mutation is most likely to produce a completely different amino acid sequence downstream?

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

    Which type of effect does an up promoter mutation have on transcription?

    <p>Enhances the rate of transcription</p> Signup and view all the answers

    What kind of mutation does NOT alter protein function?

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

    What is the effect of a deleterious mutation?

    <p>Lowers chance of survival and reproduction</p> Signup and view all the answers

    Which type of mutation might provide a survival advantage in the presence of malaria?

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

    Which of the following mutations alters the stability of RNA but does not change the amino acid sequence?

    <p>Regulatory element mutation</p> Signup and view all the answers

    What is a characteristic of frameshift mutations?

    <p>They shift the reading frame downstream from the mutation.</p> Signup and view all the answers

    What type of radiation is capable of penetrating deeply into biological materials?

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

    Which type of radiation is primarily responsible for the formation of thymine dimers in DNA?

    <p>UV light</p> Signup and view all the answers

    What is the first step in the DNA repair process?

    <p>An irregularity in DNA structure is detected</p> Signup and view all the answers

    Which DNA repair system involves removing a segment of DNA and using the complementary strand as a template?

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

    Which repair mechanism is specifically used for repairing double-strand breaks in DNA?

    <p>Nonhomologous end joining</p> Signup and view all the answers

    Which type of DNA alteration can ionizing radiation cause?

    <p>Base deletions</p> Signup and view all the answers

    What is the main characteristic that distinguishes nonionizing radiation from ionizing radiation?

    <p>It has longer wavelengths.</p> Signup and view all the answers

    What effect does tanning have on DNA concerning UV light exposure?

    <p>It increases potential for thymine dimers.</p> Signup and view all the answers

    What is the result of deamination of cytosine?

    <p>It produces uracil.</p> Signup and view all the answers

    What problem arises from deamination of 5-methylcytosine?

    <p>It produces thymine, making detection difficult.</p> Signup and view all the answers

    Which of the following is a chemical mutagen that acts as a base analog?

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

    What effect do alkylating agents have on DNA?

    <p>They attach methyl or ethyl groups to bases.</p> Signup and view all the answers

    What occurs during a tautomeric shift of thymine or guanine?

    <p>They change from keto to enol forms.</p> Signup and view all the answers

    How do physical mutagens generally affect DNA?

    <p>They lead to crosslinking and chromosomal breaks.</p> Signup and view all the answers

    What is a characteristic of intercalating agents?

    <p>They distort the helical structure of DNA.</p> Signup and view all the answers

    Which of the following describes base modifiers?

    <p>They covalently modify the structure of nucleotides.</p> Signup and view all the answers

    What could be a consequence if uracil is not repaired in DNA?

    <p>It can result in a mutation during replication.</p> Signup and view all the answers

    5-Bromouracil can lead to mutations by pairing incorrectly due to what process?

    <p>Tautomeric shifts in its structure.</p> Signup and view all the answers

    What enzyme is specifically known for repairing thymine dimers through photoreactivation?

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

    Which DNA repair mechanism is capable of fixing missing bases and cross-links?

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

    Which of the following proteins is NOT part of the Nucleotide Excision Repair system in E. coli?

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

    Inherited defects in genes involved in Nucleotide Excision Repair are associated with which of the following diseases?

    <p>Xeroderma pigmentosum</p> Signup and view all the answers

    What triggers the mismatch repair system to correct base pair mismatches in DNA?

    <p>Proofreading failure by DNA polymerase</p> Signup and view all the answers

    Mismatch repair systems are present in which of the following organisms?

    <p>All species</p> Signup and view all the answers

    Which proteins in E. coli are primarily responsible for recognizing and removing damaged DNA during NER?

    <p>UvrA, UvrB, UvrC, UvrD</p> Signup and view all the answers

    What is the primary cause of base pair mismatches during DNA replication?

    <p>Insertion of incorrect bases</p> Signup and view all the answers

    Study Notes

    Gene Mutation and DNA Repair

    • Mutations are variations in DNA, arising from mistakes during DNA replication.
    • Mutations are changes in the DNA nucleotide sequence and can lead to heritable changes in genetic information.
    • Organisms have evolved DNA repair mechanisms to combat the harmful effects of mutations.

    Types of Mutations

    • Mutations are broadly categorized into gene mutations and chromosomal mutations.
    • Gene mutations affect a single gene, while chromosomal mutations affect whole chromosomes.
    • Gene mutations can further be classified as point mutations (affecting a single base pair) or deletions/insertions (affecting multiple base pairs).

    Point Mutations

    • Point mutations, also known as single nucleotide polymorphisms (SNPs), involve changes in a single base pair.
    • They can be categorized as transitions (pyrimidine to pyrimidine or purine to purine substitution) or transversions (pyrimidine to purine or purine to pyrimidine substitution).
    • Point mutations can lead to different outcomes, ranging from no effect on the amino acid sequence (silent mutations) to significant changes resulting in missense mutations or nonsense mutations.

    Deletions/Insertions

    • Deletions or insertions of base pairs can alter the reading frame (frameshift mutations).
    • Frameshift mutations lead to changes in the amino acid sequence downstream of the mutation, often creating nonfunctional proteins.

    Mutations in Coding Sequences

    • Silent mutations do not alter the amino acid sequence due to the degeneracy of the genetic code.
    • Missense mutations change a single amino acid, potentially affecting protein function.
    • Example: Sickle-cell anemia.
    • Nonsense mutations introduce a premature stop codon, resulting in a truncated polypeptide.

    Mutations in Noncoding Sequences

    • Mutations in non-coding sequences can affect gene expression.
    • Promoter mutations can increase or decrease transcription.
    • Splice junctions mutations can alter RNA stability and translation.

    Mutations' Consequences on Genotype and Phenotype

    • Neutral mutations have no effect on protein function.
    • Deleterious mutations lower survival and reproductive chances.
    • Lethal mutations result in cell or organism death.
    • Beneficial mutations enhance survival and reproductive success.
    • Conditional mutations only affect phenotype under specific environmental conditions.

    Chromosomal Mutations

    • Chromosomal mutations involve changes in the number or structure of chromosomes.
    • Four primary types are deletion, duplication, inversion, and translocation.
    • Deletion involves loss of chromosomal segments.
    • Duplication involves increased copies of chromosomal segments.
    • Inversion involves reversal of segment order.
    • Translocation involves movement of segments to different chromosomes.

    Position Effects

    • Position effects arise when a gene's expression changes due to its new location within the chromosome.
    • Relocation to a heterochromatic region can significantly affect gene expression.

    Mutations in Germ-Line or Somatic Cells

    • Germ-line mutations affect gametes, potentially being passed down through generations.
    • Somatic mutations affect non-reproductive cells and are not heritable.

    Causes of Mutations

    • Mutations can be spontaneous (arising from natural cellular processes) or induced (caused by environmental factors).
    • Spontaneous mutations include depurination, deamination, and tautomeric shifts.
    • Induced mutations can be caused by chemical mutagens (e.g., alkylating agents, intercalating agents, base analogs) or physical mutagens (e.g., ionizing radiation, non-ionizing radiation).

    DNA Repair Mechanisms

    • Living cells have multiple DNA repair systems to counteract mutations and restore the original DNA sequence.
    • Common systems include direct repair, nucleotide excision repair, and mismatch repair.
    • Specific DNA repair proteins recognize, remove, and replace damaged nucleotides in the DNA.

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    Related Documents

    Genetics - BIO310 Gene Mutation and DNA Repair PDF

    Description

    Test your knowledge on gene mutations and DNA repair mechanisms in this quiz. Explore the types of mutations including gene and chromosomal mutations, and understand the significance of point mutations and their classifications. Ideal for students studying genetics or molecular biology.

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