Recent

  • Show all results for ""

🎧 New: AI-Generated Podcasts Turn your study notes into engaging audio conversations. Learn more

Genetics Conditional Lethal Mutations
40 Questions
0 Views

Genetics Conditional Lethal Mutations

Created by
@FlatterWashington

Podcast Beta

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What percentage of known carcinogens examined in the initial Ames testing were shown to be strong mutagens?

  • 90%
  • 80% (correct)
  • 75%
  • 60%

    • What is the primary purpose of the Ames test?

  • To confirm carcinogenic properties of compounds
  • To analyze DNA repair mechanisms
  • To serve as a preliminary screening for mutagenicity (correct)
  • To quantify cancer rates in populations

    • Which of the following best describes the relationship between mutations and cancer according to the Ames test findings?

  • Cancer can occur without any mutations
  • Cancer occurs due to cellular transformation caused by mutations (correct)
  • All mutations lead to cancer
  • Mutations are a result of cancer

    • What significant finding regarding cigarette smoke was made through the Ames test?

    <p>More than 60 compounds in it test positive for mutagenicity</p> Signup and view all the answers

    Which type of DNA polymerases are primarily responsible for the proofreading function during DNA replication?

    <p>DNA polymerase I and III</p> Signup and view all the answers

    What is the most straightforward method mentioned for repairing damaged DNA?

    <p>Direct reversal of damaged DNA</p> Signup and view all the answers

    Which statement accurately describes a limitation of the Ames test?

    <p>It can definitively determine if a compound is carcinogenic</p> Signup and view all the answers

    What type of compounds does the Ames test evaluate extensively during development processes?

    <p>Industrial and pharmaceutical chemical compounds</p> Signup and view all the answers

    What characteristic do temperature-sensitive mutants possess?

    <p>They are viable at one temperature and lethal at a different temperature.</p> Signup and view all the answers

    What is the role of Salmonella typhimurium strains in the Ames test?

    <p>They reveal the presence of specific types of mutations.</p> Signup and view all the answers

    What is the significance of the his- strains in the Ames test?

    <p>They require histidine for growth due to genetic mutations.</p> Signup and view all the answers

    What happens when a test compound is incubated with a mammalian liver extract in the Ames test?

    <p>The test compound is converted into more chemically reactive products.</p> Signup and view all the answers

    What type of mutations do the different strains of Salmonella typhimurium detect?

    <p>A variety of specific mutations including both base-pair substitutions and frameshift mutations.</p> Signup and view all the answers

    What do the three termination codons UAG, UAA, and UGA signify in the context of mutations?

    <p>They are known as amber, ochre, and opal, respectively.</p> Signup and view all the answers

    Which of the following statements about suppressor-sensitive mutants is true?

    <p>They rely on external suppressor mutations to survive.</p> Signup and view all the answers

    What is the primary purpose of the Ames test?

    <p>To identify substances that may cause mutations.</p> Signup and view all the answers

    What is the primary function of DNA photolyase in the DNA repair process?

    <p>To cleave covalent bonds linking thymine dimers</p> Signup and view all the answers

    Which type of damage does O6-methylguanine-DNA methyltransferase primarily repair?

    <p>Alkylation products of guanine</p> Signup and view all the answers

    What is required for the efficient operation of DNA photolyase?

    <p>Energy from visible light in the blue spectrum</p> Signup and view all the answers

    What process occurs in base-excision repair?

    <p>A modified base is excised and replaced by a new nucleotide</p> Signup and view all the answers

    How does the enzyme O6-methylguanine-DNA methyltransferase inactivate itself during repair?

    <p>By binding to cysteine and transferring a methyl group</p> Signup and view all the answers

    In which organism is photoreactivation a common mechanism for DNA repair?

    <p>Bacteria such as E. coli</p> Signup and view all the answers

    What is the role of DNA glycosylases in base-excision repair?

    <p>To recognize and excise specific damage types</p> Signup and view all the answers

    What type of repair is primarily irreversible?

    <p>Most types of damage</p> Signup and view all the answers

    What defines a conditional lethal mutation?

    <p>A mutation that shows viability depending on growth conditions.</p> Signup and view all the answers

    Which of the following is NOT a class of conditional lethal mutants?

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

    In which condition do auxotrophic mutants grow normally?

    <p>When the essential metabolite is supplied</p> Signup and view all the answers

    What characterizes temperature-sensitive mutants?

    <p>They grow at one temperature but fail to grow at another.</p> Signup and view all the answers

    What causes the inability of suppressor-sensitive mutants to grow?

    <p>The absence of a suppressor gene.</p> Signup and view all the answers

    What type of mutations do auxotrophs specifically relate to?

    <p>Mutations that prevent synthesis of essential metabolites.</p> Signup and view all the answers

    Which of the following statements about suppressor-sensitive mutations is true?

    <p>They can be corrected by the presence of a second genetic factor.</p> Signup and view all the answers

    Which characteristic is commonly found in temperature-sensitive mutants?

    <p>They often affect enzymes with varying activity at different temperatures.</p> Signup and view all the answers

    Which enzyme is responsible for recognizing and removing uracil during base excision repair?

    <p>Uracil glycosylase</p> Signup and view all the answers

    What enzyme cuts the phosphodiester bond after a base has been removed?

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

    Which DNA polymerase is utilized by eukaryotes during base excision repair?

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

    What is a known limitation of DNA polymerase β?

    <p>It makes mistakes at a rate of one per 4000 nucleotides.</p> Signup and view all the answers

    What happens when DNA polymerase β inserts an incorrect nucleotide?

    <p>AP endonuclease 1 can excise the incorrectly paired base.</p> Signup and view all the answers

    How many base modifications are typically repaired by base excision repair in a day?

    <p>20,000 to 40,000</p> Signup and view all the answers

    What role does DNA ligase play in base excision repair?

    <p>It seals the nick in the sugar-phosphate backbone.</p> Signup and view all the answers

    Which activity is utilized by AP endonuclease 1 to maintain fidelity in base-excision repair?

    <p>Exonuclease activity</p> Signup and view all the answers

    Study Notes

    Conditional Lethal Mutations

    • Conditional lethal mutations are mutations that cause a mutant to be viable in permissive growth condition but not viable in restrictive growth condition.
    • The three major classes of mutants with conditional lethal phenotypes:
      • Auxotrophic mutants
      • Temperature-sensitive mutants
      • Suppressor-sensitive mutants

    Auxotrophic Mutants

    • Auxotrophic mutants are unable to synthesize an essential metabolite required for growth while wild-type organisms can.
    • The growth of auxotrophic mutants can be rescued by supplying the essential metabolite in the medium.

    Temperature-Sensitive Mutants

    • Temperature-sensitive mutants will grow at a permissive temperature, but not at a restrictive temperature.
    • Most are heat-sensitive, but some are cold-sensitive.
    • Temperature sensitivity usually results from the mutant gene product being heat- or cold-labile.

    Suppressor-Sensitive Mutants

    • Suppressor-sensitive mutants are viable only with the presence of a suppressor but not viable without it.
    • The suppressor gene may compensate for the defect caused by the suppressor-sensitive mutation or may render the mutated gene product nonessential.

    Evaluating Mutagens in our Environment by Ames Test

    • The Ames test is a rapid, convenient way to assess mutagenicity.
    • The Ames test uses strains of Salmonella typhimurium that are unable to synthesize histidine (his-) to detect mutations.
    • The test measures the frequency of reverse mutations in the his gene, resulting in wild-type bacteria (his+)
    • his- strains have increased sensitivity to mutagens due to mutations in genes involved in DNA damage repair and the lipopolysaccharide barrier.
    • The Ames test also includes liver extract to mimic metabolic activation of compounds in the human body.

    DNA Repair Pathways

    • The most important DNA repair mechanism is the proofreading function of DNA polymerases.
    • Other DNA repair pathways include:
      • Direct Reversal
      • Excision Repair

    Direct Reversal of Damaged DNA

    • Direct reversal mechanisms directly regenerate the normal base in DNA.
    • Examples
      • Photoreactivation (uses light energy to cleave thymine dimers)
      • Alkyltransferases remove alkyl groups from damaged bases.

    Excision Repair Pathways

    • Excision repair pathways remove the damaged base and replace the entire nucleotide.
    • Base-excision repair:
      • DNA glycosylases remove the damaged base.
      • AP endonucleases cut the phosphodiester bond.
      • DNA polymerase replaces the damaged nucleotide.
      • DNA ligase seals the gap.
    • Base-excision repair relies on DNA polymerase $\beta$ in eukaryotes.
    • DNA polymerase $\beta$ can introduce errors, but AP endonuclease 1 can proofread errors.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Lecture 5 BBT317 Mutation and Repair Part V.pptx

    Description

    Explore the fascinating world of conditional lethal mutations in genetics. This quiz covers the three major classes: auxotrophic, temperature-sensitive, and suppressor-sensitive mutants. Test your understanding of these concepts and their implications in biological research.

    More Quizzes Like This

    Conditional Sentences Quiz
    5 questions

    Conditional Sentences Quiz

    AdventuresomeBlackTourmaline3278 avatar
    AdventuresomeBlackTourmaline3278
    Guide to Conditional Sentences in English
    13 questions

    Conditional Sentences Quiz: Test Your Knowledge

    Teacher_Sean avatar
    Teacher_Sean
    Chapter 2 Section 2: Conditional Statements
    8 questions

    Chapter 2 Section 2: Conditional Statements

    RadiantLaplace9461 avatar
    RadiantLaplace9461
    Conditional Statements Flashcards
    8 questions

    Conditional Statements Flashcards

    WholesomeVibrance avatar
    WholesomeVibrance
    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser