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The Griffith Experiment quiz #1

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  • What is the outcome when mice are injected with only the R strain of Streptococcus pneumoniae in the Griffith experiment?
    When mice are injected with only the R strain (nonlethal rough strain) of Streptococcus pneumoniae, the mice remain alive because the R strain does not cause disease.
  • What is the result when mice are injected with only the S strain of Streptococcus pneumoniae in Griffith's experiment?
    The mice die because the S strain is lethal due to its capsule, which protects it from the host's immune system.
  • What happens when mice are injected with only heat-killed S strain bacteria in Griffith's experiment?
    The mice remain alive because the heat-killed S strain cannot reproduce or cause disease.
  • What was the unexpected outcome when Griffith injected mice with both R strain and heat-killed S strain?
    The mice died, and living S strain bacteria were recovered from the dead mice, indicating transformation had occurred.
  • What does the term 'transformation' mean in the context of Griffith's experiment?
    Transformation refers to bacteria uptaking external DNA from their environment, resulting in genotypic and phenotypic changes.
  • Why was the S strain of Streptococcus pneumoniae lethal to mice?
    The S strain has a smooth capsule that protects it from the host's immune system, making it capable of causing lethal infection.
  • Who later identified the transforming substance in Griffith's experiment as DNA?
    Oswald Avery, Macklin McCarty, and Colin MacLeod identified DNA as the transforming substance.
  • Why did some scientists remain skeptical that DNA was the genetic material after Griffith's experiment?
    Many scientists knew more about proteins and considered them better candidates for genetic material than DNA, which was less understood at the time.
  • What genotypic and phenotypic change occurred in the R strain after transformation in Griffith's experiment?
    The R strain acquired the genetic material from the S strain, converting into a lethal S strain with a smooth capsule.
  • What did Griffith conclude about the ability of bacteria from his experiment?
    Griffith concluded that bacteria can uptake and incorporate genetic material from their environment, leading to transformation.