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Lambda Bacteriophage and Life Cycle Regulation quiz

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  • What are the two life cycles that Lambda Bacteriophage can enter?
    Lambda Bacteriophage can enter the lytic cycle (active replication and cell lysis) or the lysogenic cycle (viral DNA integrates into the host genome and remains dormant).
  • What environmental conditions favor the lytic cycle in Lambda Bacteriophage?
    Good growth conditions with abundant nutrients favor the lytic cycle by increasing Cro protein levels.
  • Which protein promotes the lysogenic cycle in Lambda Bacteriophage?
    The CI (lambda) protein promotes the lysogenic cycle by inhibiting transcription of lytic genes.
  • Where are the regulatory genes located in relation to the lytic and lysogenic cycle genes?
    Regulatory genes are located between the lytic and lysogenic cycle genes on the bacteriophage's chromosome.
  • What is the function of the N protein in Lambda Bacteriophage regulation?
    N protein acts as an anti-terminator, allowing transcription to proceed past terminators and enabling expression of downstream genes.
  • How does the C2 protein influence the life cycle decision in Lambda Bacteriophage?
    C2 protein activates the PRE promoter, leading to production of CI and anti-Cro proteins, which promote the lysogenic cycle.
  • What happens when CI protein binds to operator regions?
    CI protein binds to operators and inhibits transcription of N and Cro, thereby promoting the lysogenic cycle.
  • How does high Cro protein concentration affect the Lambda Bacteriophage life cycle?
    High Cro protein binds to operators, inhibiting CI production and favoring the lytic cycle.
  • What role do environmental proteases play in Lambda Bacteriophage regulation?
    Environmental proteases degrade C2 protein; high protease activity reduces C2 levels, promoting the lytic cycle, while low activity allows C2 buildup, promoting the lysogenic cycle.
  • What is the first step in Lambda Bacteriophage gene regulation after infection?
    The first step is transcription of N and Cro genes, producing N and Cro proteins.
  • What is the effect of N protein binding to terminators?
    N protein binding to terminators allows transcription to continue past them, enabling expression of C2 and C3 proteins.
  • What does the C2 protein activate, and what is the result?
    C2 protein activates the PRE promoter, resulting in production of anti-Cro and CI proteins.
  • How does CI protein affect transcription of regulatory genes?
    CI protein binds to operator regions and blocks transcription of the regulatory region, ensuring only anti-Cro and CI are produced.
  • What happens to CI levels in the presence of high Cro protein?
    High Cro protein inhibits CI production by binding to operators, leading to activation of lytic cycle genes.
  • How do growth conditions determine the Lambda Bacteriophage life cycle?
    Good growth conditions increase protease activity, degrading C2 and favoring the lytic cycle; poor conditions decrease protease activity, allowing C2 buildup and promoting the lysogenic cycle.