BIO315 Molecular Biology
Dr. Henning Schneider
Study Guide T6
Lamda Phage and Major Shifts in Prokaryotic Gene Expression

1. Lytic reproduction of lambda phage

Concepts:

  1. Lambda phages enter a lysogenic or lytic reproduction phase.
  2. Antitermination initiaties the lytic phase of lamda phage reproduction.
  3. The lambda genome contains all genes that regulate phage reproduction and code for envelope proteins.

Study Questions:

  1. Explain the difference between a virulent and a temperate phage.
  2. Explain the difference between lytic and lysogenic mode of infection.
  3. Define the term prophage.
  4. In what forms can the phage genome occur?
  5. Which three gene classes are arranged sequentially of the phage DNA?
  6. Explain the pattern of gene expression during immediate early, delayed, and late transcription in lytic phages.
  7. Define the term sticky end.
  8. Describe the genetic map of the lambda phage genome including the organization of genes.
  9. Explain the function of the cro and cI gene products in lytic phages.
  10. Explain the concept of gene regulation through antitermination.
  11. Why are N and Q gene products called antiterminators?
  12. Explain the mechanism of N-directed antitermination.
  13. Explain the mechanism of Q-directed antitermination
  14. Which proteins interact with each other during processive antitermination?
  15. Explain how host (bacterial) genes cooperate with the transcription of phage genes during the lytic cycle.
  16. Explain the structural organization of the weak non-processive complex formed during antitermination.
  17. Explain the structural organization of the strong processive complex formed during antitermination.
  18. What is the function of individual molecules in the antitermination complex?
  19. Characterize the binding activities of the nut site.
  20. Characterize the role of NusA and N in the antitermination process.
2. Lysogenic reproduction of lambda phage
(including lytic/lysogenic phase switch)

Concepts:

  1. The lambda repressor establishes lysogenic reproduction cycle of lamda phages.
  2. The initation of lysogenic reproduction involves cro anti-sense RNA, cII protein and cI protein (lambda repressor).
  3. The levels of lambda prepressor protein (cI) is maintained by an autoregulation mechanisms.

Study Questions:

  1. Which are the key regulatory genes and proteins that determine whether phages enter the lysogenic or lytic phase?
  2. Explain the function of cro, cI and cIII in the regulation of the lysogenic phase.
  3. How does antisense cro RNA function to block the lytic cycle?
  4. Explain why high concentrations on cII protein turn on the lysogenic phase.
  5. Explain why high concentrations of cro protein turn on the lytic phase.
  6. Which promoters are involved in the initation of the lysigenic phase?
  7. Sketch the organization of the DNA including location of promoters and genes that are involved in the initiation of the lysogenic phase.
  8. Explain the footprint experiments that have been carried out to map the binding sites of cII.
  9. Why is cII also an activatior of the Prm promoter?
  10. Explain the difference between a weak and a strong promoter.
  11. How is the lysogenic phase maintained?
  12. Explain the autoregulaton mechanism that mainatins a steady-state of lambda repressor.
  13. What is the function of proteases in switching from lysogenic to lytic phase?
  14. Explain the induction of the lytic phase by recA protein.
  15. Which environmental changes can trigger major changes in gene transcription in prokaryotes.
  16. Which general types of regulatory "switch" mechanisms have evolved in bacteria and control major changes in gene expression?

Last modified on April 16, 2012 by HS.