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MCB 229 Spring 2000 Study Guide 16 Prof. Terry
Covers Lecture for April 6

This study guide is intended for you to use while you are doing the assigned text reading. Quiz questions will be made with reference to topics in this study guide. Quiz #16, based on questions from this study guide, must be completed by midnight before the class on Thursday, April 6. You will need to create your "myWebCT" account and visit the MCB 229 WebCT page in order to access this quiz.

Chapter 16. Viruses: general principles.
  1. Who deserves credit for discovering the principle of immunization against viral disease: Lady Wortley Montagu or Edward Jenner?
  2. What is a virus? How does a virus differ from a virion? What biomolecules are found in virions?
  3. What assay systems are commonly used to study animal viruses? What components must be added to a petri plate to view phage plaques? What assay systems are used to study plant viruses?
  4. Skim the section on "Viruse Purification and assays", pp. 339-341.
  5. How can the concentration of viruses in a sample be counted by direct or indirect methods? What is meant by PFU? Does this measure the number of virus particles in a sample? Why or why not?
  6. The section "The Structure of Viruses" (pp. 342-352) has lots of detail and many photographs. I don't expect you to remember all these details, except as noted below. Do read figure captions as you look at the figures, though.
  7. What do the following terms mean? Capsid, nucleocapsid, icosahedron, protomer, spikes? What are the common shapes of virions? What do the terms "enveloped virus" and "complex virus" imply?
  8. What type(s) of nucleic acid are found in virions? How many strands are present? Do any virions contain both DNA and RNA? What is meant by "+" and "-" RNA? Are viral nucleic acids linear or circular? Is it possible for a linear viral chromosome to become circularized? If so, how?
  9. What is meant by a "segmented genome"? Are there any viruses in which individual virions are insufficient to cause infection? If so, how many virions are needed? Why?
  10. Read box 16.2, "The origin of viruses". What are the two major speculations about viral origins?
  11. How does the classification of viruses compare to the classification of bacteria (remember Bergey's manual?) What characters are used in classifying viruses?
Chapter 17. Bacteriophages.
  1. What is meant by a lytic cycle? How does this cycle end?
  2. What is "one-step growth experiment"? What is meant by the terms: latent period, eclipse, burst size, rise period?
  3. What sorts of materials serve as receptors for phages?
  4. We will concentrate on the study of 3 E. coli phages (aka coliphages) to demonstrate the variety of mechanisms involved: T4, MS2, and Lambda.
  5. Phage T4: Examine Figs. 17.5-7 and related text. Note that phages T2, 4 and 6 (T-even phages) are very similar. How does T4 attach to host cells? How does the DNA enter? Which enzymes are "early enzymes? How do they differ from "late" enzymes and other proteins? Are early and late genes encoded on the same strand of DNA? What do restiction enzymes do (see pp. 311—312 and Fig. 15.2)? How does phage T4 avoid damage by restiction enzymes? What are concatemers, and how are they involved in T4 DNA replication? How does the promoter for late T4 genes differ from the early promoter? How are new T4 virions assembled? What is a typical burst size for T4? When and how does the host cell lyse?
  6. Phage MS2: What is the nucleic acid for this phage? How many enzymes are encoded? Is the virion RNA + or -? What enzyme is needed to replicate copies of this phage nucleic acid? How does MS2 attach to host cells?
  7. Phage Lambda: What form of nucleic acid is in the virion? Does the virion contain linear or circular nucleic acid? What happens to this NA when it enters the cell? Note that lambda can undergo either a lytic or a lysogenic stage, depending on early events following infection. What is meant by the following terms: lysogeny, temperate phage; prophage; induction; lysogenic conversion? What environmental conditions favor lysogeny over lytic infection?
  8. Early events in the lambda phage life cycle that determine whether lytic or lysogenic modes will be active are complex, and are described on pp. 367-369 and Fig. 17.18. Note that there is a race between two proteins: cro protein and lambda repressor. What does each of these proteins do? What is the function of the integrase enzyme? What situations can trigger induction?