Virology
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	Spring, 2004 Lecture Outline 4/15 DNA PHAGE   Intro to dsDNA phage: large variety not closely related most have icosahedral or modified icosahedral heads some have tails of varying complexity most studied- E. coli phage: l [lambda] & T-even many other types of phage infecting E. coli & other bacteria Siphoviridae: prototype- l phage, temperate = lysogenic replication: covalent circularizaton of linear genome cohesive ends allows integration into host some bidirectional replication; most-sigma form rolling-circle concatamers cleaved at specific site assembly: precursor particle- prohead tails assemble separately Tectiviridae: [dsDNA grp] PRD 1 & PR 4: prototypes internal lipid layer; outer proteinaceous coat similar to pox & iridoviruses Myoviridae: T-even, prototype- T4 4-fold larger genome than l- 120 x 106 d circular permutation 1st discovered in this grp structure: elongated icosahedral head & contractile tail during assembly- process is very ordered head & tail are subassembled separately DNA organization- similar fxn genes grouped together very ordered activation- early; delayed early; quasi-late; late CRC Fig 93- good schematic of whole process of infection To kill or not to kill: to be latent or not??? bacteria have defense mechanism which phage must overcome different phage strategies temperate phage- lysogenic vs. virulent integrated- known as prophage vs. nonintegrated which exist as plasmids host benefits of temperate phage Next week: Viroids & prions- see Wagner, pp 304-5; CRC, ch 8; Cann- on reserve; & on-line Midterm 2- review as before; [-] strand RNA through DNA phage
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