Lecture 16 BILD1 S10

Lecture 16 BILD1 S10 - Announcements Final Exam Preparation...

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1 Announcements Final Exam Preparation PRACTICE FINAL EXAM posted on website EXTRA OFFICE HOURS this week (see website) REVIEW SESSION Wed. June 9th, 6:00-9:00 PM, Ledden Aud. 216 FINAL EXAM Fri. June 11th, 7:00-10:00 PM, TBA Lecture 15 Genome Evolution Microbial Systems: Viruses & Bacteria -“ model systems” reveal broad principles - unique systems in pathogenesis Figure 19.1 0.5 μ m E. coli bacterium Bacteriophage viruses 0.25 mm Virus Bacterium (prokaryote) nucleus Animal cell (eukaryote) - viral genome in protein coat - requires a host cell to reproduce (parasites)
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2 Discovery of Viruses Hypothesized in late 1800s, long before actually seen. Martinus Beijerinck (1800s) infectious agent in Fltered plant sap could reproduce Wendell Stanley (1935) crystallized infectious particle, identifying the virus TMV Tobacco Mosaic disease Structure of Viruses Very small infectious particles, consisting of: 1. nucleic acid genome (DNA or RNA) 2. protein coat 3. optional - membranous envelope Can take many forms, encoding from 4 to 100s of genes DNA Viruses Double-stranded DNA (dsDNA) Single-stranded DNA (ssDNA) RNA Viruses Double-stranded RNA (dsRNA) Single-stranded RNA (ssRNA) Viral genome duplicated and expressed using host proteins Structure of Viruses: 1. Viral Genomes ±igure 19.3 18 ´ 250 mm 70–90 nm (diameter) 20 nm 50 nm (a) Tobacco mosaic virus (b) Adenoviruses RNA DNA Capsomere Glycoprotein Capsomere protein Protein shell enclosing the viral genome, made from single to hundreds of proteins Structure of Viruses: 2. Viral Capsids
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3 Some viruses have membranous coverings, derived from the membrane of the host cell! Figure 19.3 InFuenza viruses RNA Glycoprotein Membranous envelope Capsid Structure of Viruses: 3. Viral Envelopes Viral Reproductive Cycles obligate intracellular parasites – can reproduce only within a host cell host cell factors replicate genome and make viral proteins speci±c host range – particular virus can infect limited host cell types largely determined by proteins for virus-cell recognition Viruses use host cell “machinery” VIRUS Capsid mRNA Viral DNA HOST CELL Viral DNA DNA Capsid ²igure 19.4 Entry into cell and uncoating of DNA Replication Transcription, Translation Self-assembly and exit of new viral particles Bacteriophages: viruses that infect bacteria ²igure 19.3 80 ´ 225 nm 50 nm (d) Bacteriophage T4 DNA Head Tail ±ber Tail sheath
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4 Phage Reproductive Cycles Phage is a dsDNA virus that infects bacteria Two alternative phage reproductive mechanisms: lytic cycle
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This note was uploaded on 10/16/2010 for the course BILD 1 taught by Professor Boulanger during the Spring '08 term at UCSD.

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Lecture 16 BILD1 S10 - Announcements Final Exam Preparation...

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