Virus+Prokaryotes (21)

Virus+Prokaryotes (21) - Viruses, Bacteria and Archaea...

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Viruses, Bacteria and Archaea Viruses, Bacteria and Archaea Human influenza viruses Escherichia coli Archaea
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Viruses Noncellular and thus cannot be classified with cellular organisms Generally smaller than 200 nm in diameter Each type has at least two parts Capsid: outer layer composed of protein subunits Some enveloped by membrane; others “naked” Nucleic acid core: DNA or RNA (several hundred genes) Vary in shape from thead-like to polyhedral
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Categorization Categorization Viruses: Are obligate intracellular parasites Cannot reproduce outside a living cell Can be cultured only inside living cells Cannot metabolize or respond to stimuli Evolve as a result of mutation and natural selection Are very specific All are infectious! Classification is based on: Type of nucleic acid (DNA/RNA;single or double stranded) Size and shape Presence / absence of outer envelope
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Bacteriophages Portions of capsid adhere to specific receptor on the host cell Not easily recognized by host immune system Viral nucleic acid enters the cell Once inside, the virus takes over metabolic machinery of the host cell Viral Replication Viral Replication Lytic Cycle Lysogenic Cycle
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Reproduction of Animal Virus Reproduction of Animal Virus Animal virus enters the host cell Uncoating releases viral DNA or RNA Budding: Viral particles released in a bud Acquires a membranous envelope Retroviruses (AIDS) Contain reverse transcriptase Carries out RNA cDNA reverse transcription cDNA becomes integrated into host DNA
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Virus+Prokaryotes (21) - Viruses, Bacteria and Archaea...

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