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VIRUSES (Are NOT living things (Do not grow, Do not have homeostasis…
VIRUSES
Are NOT living things
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Do not have homeostasis (ability to regulate physiological processes and maintain a stable equilibrium of internal conditions despite environmental changes)
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Contain DNA or RNA (as opposed to cells, which have DNA)
Structure = nucleic acid core, protein covering, and sometimes an envelope (vs cells with cytoplasm, cell membrane, cytoskeleton, and organelles for eukaryotic cells)
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History
1892, first pathogen discovered in tobacco plants
1931, electron microscope used to show first virus
1983, HIV retrovirus discovered
Bacteriophage
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Lytic cycle
- Attachment, 2. Phage DNA enters + destroys host DNA, 3. Synthesis of viral genomes and proteins, 4. Assembly, 5. Release
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Lysogenic cycle
- Attachment, 2. Penetration, 3. Phage DNA integration into host DNA, 4. Replication
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Viroids and Prions
Viroids
Consist of one strand of RNA, no capsid
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Prions
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Scrapie, which affects sheep
Bovine Spongiform Encephalopathy (mad cow disease) which affects cows and creates holes in the brain
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