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Bio171-F08-lec28 - Biology 171 Lecture 28 Friday November 7...

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Lecture 28: Friday, November 7, 2008 Biology 171 Today’s Topic: Viruses Announcements Next Week in Discussion: Pandemic Influenza Exam III, Monday, November 17 Covers Lectures 20-29 & Selection Simulations; Sexual Selection & Enteric Bacterial Flora discussions Text Reading Lec 28: 2 nd ed: Chapter 34 (780-800) 3 rd ed: Chapter 35 (769-789) Lec 29: 2 nd ed: Chapter 28 (607-634) 3 rd ed: Chapter 29 (593-623) Characteristics/Discovery of Viruses History of Smallpox Diversity of Viruses Lytic & Lysogenic Infections Influenza Retroviruses & HIV Genomic Impact of Retroviruses & Mobile Elements
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Viruses Viruses are tiny, non-cellular parasites that infect virtually every type of cell known. They cannot perform metabolism on their own —meaning outside a parasitized cell— and are not considered to be alive. Different types of viruses are specialized for infecting particular species and types of cells.
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Viruses are very small relative to eukaryotic or even bacterial cells ( Figure 35.5 ).
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Viruses are Ubiquitous in Natural Environments, Greatly Exceeding Cellular Life Forms in Abundance
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Lecture 28: Friday, November 7, 2008 Biology 171 Today’s Topic: Viruses Announcements Next Week in Discussion: Pandemic Influenza Exam III, Monday, November 17 Covers Lectures 20-29 & Selection Simulations; Sexual Selection & Enteric Bacterial Flora discussions Text Reading Lec 28: 2 nd ed: Chapter 34 (780-800) 3 rd ed: Chapter 35 (769-789) Lec 29: 2 nd ed: Chapter 28 (607-634) 3 rd ed: Chapter 29 (593-623) Characteristics/ Discovery of Viruses History of Smallpox Diversity of Viruses Lytic & Lysogenic Infections Influenza Retroviruses & HIV Genomic Impact of Retroviruses & Mobile Elements
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In 1892 a Russian scientist named Dmitri Ivanovsky was studying tobacco mosaic disease, which destroys the leaves of tobacco plants. The disease was clearly infectious; plants that came into contact with the sap from diseased plants were damaged as well. This ability to reproduce itself eliminated the possibility that the damaging agent might be a simple toxin. Ivanovsky ran an extract of diseased leaves through a very fine filter, with pores small enough to trap any known type of bacteria. But he found that whatever caused the disease went right through his filter. By the 1930s filters could finally be manufactured with pores tiny enough to prove that viruses are particulate after all, rather than being fluid in nature. The earliest electron microscopes also appeared in the 1930s, and viruses could at last be seen. Virus - “poisonous fluid”
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Lecture 28: Friday, November 7, 2008 Biology 171 Today’s Topic: Viruses Announcements Next Week in Discussion: Pandemic Influenza Exam III, Monday, November 17 Covers Lectures 20-29 & Selection Simulations; Sexual Selection & Enteric Bacterial Flora discussions Text Reading Lec 28: 2 nd ed: Chapter 34 (780-800) 3 rd ed: Chapter 35 (769-789) Lec 29: 2 nd ed: Chapter 28 (607-634) 3 rd ed: Chapter 29 (593-623) Characteristics/Discovery of Viruses History of Smallpox Diversity of Viruses Lytic & Lysogenic Infections Influenza Retroviruses & HIV Genomic Impact of Retroviruses & Mobile Elements
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Of all human infectious diseases, smallpox, caused by the Variola virus (below right), is believed to have resulted in more human deaths throughout history than from any other single pathogen.
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