Bio Chapter 19

Bio Chapter 19 - Chapter 19: The Diversity of Viruses,...

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Chapter 19: The Diversity of Viruses, Prokaryotes, and Protists
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Viruses Characteristics of a virus: No cell membrane, no cytoplasm , no ribosomes- not a living thing Can only reproduce inside a host cell Very small size (0.05-0.2 micrometers) 2 major components constitute a virus : Single or double-stranded DNA or RNA Protein coat (may be surrounded by an envelope)
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Relative Sizes of Microorganisms
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Additional Viral Characteristics Viruses: Cannot grow or reproduce on their own Lack complex cellular organization Have a specialized protein coat Viral genetic material “hijacks” host cell to produce new viral components Viral components assemble rapidly into new viruses and burst from host cell Come in a variety of shapes…. .
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Viruses Are Host-Specific Each viral type specialized to attack specific host cell Ex: bacteria are infected by bacteriophage viruses Bacteriophages are actually a virus that specifically attacks bacterial cells
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Treating Diseases With Viruses Bacteriophages can treat bacterial diseases Rise in bacterial antibiotic resistance makes standard drugs less effective Bacteriophages specifically target host bacteria Bacteriophages are harmless to human body cells Bacteriophages Bacterial cell
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Viruses of Multicellular Organisms Are Specific Cold viruses attack membranes of respiratory tract Measles viruses infect the skin Rabies viruses attack nerve cells
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Viruses of Multicellular Organisms Are Specific Some viruses linked to cancer (i.e. leukemia, liver cancer, cervical cancer) Herpes virus attacks mucous membranes of mouth and lips Other herpes virus types cause genital sores HIV virus attacks specific white blood cell type, causing AIDS
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HIV virus
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Viral Infections Are Difficult to Treat Antibiotics are ineffective against viruses Antiviral drugs may also kill host cells Viruses “hide” within cells, are hard to detect Viruses have high mutation rates Mutations can create resistance to antiviral drugs Resistant viruses spread and multiply, rendering drugs ineffective
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Viruses as Biological Weapons Difficulty in treating viral infections makes viruses devastating weapons Limited smallpox stocks saved to develop future vaccine against unknown stocks Ebola hemorrhagic fever kills 90% of victims (no treatment or vaccine known)
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Viroids subcategory of viruses Viroids are infectious particles with only short RNA strands (no protein coat) Able to enter host cell nucleus and direct new viroid synthesis A number of crop diseases are caused by viroids i.e. cucumber disease, avocado sunblotch
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Prions The discovery of Kuru Fatal degenerative disease discovered in new guinea tribe (Fore) in 1950 Kuru causes loss of coordination, dementia, death Kuru in the Fore tribe was transmitted by ritual cannibalism of the dead
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Kuru Is Similar to Other Diseases Other diseases like Kuru include:
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This note was uploaded on 10/07/2011 for the course BIOL 1002 taught by Professor Pomarico during the Spring '08 term at LSU.

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Bio Chapter 19 - Chapter 19: The Diversity of Viruses,...

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