20 BISC 120_Chapter 19 VIRUSES POST

20 BISC 120_Chapter 19 VIRUSES POST - 10/8/2010 Fig. 19-1...

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10/8/2010 1 Chapter 19 VIRUSES Mobile genetic elements Fig. 19-1 0.5 μm Viruses • Infectious particles consisting of nucleic acid enclosed in protein coat & sometimes a membranous envelope • Obligate intracellular parasites • Use genetics to take over of a cell But are they alive? Viruses: Are they alive? A debated issue • Employ DNA or RNA (single or double stranded) • Contain proteins • Reproduce but not without use of host cells’ genetic machinery One virus may produce protein coated tails without host • Evolve in response to their environment (influenza, H5N1avian , H1N1swine) • Some can be crystallized! “A borrowed life”
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10/8/2010 2 What is Biology? Study of living organisms descended from single-celled ancestor that evolved 4 billion years ago Living organism consists of one or more cells Contains genetic information Uses genetic info to reproduce themselves Can convert molecules from environment into new biological molecules Can extract energy from environment and use it to do biological work Can regulate their internal environment Discovery international science • Adolf Mayer (1883) & Tobacco mosaic disease • Transmit disease from plant to plant leaf • Dimitri Ivanowsky (1890) filtered sap infectious • Maritinus Beijerinck (1898) demonstrated infectious agent could reproduce • Wendell Stanley (1935) crystallized infectious particle: TMV Fig. 19-2 RESULTS 1 2 3 Extracted sap from tobacco plant with tobacco mosaic disease Passed sap through a porcelain filter known to trap bacteria Rubbed filtered sap on healthy tobacco plants 4 Healthy plants became infected Fig. 19-3a (a) Tobacco mosaic virus 20 nm 18 250 nm Capsomere of capsid RNA
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This note was uploaded on 10/29/2010 for the course BISC 13004 taught by Professor Wetzer during the Fall '09 term at USC.

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20 BISC 120_Chapter 19 VIRUSES POST - 10/8/2010 Fig. 19-1...

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