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19_Lecture_Post - Viruses Overview A Borrowed Life Viruses...

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Viruses Overview: A Borrowed Life Viruses called bacteriophages can infect and set in motion a genetic takeover of bacteria, such as Escherichia coli Viruses lead “a kind of borrowed life” between life - forms and chemicals The origins of molecular biology lie in early studies of viruses that infect bacteria
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The Discovery of Viruses: Scientific Inquiry Tobacco mosaic disease stunts growth of tobacco plants and gives their leaves a mosaic coloration In the late 1800s, researchers hypothesized that a particle smaller than bacteria caused the disease In 1935, Wendell Stanley confirmed this hypothesis by crystallizing the infectious particle, now known as tobacco mosaic virus (TMV)
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Figure 19.2 Extracted sap from tobacco plant with tobacco mosaic disease RESULTS Passed sap through a porcelain filter known to trap bacteria Healthy plants became infected Rubbed filtered sap on healthy tobacco plants 1 2 3 4
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Structure of Viruses Viruses are not cells A virus is a very small infectious particle consisting of nucleic acid enclosed in a protein coat and, in some cases, a membranous envelope Viral genomes may consist of either Double- or single-stranded DNA, or Double- or single-stranded RNA Depending on its type of nucleic acid, a virus is called a DNA virus or an RNA virus
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