Lec37n - Viruses Bacteria Part I Viruses 6th Ed 328-331 333-335(Know Fig 18.6 7th Ed 334-337 339-341(Know Fig 18.8 8th Ed 381-384 387-388(Know Fig

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Viruses & Bacteria Part I: Viruses. 6 th Ed.: 328-331; 333-335 (Know Fig. 18.6). 7 th Ed.: 334-337; 339-341 (Know Fig. 18.8). 8 th Ed.: 381-384; 387-388 (Know Fig. 19.7). Part II: Exchange of genes to increase genetic diversity in bacteria. 6 th Ed. 340-344. 7 th Ed. 348- 351. 8 th Ed.: pp. 561-564 . These pages are NOT in your version of the text! Instead, they’re scanned in Course Documents on the Blackboard site. See “8 th edition pages on bacterial genetics”. ___________________________________________________ PART I: Viruses Viruses are infectious particles with a simple structure. They consist only of a nucleic acid genome, a small group of proteins, and sometimes a membrane envelope. (The word genome means the nucleic acid that stores genetic information for an organism; for us, the total of all our DNA). Most of the proteins are arranged into a capsid that surrounds and protects the genome. Individual proteins that make up the capsid are called capsomeres. Viruses can’t live independently; they must infect a host to reproduce. Viruses don’t have the energy sources, protein machinery, or raw materials needed to reproduce their genomes, direct synthesis of their proteins, or actually make the proteins. Instead, they rely completely on their host for these functions. Viruses turn infected host cells into factories that are dedicated to producing more virus particles, or virions. Different viruses infect animals, plants, and bacteria. We already saw an example of a bacteriophage (phage), or a virus that infects bacteria, in the Hershey-Chase experiment. They used the T2 phage to show that DNA is the genetic material. We saw that only the DNA genome was injected into the host cell: all the enzymes and macromolecule building blocks needed to make more virus particles, using the viral genome as a template, were provided by the bacterial cell. Viruses that infect animals and plants can he genomes can vary in several ways. First, their genomes can be either DNA or RNA, and can be single or double stranded (see examples in Table 18.1 (6 th + 7 th ) or 19.1 (8 th ), though you don’t have to know the specific viruses in the table.) Viruses can have a variety of shapes and structures. For instance, tobacco mosaic virus is rod shaped, with a coiled RNA genome surrounded by a capsid. Adenovirus, an animal virus that can cause colds and respiratory disease in people, also has a genome surrounded by a capsid. In this case, however, the genome is made of DNA, and the capsid surrounding it forms an icosahedron, with 20 faces. Glycoproteins, which will bind to the target cell, protrude from the capsid. We’ll examine the life cycle of influenza virus in detail, as an example.
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This note was uploaded on 09/23/2010 for the course BIO 202 taught by Professor Dean during the Fall '08 term at SUNY Stony Brook.

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Lec37n - Viruses Bacteria Part I Viruses 6th Ed 328-331 333-335(Know Fig 18.6 7th Ed 334-337 339-341(Know Fig 18.8 8th Ed 381-384 387-388(Know Fig

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