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Unformatted text preview: Chapter 18: Viruses 8/29/06 1:30 PM Viruses are thought to come after the first cells Lockandkey mechanism when virus attacks a host Between the viral proteins and receptor cells of host Know basics of viral reproduction Lytic cycle: virus kills cell after reproducing Temperate phages: a group of phages that can be either lycogenic or lytic Envelope reproductive cycle Retroviruses: most complex viruses Most recent viruses HIV/AIDS Ebola and Lassa virus oCarried by monkeys West Nile virus oAffects people in different ways SARS oRespiratory infection Bird flu Hantavirus oCarried by mice, rats Genes are continually mutating so viruses are constantly changing. At least 2,000 viruses have been identified in plants They are mostly RNA viruses Infecting agents Viroids oSmallest of all infecting agents Chapter 18: Viruses 8/29/06 1:30 PM oAffect plants, in particular Prions oVery simple infective proteins oAttaches to proteins oCauses madcow disease o Bacteria Consists of circular DNA Contains a dense concentration of DNA called the nucleoid area A series of little circles of DNA called plasmoids Reproduce through binary fission Three Gene Transfer Transformation: uptake of foreign DNA Transduction oBacteria phages carry genetic material Conjucation oGenetic sexDirect transmission R plamids Small DNA rings that have genes that code for enzymes that kill antibiotics Insertion sequence: a single gene moves from location to another position on the DNA strand oResults in a different type of bacteria with different resistance Transposon: a longer piece of of the DNA strand moves to a different place on the strand READ ABOUT OPERONS ...
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