lecture_17__05 - What is a virus? A parasitic genome...

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What is a virus? A parasitic genome (either RNA or DNA), enclosed in a protective protein capsule, that is unable to reproduce without a "host" cell Fig. 18.2
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Fig. 18.3 Most viruses use the host cell's resources to replicate themselves. These include DNA polymerases, RNA polymerases, all of the protein translation machinery, and all of the components that are necessary to make nucleic acids and proteins. Release of new virus particles from an infected cell usually is accompanied by destruction of the host cell
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Bacteriophage T4 infection of E. coli: Fig. 18.4
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Bacteriophage λ lytic cycle vs. lysogenic cycle: Fig. 18.5
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viral genome : double-stranded DNA txn mRNA RNA polymerase poxvirus (smallpox, vaccinia), herpesvirus (simplex I, II, chicken pox, shingles, Epstein-Barr) single-stranded DNA txn DNA polymerase mRNA RNA polymerase parvovirus; requires DNA replication to occur in host cell, often requires helper virus single-stranded RNA: template for reverse transcriptase txn mRNA reverse transcriptase DNA polymerase RNA polymerase Retroviruses : RNA tumor viruses, HIV (AIDS)
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single-stranded RNA: template (non-coding) strand, "anti-sense" transcriptase mRNA Rhabdovirus (rabies); Paramyxovirus (measles, mumps); Orthomyxovirus (influenza). Virus must carry RNA transcriptase enzyme in viral particle single-stranded RNA: non-template (coding) strand, "sense" mRNA Picornavirus (polio, cold viruses), Togavirus (rubella, yellow fever). Transcriptase necessary for viral replication but can be encoded in viral genome double-stranded RNA mRNA RNA-dependent RNA polymerase Reovirus ( endemic/epidemic gastroenteritis and infantile diarrhoea). RNA- dependent RNA polymerase present in viral particle viral genome, continued :
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transcription vs. replication of RNA virus genomes
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lecture_17__05 - What is a virus? A parasitic genome...

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