02 - picorna - notes.docx

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Molecular Genetics and Microbiology
Alan Cochrane

Positive strand RNA virusesPicornavirussmallRNAvirusRNA viruses Genome made of RNAMust encode own RNA dependent RNA polymeraseo These are very inaccurate enzymeso Allowing virus to rapidly mutate and evolve when met with changing conditionso Do not have exonuclease functionmake mistake cannot correct ito A viruas population often not of one single virus but a quasispecies where the population has multiple viruses that have different mutations but derived from same virus RNA virus genomes Some RNA virus families have dsRNA Most though have ssRNAReplication occurs through incoming genome transcribed into antigenome that is transcribed into genome ssRNA viruses For some ssRNA viruses the RNA can be immediately read as a mRNA by the cell ribosomes positive strand RNA viruseso Do not carry RdRp into the viriono EX Picornaviruses flaviviruses coronaviruses virus families Enteroviruses rhinoviruses hepatoviruses are members of the picornaviridae family For other ssRNA viruses the genome is complementary to the mRNA and is synthesized complementary RNA that direct protein synthesis Negative strand RNA virus 1 Poliovirus Unique to humans Three serotypes Transmitted via fecal oral routeo Human waste goes into land runoff sewage solid waste landfills then enter oceans rivers lakes groundwater irrigation water then into shellfish swimming water water supply crops watered with contaminated water aerosols from using humidifiers with contaminated waterand then into another individual Replicates in epithelial cells of gastrointestinal and upper respiratory tract Most infections asymptomaticAfter infection host has acquired immunity against reinfectionSymptomatic infectionso Called poliomyelitiso May cause neurological problemso From the GI tract the virus accesses the blood and then the central nervous systemo Motor neurons that control muscle are infected and destroyed causing paralysis of the dependent muscleso Paralysis of diaphragm would lead to suffocation so require iron lung for mechanical support of breathing Disappearance of polio with introduction of Salk and Sabin vaccines
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