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Animal Viruses

Animal Viruses. Because viruses are lifeless partials, their spread depends on other agents. A ( ) is an intermediate host that transfers a pathogen or parasite to another organism Classified as ( ) or ( ) viruses, ( ) or ( )-stranded

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Animal Viruses

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  1. Animal Viruses • Because viruses are lifeless partials, their spread depends on other agents. • A ( ) is an intermediate host that transfers a pathogen or parasite to another organism • Classified as ( ) or ( ) viruses, ( ) or ( )-stranded • Many have envelopes with glycoproteins that are specific for receptors. • The glycoproteins are made by the ER and added to the host cell’s membrane which envelopes the emerging viruses.

  2. Fig. 19-7 Capsid and viral genome enter the cell Capsid RNA HOST CELL Envelope (with glycoproteins) Viral genome (RNA) Template mRNA Capsid proteins ER Copy of genome (RNA) Glyco- proteins New virus

  3. Table 19-1a

  4. Table 19-1b

  5. RNA Viruses • The broadest variety of RNA genomes is found in viruses that infect animals • ( ) use ( ) to copy their RNA genome into DNA (HIV is ex.) • The viral DNA that is integrated into the host genome is called a ( ) • Unlike a prophage, a provirus remains a permanent resident of the host cell

  6. Fig. 19-8a Viral envelope Glycoprotein Capsid RNA (two identical strands) HOST CELL Reverse transcriptase HIV Reverse transcriptase Viral RNA RNA-DNA hybrid DNA NUCLEUS Provirus Chromosomal DNA RNA genome for the next viral generation mRNA New virus

  7. Fig. 19-8b Membrane of white blood cell HIV 0.25 µm HIV entering a cell New HIV leaving a cell

  8. Viral diseases in animals • Symptoms caused by - toxins - body’s defense mechanisms • ( ) – weakened or derivatives of viral particles capable of causing an immune response • ( ) not effective • Some antiviral medications interfere with viral ( ) synthesis

  9. Where do new viruses come from? • ( ) of existing viruses • The dissemination of an existing virus to a more widespread population • Or spread between species • ( ) – general outbreak of a disease • ( ) – global epidemic

  10. Fig. 19-9 (a) The 1918 flu pandemic 0.5 µm (b) Influenza A H5N1 virus (c) Vaccinating ducks

  11. Plant viruses • More than 2,000 types of viral diseases of plants are known and cause spots on leaves and fruits, stunted growth, and damaged flowers or roots • Most plant viruses have an RNA genome • Plant viral disease can spread by vertical transmission from parent plant or by horizontal transmission from an external source.

  12. Fig. 19-10

  13. Viroids and Prions: The Simplest Infectious Agents • ( )are circular RNA molecules that infect plants and disrupt their growth • ( ) are slow-acting, virtually indestructible infectious misfolded proteins that cause brain diseases in mammals • Prions propagate by converting normal proteins into the prion version • Scrapie in sheep, mad cow disease, and Creutzfeldt-Jakob disease in humans are all caused by prions

  14. Viroids in Plants

  15. Fig. 19-11 Misfolding of proteins to form prions Original prion Prion Aggregates of prions New prion Normal protein

  16. Scrapie in sheep

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