viruses - Read the history Emerging Viruses: - Many are due...

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Read the history Emerging Viruses: - Many are due to Demographic changes, travel, commerce, ecological changes, viral mutations, environmental changes (T. 10.4) Characteristics: (Fig. 10.1) Acellular infectious agents. Obligate intracellular parasites. Reproduce within host cell. Core - nucleic acid DNA or RNA, single or double stranded Capsid - protein coat made of subunits (capsomeres) Envelope - lipid bilayer membrane derived from host cell membrane Spikes - glycoproteins attach virus to cell receptors Variety of size and shapes (Fig. 10.2) Specificity: Infect specific tissues or species (cell receptors, enzymes for replication) Origin of viruses Classification: in different ways 1. Host infeccted: bacteriophages, plant viruses, animal viruses 2. Type of host structure infected: Dermotropic - skin Neurotropic - nervous tissue Viscerotropic - digestive system Pneumortopic - respiratory system 3. Genome structure: RNA or DNA, single stranded or double stranded Virus particle structure (capsid shape) Presence or absence of viral envelope Family and species (T. 10.1, 10.2) p. 278-283 Important groups Nucleic acid classification: RNA: ssRNA or dsRNA two types of ssRNA: Positive (+) sense RNA - RNA acts like mRNA, is transcribed by hosts's ribosomes Negative (-) sense RNA - RNA acts as a template during transcription to make complementary (+) sense mRNA which is translated by hosts's ribosomes (-) sense RNA viruses carry RNA polymerase for transcription. RNA animal viruses classified according to their nucleic acid content, capsid shape and presence or absence of envelope, (+) or (-) sense RNA (T. 10.1, Fig. 10.3) DNA viruses can be dsDNA or ssDNA DNA animal viruses are grouped according to DNA organization dsDNA viruses classified according to DNA shape, capsid shape, presence or absence of envelope (T. 10.2, fig. 10.5) 4. Group disease causing viruses according to route of transmission: Enteric viruses - ingested (contamination) fecal-oral route Respiratory viruses - inhaled, replicate in respiratory tract Viral zoonoses - zoonotic viruses, transmitted from animal to human
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Arboviruses - transmitted by bite of infected arthropod (arthropod borne) Sexually transmitted viruses Viral Replication: Replication cycle: produce more viruses 1. Adsorption -attach to host cell 2. Penetration - virion entry in host cell 3. Synthesis - virus nucleic acid and capsid proteins using host's resources Maturation - assembly of virion Release - exit host cell Bacteriophage Replication Read history Characteristics - (T. 10.5, Fig. 10.10) T4 - obligate parasite of E. coli dsDNA Capsid: Head -contain DNA Collar, tail sheath - allows genome to enter cell Plate, tail fibers - attach to receptors on host cell T4 replication (virulent) Lytic cycle (Fig. 10.11) Adsorption - tail fibers attach to specific receptors on host cell Penetration - genome enters host cell Synthesis - host cell is used to make viral DNA and proteins Maturation - assembly of viral particle Release.- lysozyme break cell wall, phages released
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This note was uploaded on 04/08/2008 for the course BI 151 taught by Professor Zavras during the Spring '08 term at Fairfield.

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viruses - Read the history Emerging Viruses: - Many are due...

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