Distinguishing characteristics of viruses

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Distinguishing characteristics of viruses
Obligate intracellular parasites Extreme
genetic simplicity Contain DNA or RNA
Replication involves disassembly and reassembly
Replicate by "one-step growth
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Steps in replication Attachment Penetration
Uncoating (Transcription, Translation) Genome
replication Assembly Release
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Reasons to study viruses Cause infectious
diseases Some viruses cause cancer Provide
accessible experimental systems Virus-based
vectors
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Viruses differ from otherinfectious organisms in
their...
                                             
STRUCTURE,BIOLOGYand REPRODUCTION.
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ICOSAHEDRAL,
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Viruses have genetic materialwhich can be
either...
                                             
RNA        or        DNA.
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Viral genome strategies dsDNA (herpes, papova,
adeno, pox) ssDNA (parvo) dsRNA (reo,
rota) ssRNA () (picorna, toga, flavi,
corona) ssRNA (-) (rhabdo, paramyxo,
orthomyxo, bunya, filo) ssRNA (/-) (arena,
bunya) ssRNA (RTase) (retro, lenti)
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• Nucleic acid Strandedness Topology Sense Examples
• DNA Single-stranded Linear - Parvoviruses
• DNA Double-stranded Linear - Adenoviruses
• Herpesviruses
• Poxviruses
• DNA Double-stranded Circular - Papovaviruses
• RNA Single-stranded Linear Picornaviruses
• Togaviruses
• RNA Single-stranded Circular - Hepatitis delta
  virus
• Viroids
• RNA Single-stranded Linear - Rhabdoviruses
• Paramyxoviruses
• RNA Single-stranded Linear and - Orthomyxoviruses
• segmented Bunyaviruses
• RNA Single-stranded Linear and Ambi- Arenaviruses
• segmented sense
• RNA Double-stranded Linear and - Reoviruses
• segmented Rotaviruses

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This genetic material is...
                                             
packed into protein capsules calledCAPSIDS.
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they have a special moleculecalled a RECEPTORto
attach tothe cellular surface.
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After attachment the virusmay enter the cell by
aprocess called ENDOCYTOSISand then be released
intothe cytoplasm.
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NORMAL CELLS
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ABNORMAL CELLSThe cells become round and
enlargeand may eventually die whenthe new viral
particles are released
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The many viruses that infect man, ...
can be classified according tothe NUCLEIC ACID
present- either DNA or RNA.
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the herpes simplex virus gives rise to FEVER
BLISTERS and...
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the chickenpox virus resultsin SHINGLES.
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Infection may lead to the deathof the host e.g.
HIV infected individuals mostly die after8-10
years
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HEPATITIS B virus infection leads to chronic
hepatitis in 5-10 of infected patients and a
small percentage of these may eventually develop
primary liver cancer.
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get well after a period of sicknessto be immune
for the rest of their lives.Examples are
MEASLES INFECTION,RUBELLA or German
measles,MUMPS and many others...
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Virus-host cell interactions Productive Lethal
to the cell - typical lytic virus Not lethal to
the cell - transformation - persistence
Non-productive Lethal to the cell - apoptosis Not
lethal to the cell - transformation - latency
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Effects on host cell metabolism DNA
metabolism RNA metabolism Protein
metabolism Cellular and organismal
defenses Avoidance, public health
measures Immune system Anti-viral
drugs Interferon system