VIRUS

VIRUS

1. Classified based on host preferences

   • Animal viruses
   • Plant viruses
   • Bacterial viruses

2. Characteristics to divide viruses into taxonomic groups

   • Nature of host
   • Nucleic acid characteristics

3. Classification by International Committee for Taxonomy of Virus (ICTV) uses by:

   • Nucleic acid type
   • Nucleic acid strandedness
   • Type of host
   • The sense( +ve/-ve) of ssRNA
   • Presence/ absence of envelope

4. Name of the viruses:

   • viridae (family)
   • virinae (subfamily)
   • virus (genus and sp.)

5. Characteristics to divide viruses into taxonomic groups

   • Nature of host
   • Nucleic acid characteristics
     • ss or ds DNA
     • molecular weight of DNA or RNA
     • Segmentation
     • DNA or RNA
     • Sense of the strand

6. RNA Viruses

   • Picornaviruses
   • Togaviruses
   • Rhabdoviruses
   • Retroviruses
   • Multiplication occurs in cytoplasm
   • RNA-dependent RNA polymerases synthesizes as RNA
   • After maturation, viruses are released by budding or through ruptures in the host cell membrane

7. DNA viruses

   • Transcription and translation produce viral DNA and later capsid protein which synthesizes in the cytoplasm
   • DNA of the most viruses is released into the nucleus of the host cell
   • Adenoviruses, Herpesviruses, Papovaviruses abd Hepadnav viruses

8. How does bacteriophages multiply or replicate ?

   • Lytic cycle
     • Host cell lyse and die
     • Attachment, penetration, biosynthesis, maturation and release
   • Lysogenic cycle
     • Host cell remains alive

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