Classification of viruses

Classification of viruses

Viruses are categorized into families and groups according to many different factors , such as the nucleic acid type , replication process , envelop and capsid structure.

classification of the virus according to basic host:

  • plant viruses
  • animal viruses
  • human viruses
  • prokaryotic viruses

Classification of the virus according to genetic material:

  • Ribonucleic acid (RNA)
  • Deoxyribonucleic acid (DNA)

DNA and RNA viruses are divided into double stranded (Ds) and single stranded (Ss), So the classification according to genetic material become:

  • Ss DNA
  • Ds DNA
  • Ss RNA
  • Ds RNA

Ss RNA viruses are divided into positive polarity ( positive sense) and negative polarity ( negative sense) , So the classification according to genetic material become:

  • Ss DNA
  • Ds DNA
  • Ds RNA
  • Ss RNA positive sense
  • Ss RNA negative sense

Positive sense: means RNA acts like mRNA and goes to ribosomes to be directly translated.
Negative sense: not like mRNA and thus cannot undergo translation, it must be transcribed into a positive strand to give a complementary strand to mRNA and this complementary strand undergoes translation.

genetic material have different shapes so it’s classified into :

  • linear
  • circular
  • segmented

Classification of the virus according to capsid:

Capsid is the structural protein which surrounds the genetic material.

  • Icosahedral shape (Cubic)
  • Helical shape (filamentous)
  • Complex (Head-tail)

Classification of the virus according to envelope:

Some viruses also have envelope usually consisting of lipid bi layer that carry the capsid in the genetic material , but some viruses don’t have it they only have the capsid itself.

  • enveloped viruses
  • non-enveloped viruses (Naked Viruses)

What does the envelope do for the virus?
 It Protects genome during passage from one cell to another.
 It Aid in entry process of the virus into the target cell.
 It Package enzymes for early steps of infection.

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