Viruses are small infectious agents that depend on living cells of other organisms for replication. They are composed of either RNA or DNA genome, which is surrounded by a virus-coded protein coat called capsid. Different types of viral genome exist in the nature. It can contain single- or double-stranded DNA or RNA. In case of double-stranded RNA (ssRNA) viruses, positive-sense ssRNA can be transcribed to form messenger RNA (mRNA); in contrast, negative-sense ssRNA is complementary to mRNA. There are two categories of viruses based on general composition. Viruses formed from only a nucleic acid and capsid are called naked viruses or nonenveloped viruses. Viruses formed with a nucleic-acid packed capsid surrounded by a lipid layer are called enveloped viruses. The presentation will give better understanding on the topic.

Ridhi Kumari

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