(c)  Enveloped symmetry

• •  In envelope viruses,nucleocapsid is surrounded by a lipid bilayer and glycoprotein derived from the modified host cell membrane called envelope.

•  Enveloped viruses are readily infectious agents if the envelope remains intact.

For example : Influenzavirus has enveloped symmetry

Fig. 14. Structure of Influenzavirus

 

4. Classification of Eukaryotic Viruses on the basis of Nucleic Acid

Major groups of viruses are distinguished on the basis of their nucleic acid content as:

• •  DNA Viruses

•  RNA Viruses

Subsequent subdivisions are based largely on other properties of nucleic acids. The RNA viruses can be ssRNA or dsRNA, although most are ssRNA.