Icosahedral viruses have triangular-shaped capsid and filamentous viruses have helical capsids.
Viruses show different structures depending upon the types of the capsid. Following are the differences between icosahedral and filamentous (helical) viruses:
|Icosahedral Viruses||Filamentous (helical) Viruses|
|Symmetry||They show radial symmetry.||They show helical symmetry.|
|Monomer arrangement||The pattern of subunits is triangular and the overall structure is rotationally symmetric.||Capsid monomers form helical tubes around the genome.|
|Length||The polyhedron has 20 triangular faces.||The length of the helical capsid extends up to 50 times its width.|
|Size||The capsid has a fixed size.||This varies in size to accommodate different lengths of nucleic acids.|
|Example||Poliovirus, rhinovirus, and adenovirus.||Influenza A virus, Soybean mosaic virus (SMV), and Tobacco mosaic virus (TMV).|