Thus viral capsids consist of repeating subunits of the same protein. This implies a very efficient structure, subunit proteins have a tendency to bind to each other, and thus the information for morphogenesis lies in the amino acid structure of the virus. Viruses that do not form rods are all spherical. There seems to be no ellipsoid viruses. In good electron micrographs the spheres are polyhedrons.
Viruses form crystals very easily suggesting an ordered structure.
All known viruses consist of two components, proteins and nucleic acids. All evidence indicates that the proteins are on the outside and that the NA is internal. The virus appears to consist of a number of identical subunits arranged around the NA . Thus virus particles could form spontaneously from purified subunits without any extraneous material. The forces, which drive self-assembly, are hydrophobic and electrostatic interactions, only rarely are covalent bonds involved in virus assembly.