The envelope is derived from host lipid bilayers. The envelope usually contains spikes, glycoproteins that project from the surface of the envelope. Spikes function in attachment and entry to host cells. Made up of a protein, without nucleic acid. Prions cause mad cow disease, Scrapie, Creutsfeld-Jakob disease, and Kuru.
Icosahedral viruses have cubical symmetry.
For example, poliovirus Enveloped icosahedral viruses. For example, herpes simplex virus Enveloped helical viruses. Cultivation of animal viruses Viruses can only be grown in living cells. The following two methods are used to grow animal viruses. Tissue cultures are often set up as monolayers of cells in a Petri dish.