Transmission electron micrograph of virus particles of the papillomavirus, or wart virus, which belongs to the papovavirus class. Papilloma viruses cause warts to grow on the hands & feet as well as on the mucous membranes in the mouth, & on the genitals. Included in the papovavirus class are the polyoma viruses, which cause tumours in mice. Individual virions have icosahedral capsid symmetry (35-45nm across) & do not possess a lipoprotein envelope. Genetic information is in the form of double-stranded DNA contained within the protein capsid. Nearly all members of the group are oncogenic or capable of producing tumours. Magnification: x200,000 at 8x6 inch size.