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Adenoviruses. Coloured transmission electron micrograph (TEM) of a group of adenoviruses, a cause of common cold-like infections. They contain DNA (deoxyribonucleic acid) genetic material which is surrounded by a protein coat (capsid, green). Adenovirus infections are common, particularly in children. The adenovirus may also be linked to the transformation of ordinary cells into cancerous ones. Viruses replicate by invading cells and inserting their DNA into the cell's genetic material so that it produces more viruses. Magnification: x90,000 at 6x7cm size. (KEYSTONE/SCIENCE PHOTO LIBRARY/EYE OF SCIENCE)