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Viruses By Aaron Colby, Andrew Hack, and Chris Seward Table of Contents Structure Feeding Reproduction Species Viral Structure <½ m diameter Antigens Envelope DNA or RNA capsid Made from dead host cell membrane Not all viruses Capsid antigens Protects the virion’s contents Made of capsomeres envelope enzymes Enzymes DNA or RNA, Genome Controls growth, reproduction, etc. M A I N N E X T Viral Reproduction Entry: A virion attaches to a host cell. Absorption : The virion releases its DNA or RNA into the host cell. Reproduction: The viral DNA or RNA is injected into the host’s nucleus, starting the reproductive process Viral Reproduction: The Cell produces all the parts needed for many new virions Assembly: The new parts are assembled into new virons. Release: The new virons break free from the host cell either by breaking out, which destroys the cell or by pinching out which doesn’t. M A I N N E X T Viral Feeding Viruses do not feed because they are not living things. Viruses are only active when inside a host cell Viruses use host cell to produce more viruses M A I N N E X T Major Phyla & Viral Species There are many species of viruses. Icosahedral, Helical, Bacteriophage Viruses are categorized by physical features and host cells Nucleic Acid Capsid Shape Envelope Host Type Examples RNA Many-sided Absent Animal Poliovirus Present Animal AIDS virus Absent Plant Tobacco Mosaic Virus Present Animal Flu virus Absent Animal Cold viruses Present Animal Herpesviruses Rod Absent Bacteria Some bacterial viruses Complex Absent Bacteria Some bacterial viruses Present Animal Smallpox virus, chicken pox virus Rod DNA Many-Sided M A I N N E X T © 2002 Chris Seward, Aaron Colby, Andrew Hack - All Rights Reserved M A I N This slide show provides good information about viruses Remember that viruses are not made of cells and technically not considered to be living things