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Human Virology Viruses are the most common cause of acute infections in humans What are viruses? http://www.youtube.com/watch?v=7O9JPyY44VA • Obligate intracellular parasites o They cannot perform metabolism on their own. • Viruses are simple Darwinian machines. They survive because they make huge amount of mutants. Selection removes the non-fittest. • Many viral diseases can be viewed as a failure of the virus to adapt to its host. The Origins of Virology • A hieroglyphic found in 3700 BC, Memphis ancient Egypt. Typical clinical signs of paralytic poliomyelitis • Ramesses V’s preserved mummy shows that he died of smallpox at about the age of 35 in 1143 BC. • The Chinese suffered from small pox in 1000 BC, China. They realized they can do something about it. Variolation. • 1519 A.D Smallpox was transferred from Europe to the Americas • The Year 1796. Edward Jenner vaccinated a boy against smallpox boy, with material from a cowpox lesion. • The Year 1892. Dmitri Iwanowski, showed that extracts from diseased tobacco plants can transmit disease to other plants by infectious agent smaller than a bacteria. • The 1918 Spanish Flu pandemic. 40-50 million deaths worldwide. What Virus Are Not? • They are NOT cellular organism. They are a bunch of chemicals, proteins, etc. • Outside a cell – are not considered to be alive. All cellular life has the following characteristics in common: • DNA • RNA • Making PROTEINS • SUPPLY OF ENERGY • REPRODUCE • CELL MEMBRANE • • REGULATION BASIC CHEMICALS Viruses versus cellular organisms Viruses Cells Metabolic capabilities No. totally depend on host ATP and most other compounds Extensive synthesis of ATP, vitamins lipids nucleic acid etc. Independent translation No, cannot make t/rRNA yes Hereditary material DNA or RNA; can be single or double stranded DNA; always double stranded. Expressed into t/r/mRNA Reproduction Assembly of preformed components Cell division Size Nano Meter Range Micro Meter Range http://www.cellsalive.com/howbig.htm