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Transcript
Chapter 13 viruses Structure of viruses • • • • • Acellular Either have DNA or RNA Surrounded by a protein coat (capsid). Envelope – proteins, carbohydrates, lipids. Obligate intracellular parasites Complex virus complex Lytic cycle Lysogenized cell Lambda phage Biosynthesis maturation Daughter cells descendants Animal viruses • • • • • • • • Papillomavirus (DNA virus) Warts Common warts – legs, hands Direct contact Treated with interferon. Genital warts Finger-like projections (cauliflower) STD, cervical cancer uncoating RNA virus, poliovirus • Fecal – oral route – contaminated food, water • Multiplies in the throat and small intestine • CNS – multiplies in the nerve cells, paralysis • Polio vaccine RNA dependent RNA polymerase RNA as a template To make complementary strand of RNA Retrovirus • • • • • RNA – genetic material Reverse transcriptase RNA as a template to make DNA Capsid and envelope Human immunodeficiency virus (HIV) budding Latent viral infection • Herpes simplex virus • Dormant – nerve cells, activated under certain conditions – epithelial cells – cold sores • Herpes simplex virus 1 – oral herpes • Infancy - direct contact • Activated by fever, sunburn, stress Herpes Simplex Virus 2 • • • • Genital herpes Vesicles in the area Burning, difficulty walking acyclovir Viruses and cancer • • • • • Nucleated cells have proto-oncogenes Control (regulate) cell growth Code for proteins – regulate cell growth Mutation – abnormal proteins Loss of control – uncontrolled proliferation of the cell with mutation - cancer Mutations • • • • • • Chemicals UV light Viruses Epstein-Barr virus – DNA virus Dormant in some B lymphocytes Transmitted in saliva – infectious mononucleosis Epstein-Barr virus • • • • DNA virus Dormant in some B-lymphocytes Transmitted in saliva Infectious mononucleosis Burkitt’s Lymphoma • Common childhood cancer in Africa • Average age 7 – malaria is common • EBV and Plasmodium cause mutation in c-myc gene – proto-oncogene • Loss of control of cell growth • Uncontrolled proliferation • Leads to cancer – jaw bones Human T cell leukemia virus • • • • T cell leukemia – retrovirus Average age 45 Transmitted by sexual contact Mutation increases the production of the T cell growth factor. • Proliferation of T cells • Japan, Caribbean – multistep process Prions • Proteinaceous infectious particles – proteins • Scrapie – sheep • Scrape themselves against fences • Become paralyzed and die • Mad cow disease – bovine spongiform encephalopathy (BSE) – sponge like degeneration of the brain. • Shake, shiver Creutzfeldt –jakob disease • Occurs in certain families – hereditary • Transmitted by contaminated hamburgers • Dementia – die within a year viroids • • • • • Naked piece of RNA Plant pathogen Potato spindle tuber viroid Damage to potato plants Evolved from introns
