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Viruses Classified as Non-living, so why do we mention them in biology? Viruses From Latin for “poison” Segments of nucleic acid (DNA or RNA) contained in a protein coat (capsid); some also have an envelope Variety of shapes Very small, about 1/10 size of most bacteria NO cell membrane, nucleus, or organelles Influenza Virus Terms Pathogen = agents that cause disease, could be a virus, bacteria, fungus, or protist Vaccine = helps immune system recognize and destroy virus or bacteria Phage = another word for virus Viral Reproduction Lytic Cycle = cell is destroyed, ruptures (active stage) Lysogenic Cycle = cell survives; viral genes integrate into the host genes and divide with the host (dormant stage) Alone, viruses do not use energy. Viral Reproduction Diseases Caused by Viruses Bacteriophage = virus that infects bacteria (most common is T4); sometimes used to benefit patients by delivering missing genes (gene therapy) Plant viruses – tulip break virus, TMV (tobacco mosaic virus) Animal viruses – HIV, colds, Ebola, Hepatitis A, B, C, D, E; polio, herpes, influenza, mumps, rabies, SARS Cancer-causing viruses – HepBV & HepCV (cause liver CA), Epstein-Barr Virus (causes lymphoma); HPV (causes cervical CA) DNA vs. RNA Viruses DNA Viruses are stable and rarely mutate; this is why you only need to be vaccinated one time Ex. Chickenpox virus RNA Viruses are less stable and tend to mutate frequently; this is why a new flu shot comes out every year Ex. Influenza virus Which type is HIV?