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VIRUS MEANS “POISON”! MADE OF PROTEIN AND NUCLEIC ACID (EITHER DNA or RNA) Protein part is the CAPSID NA is inside capsid Living or Not? They have genetic material & structural proteins BUT: No Ribosomes No Organelles No Nucleus Can’t Use Energy AND: They Cannot Reproduce on their own SO: They are NON-LIVING! They are referred to as Obligate Intracellular Parasites They need a HOST CELL in order to replicate. They can be classified 3 Ways: Polyhedron, Helical, Complex INTERESTING SHAPES! Some are “enveloped” with a membranelike structure Their nucleic acid type: Either DNA or RNA virus DNA virus:DNA is inserted into cell, then protein synthesis using virus mRNA Virus DNA joins host cell DNA and replicates with host cell DNA OR, RNA Virus: virus RNA is inserted into host cell,makes proteins directly OR, RNA retrovirus: DNA, made by reverse transcription, joins host DNA, followed by protein synthesis Classified by whether or not the virus is disease-causing Virus can be “virulent”--causes disease right away (like a cold or flu) If virulent, they undergo the LYTIC CYCLE Lytic Cycle: 1) Adsorption: virus attaches to host cell 2) Entry: virus NA is injected into host cell 3) Replication: Host cell starts making virus parts 4) Assembly: virus parts get put together 5) Release: host cell gets so full of new viruses that it bursts, releasing viruses Virus can be “temperate”--waits to cause disease later (like HIV) a) If temperate, virus goes into the LYSOGENIC CYCLE b) LYSOGENIC CYCLE: Starts like lytic cycle with adsorption & entry c) Then, Attachment: virus DNA joins with host DNA d) Replication: Host cell undergoes replication; virus DNA gets copied e) Activation: something triggers the virus to become virulent (lytic) Then,it starts the LYTIC CYCLE and causes infection (disease). How are viruses spread? Bodily fluids Through air, water Direct contact What is smaller than a virus? Viroid--NA only cause plant diseases Prion--small strand of amino acids; mammal diseases like CWD or Mad Cow disease How could you prevent viral infections? Vaccinations Wash hands! Cover your mouth when sneezing or coughing! Safe sex!