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Published byViolet Robertson Modified over 8 years ago
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Ch 27.1 and 27.2 By: Dom Carter and Matt McKay
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Viruses Viruses aren’t cells Has a basic structure with a core nucleic acid surrounded by a protein Lacks a cytoplasm Viruses contain only a single nucleic acid, either DNA or RNA
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Structure of virions There are 4 structures, helical, icosahedral, binal, or polymorphic
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Viruses replicate by taking over host machinery A cell with a virus is often damaged by infection Viruses can reproduce only when they enter cells When viruses are outside the cell, viral particles are called virions and are metabocaly inert.
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Continued… Viruses lack ribosomes and the enzymes necessary for protein synthesis Viruses hijack the transcription and translation systems to produce the viral proteins from early genomes.
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Most viruses come in two simple shapes Most viruses are either helical or icosahedral Helical viruses have a rodlike or threadlike appearance Icosahedral have a soccer ball shape Icosahedron is a structure with 20 equilateral triangular facets
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Icosahedral virion Poliovirus has icosahedral symmetry
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