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ch 27 1 and 27 2 n.
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Ch 27.1 and 27.2 PowerPoint Presentation
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Ch 27.1 and 27.2

Ch 27.1 and 27.2

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Ch 27.1 and 27.2

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  1. Ch 27.1 and 27.2 By: Dom Carter and Matt McKay

  2. 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

  3. Structure of virions • There are 4 structures, helical, icosahedral, binal, or polymorphic

  4. 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.

  5. 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.

  6. 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

  7. Icosahedral virion • Poliovirus has icosahedral symmetry