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Virus - Basics & News Taxonomy & Families What is a virus ? 1.Structure 2.Genome 3.Replication.

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Presentation on theme: "Virus - Basics & News Taxonomy & Families What is a virus ? 1.Structure 2.Genome 3.Replication."— Presentation transcript:

1 Virus - Basics & News Taxonomy & Families What is a virus ? 1.Structure 2.Genome 3.Replication

2 A virus is a virus (lat: poison) Replication: a replicating biochemical complex without its own metabolism requires metabolism of living host cell for replication Structure: Submicroscopic Size, 30 - 150 nm (exception:orthopox) Genome: contains genetic information, DNA or RNA

3 Virus - sizes

4 Comparison of Size: Virus/Bakterium

5 An infectious virus particle Virion The genome (DNA or RNA) is always packed in a protein structure the Capsid The combine Capsid/Genomestructure:Nukleocapsid The capsid structure can be spherical (Icosaeder) or helical structure (Tubulus) Some viruses have additional structures: a lipid envelope engulfing the capsid

6 Adenovirus: icosahedral capsid Tobacco mosaic virus: helical capsid non enveloped Virus: contains only nucleic acid and protein

7 enveloped viruses Herpes Simplex VirusParamyxovirus For enveloped viruses, the lipid envelope is always essential for infectivity. The envelops can be easily destoyed by ether & detergents

8 Spherical capsids have an icosahedral structure An Icosahedron has 20 triangular surfaces and three axes of symmetry Picornavirus: 5-fold axes of smmetry animated X-Ray structure

9 Icosahedral capsids are built from capsomers: identical units of the same proteins X-Ray structure capsid of picornaviridae

10 The capsid surface of non enveloped viruse must carry structures for binding to cellular receptors Canyons for binding to CAR (many enterovirus types) Fiber (Spikes) for binding to CAR (many adenovirus types) These both (non related) viruses bind to CAR but the binding structures look very different

11 Comparison: replication of virus vs. bacterium obligat intrazellulär NIE auf Nährmedien, Agars usw. lebende Zellen erforderlich: Versuchstier Brutei Zellkultur Eklipse bzw. Latenzperiode, Adsorption, Penetration, Uncoating Proteinsynthese & Genomreplikation Assembly & Virusfreisetzung

12 Classical Concept of ICTV taxonomy system: family/genus/species family names:...-idae relevant for virus family: –genome type (DNA, RNA; ds-, ss-, ) –capsid structure (helical, icosahedral) –enveloped/non enveloped

13 RNA-Virus RNA viruses

14

15 DNA viruses DNA-Virus

16 Baltimore System way of mRNA production (->Proteinsynthesis) DNA Virus RNA Virus


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