24 - Medical Virology Dept. of Medical Microbiology and...

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Unformatted text preview: Medical Virology Dept. of Medical Microbiology and Parasitology Shanghai Second Medical University Shanghai, China. E.mail: ( xkguo@shsmu.edu.cn ) General Virology Conception Viruses Virion Size and Shape Structure Replication Viral Variation Classification Conception Virology is the bioscience for study of viral nature,and the relationship between viruses and hosts. Viruses often cause serious diseases, relate to some cancers and congenital deformities, also can be used as tool for genetic engineering. 3000BC History Smallpox was endemic in China by 1000BC. In response, the practice of variolation was developed. Recognizing that survivors of smallpox outbreaks were protected from subsequent infection, variolation involved inhalation of the dried crusts from smallpox lesions like snuff, or in later modifications, inoculation of the pus from a lesion into a scratch on the forearm of a child. Definition of Virus Viruses may be defined as acellular organisms whose genomes consist of nucleic acid , and which obligately replicate inside host cells using host metabolic machinery and ribosomes to form a pool of components which assemble into particles called VIRIONS , which serve to protect the genome and to t ransfe r it to other cells Viral Properties Viruses are inert (nucleoprotein ) filterable Agents Viruses are obligate intracellular parasites Viruses cannot make energy or proteins independent of a host cell Viral genome are RNA or DNA but not both . Viruses have a naked capsid or envelope with attached proteins Viruses do not have the genetic capability to multiply by division. Viruses are non-living entities Consequences of Viral Properties Viruses are not living Viruses must be infectious to endure in nature Viruses must be able to use host cell processes to produce their components (viral messenger RNA, protein, and identical copies of the genome) Viruses must encode any required processes not provided by the cell Viral components must self-assemble Challenges the way we define life viruses do not respire, nor do they display irritability ; they do not move they do not grow they do most certainly reproduce, and may adapt to new hosts. Size and Shape Methods Size of Viruses Shapes of Viruses Methods of Analysis Electron microscopy : The resolution is 5nm (1nm = 10-9 m) X-ray crystallography Size of Viruses A small virus has a diameter of about 20nm. Parvovirus A large virus have a diameter of up to 400nm. Poxviruses Shape of Viruses Spherical Rod-shaped Brick-shaped Tadpole-shaped Bullet-shaped Filament Shapes of Viruses:Spherical Shapes of Viruses :Rod-shaped Shapes of Viruses :Brick-shaped . Tadpole-shaped Shapes of Viruses :Bullet-shaped Shapes of Viruses :Filament Structure of Viruses Virion the complete infectious unit of virus particle Structurally mature, extracellular virus particles. Virion Capsid Viral core envelope Viral core...
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This note was uploaded on 12/27/2011 for the course STEP 1 taught by Professor Dr.aslam during the Fall '11 term at Montgomery College.

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24 - Medical Virology Dept. of Medical Microbiology and...

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