Lecture12BIO115Winter11d2l

Lecture12BIO115Winter11d2l - BIO115 Viruses...

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BIO115 Viruses Dr. Jessica Pamment
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Characteristics of Viruses Not cellular; no plasma membrane, cytoplasm, or  ribosomes They don’t grow, they assemble All cell types can be infected, but viruses tend to  be species-specific They are small  They are obligate intracellular parasites
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T4 bacteriophage infecting an E. coli bacterium 0.5 µm
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Overview Why study viruses? The structure of viruses Viral reproduction Viruses as pathogens
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The Importance of Viruses Viruses as model systems to study  molecular mechanisms of gene regulation Viruses cause serious diseases in humans  and other organisms Viruses as tools in biotechnology
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Structure of Viruses Viruses are infectious particles consisting of  nucleic acid  enclosed in a  protein coat  (and  membranous envelope in some) Size range 20 - 300 nm Components: 1. Viral genome 2. Protein coat (and some have envelopes)
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Viral Genomes DNA viruses: double or single stranded DNA RNA viruses: double or single stranded RNA Genome is a single linear OR circular molecule Smallest virus has 4 genes Largest virus has several 100 to 1000 genes
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Capsids and Envelopes A capsid is a protein shell enclosing the  genome Capsids are shaped differently depending  on virus Membranous envelope surrounding some  capsids are derived from host cell
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Viral Structure RNA DNA 18 × 250 nm 70–90 nm (diameter) 80–200 nm (diameter) 80 × 225 nm RNA DNA 50 nm 50 nm 50 nm 20 nm (a) Tobacco mosaic virus (b) Adenoviruses (c) Influenza viruses (d) Bacteriophage T4
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Viral Reproductive Cycles Viruses can only reproduce in host cells Each type of virus can only infect its host range Viruses identify host cells by lock-and-key Entry into host cell can be by endocytosis or by  fusion with plasma membrane Some viruses inject nucleic acid into cell
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Bacteriophages infecting an Bacteriophages infecting an E. coli E. coli cell cell
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E. coli E. coli  O157:H7  O157:H7
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E. coli E. coli  O157:H7  O157:H7 E. coli  E. coli  inhabit the intestinal tracts of humans inhabit the intestinal tracts of humans The “O” and “H” antigens on their bodies and 
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This note was uploaded on 04/26/2011 for the course BIO 115 taught by Professor Pamment during the Winter '11 term at DePaul.

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Lecture12BIO115Winter11d2l - BIO115 Viruses...

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