Viruses Living a borrowed life
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Transcript of Viruses Living a borrowed life
VIRUSES
LIVING A BORROWED LIFE
DISCOVERY OF THE TOBACCO MOSAIC
VIRUS
• Small infectious agent that can only replicate inside the living cell of an organism
• Virus particles (virions)• Protein coat/capsid formed from
capsomeres
• Nucleic acid core (DNA/RNA) ~ 4-1000 genes
• Accessory structures*
• Lipid envelope – from membrane of the host cell
STRUCTURE AND PROPERTIES OF VIRUSES
TMV adenovirus influenza T4
VIRUS CLASSIFICATION http://3.bp.blogspot.com/_QUryhHJZKbU/S8uRMF8FD3I/AAAAAAAACI0/CINIMHP5Cmc/s320/Rhinotracheitis+Capsid.jpg
TYPES OF
ANIMAL VIRUSES
VIRUS REPRODUCTIVE CYCLES
Enveloped Virus
LYTIC VS LYSOGENIC CYCLES IN dsDNA BACTERIOPHAGES/ANIMAL VIRUSES
EXAMPLES• LYTIC VIRUSES• influenza• rhinovirus (common
cold)• LYSOGENIC VIRUSES• herpes I and II• some retroviruses
• MIXED STAGE VIRUSES
http://www.slic2.wsu.edu:82/hurlbert/micro101/images/vir5.gif
RNA virus replicationVirus RNA mRNA proteins
RNA retrovirus replicationVirus RNA DNA mRNA proteins
http://www.web-books.com/eLibrary/Books/B0/B22/MAIN/images/HIVcycle.gif
• Progressive theory
• Genetic material from cells escaped and mutated
• Regressive theory
• Evolved from bacteria that are obligate intracellular parasites
• Virus-First Hypothesis
• Evolved from the first RNA segments before the early cells
HYPOTHESES ON VIRAL ORIGINS
http://blogs.sciencemag.org/origins/WindowsLiveWriter/bc47e94c78c7_9B1A/mutation-v-genome_3.jpg
Viroids – RNA sequences that infect plants
BACTERIAL TRANSDUCTIONPhage-mediated DNA transfer
http://www.slic2.wsu.edu:82/hurlbert/micro101/pages/Chap9.html
http://liquidbio.pbworks.com/w/page/11135299/f/SwineEvolution.png, http://i2.squidoocdn.com/resize/squidoo_images/590/draft_lens4362032module30604592photo_1241127545geentic_makeup_of_flu.jpg
• pathogens
• viral gene therapy
• phage typing of bacteria
• source of enzymes
• pesticides
• antibacterial and anticancer agents
• molecular biology breakthroughs
• genetics and evolution
SIGNIFICANCE OF VIRUSES
http://en.wikipedia.org/wiki/File:LambdaPlaques.jpg