MBIO 2020 Lecture Notes - Lecture 12: Veterinary Virology, Capsomere, Intracellular Parasite
10 Nov 2016
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Document Summary
Ivanowski - first systematic study of viruses - bacteria are not responsible for tobacco mosaic: used a filter to trap all bacteria, still had infectious agents. Beijernick - found that agent of tobacco mosaic - filterable viruses. F d"herrel - discovered bacteriophages - eaters of bacteria. Basic properties/criteria: acellular, dna or rna - never both. Small size: visible only with electron microscope. Viral chromosome: dna or rna - never both, ss or ds - never both, circular or linear, 3. 6 kb - 4 genes for ssrna - about 150kb - 100genes from ds dna. Viruses are essentially inert: lack ribosomes and almost all enzymes, use host component - ribosomes, energy, etc. Size - 20-400nm - smallest = ribosome largest =bacteria. Organization of capsid: the smallest protein unit - promoter - is usually a single polypeptide, promoters may aggregate into capsomers. Hexons - 6 identical promoters: sometimes promoter = capsomer, capsomers aggregate to form coat or capsid.
