BIOL 2100 Chapter Notes - Chapter 19: Tobacco Mosaic Virus, Lytic Cycle, Viral Disease
25 Nov 2016
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Tobacco mosaic disease can be transmitted by contact with sap from a diseased plant. Even after the sap from diseased plants was passed through a filter that removes bacteria, the filtered sap still had the disease. The pathogen only replicated within the host it infected. The cause of the mosaic disease could not be cultivated on nutrient medium. Viruses range from being smaller than a ribosome, to being barely visible in a light microscope. Viruses can be crystallized, meaning that they are not cells. The structure of a virus = an infectious particle with protein coat enclosing nucleic acid, and occasionally surrounded by a membranous envelope. Viruses can have genomes of either double-stranded or single-stranded rna or dna. Capsid = protein shell that encloses the nucleic acid. Viral envelopes = derived from the membrane of host cells. Bacteriophages/phages = elongated icosahedral heads with a protein tail of fibers. Viruses lack metabolic enzymes and mechanisms for making proteins.
