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Published byBruno O’Neal’ Modified over 8 years ago
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What is a Virus? n Viruses are strands of DNA or RNA inside a protective coat. n They cannot live on their own, but invade cells in your body and use them as factories to make more viruses.
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What is a Virus? n This eventually kills the cell. n Diseases caused by the viruses includes colds, flu and AIDS.
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Properties of Viruses n Viruses continue to mystify scientists. n They are so small and simple, that they do not fit the living cell classification. n They range in size from 0.01µm to 0.3 µm in diameter. n Viruses have been found to produce diseases or genetic changes in animals, plants, algae, fungi, protozoa and bacterial cells.
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Properties of Viruses continued n Viruses have 5 properties that separate them from living cells: n 1. They have DNA or RNA - never both. n 2. Replication is controlled by the viral DNA in the host cell. n 3. They do not divide by binary fission or mitosis. n 4. Not capable of producing their own energy because they lack the required genes.
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Properties of Viruses continued n 5. They depend upon the ribosomes and nutrients of infected cells for protein production.
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Viral Structure Protective coat of fats and polysaccharides Protein Coat DNA or RNA not both
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Invasion of the Host Cell n This is a cyclic process. n 1. Virus contacts host cell. n 2. Virus or DNA enters host cell. n 3. Host cell DNA is broken up and new viral DNA or RNA is produced. n 4. Viruses use protein from host cell membranes to make new protein coats.
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Invasion of the Host Cell con’t. n 5. Viral enzymes are produced that lyse the host cells. n 6. Host cell membrane breaks. n 7. New viruses are released.
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Bacteriophages n These are viruses that invade bacterial cells. n Infective cycle is the same as previous description. n In some cases the viral and bacterial cell DNA join to form a complex. n The subsequent daughter cells will contain both DNA types.
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Bacteriophage Animation
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