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Viruses

Viruses. Virus - means “poison ” Compared to bacteria, viruses are microscopic! Characteristics Core of DNA or RNA and a protein coat can only reproduce by infecting living cells. highly specific to host a. ex: plant viruses only infect plants. Structure.

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Viruses

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  1. Viruses Virus - means “poison” Compared to bacteria, viruses are microscopic! Characteristics Core of DNA or RNA and a protein coat can only reproduce by infecting living cells. highly specific to host a. ex: plant viruses only infect plants

  2. Structure • capsid: outer protein coat • core: DNA or RNA

  3. Modes of Infection(how they infect you) • LyticInfection – see page 484 • virus enter cell, makes copies, causes cell to burst or “lyse” • ex: cold, flu (influenza)

  4. Lysogenic Infection – see page 485 • a. virus enters cell, embeds its DNA in the DNA of the host cell (called a prophage), and is replicated along with the host cells DNA. It waits!!! • ex: cold sore, herpes

  5. Viruses and Disease • 1. Diseases caused by viruses • a. polio, measles, AIDS, mumps, flu, yellow fever, rabies, common cold • b. cannot cure a virus, can only treat symptoms • c. some viruses can cause cancer – called “oncogenic viruses”

  6. 2. vaccines: part of weakened or killed virus injected into body to build immunity. 3. bacteriophage: virus that infects bacteria. • 4. retroviruses (ex: HIV) work backwards and produce a DNA copy of their RNA • 5. prions: “protein infectious particles” - contain protein, but no DNA or RNA (ex: mad cow disease)

  7. Are they alive? • Characteristics of Life Viruses • 1. organized organized • 2. reproduce reproduces only inside a living cell • 3. grows no growth • 4. responds no response • 5. adapts to environment adapts to environment • 6. needs energy does not need energy • 7. composed of cell/s no cells

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