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VIRUSES Chapter 24 Video
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VIRAL STRUCTURE AND REPLICATION
Section 24.1
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Discovering Viruses: Late 1800’s –
Something very small is causing diseases! 1935 – It is not made of cells (living things). TMV Polio HIV
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What is a virus? A nonliving particle composed of a nucleic acid and a protein coat. Study of viruses = virology
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Why do we study them? Cause disease in living organisms
Useful tools for genetic research
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Are viruses living? NOPE! The Characteristic of life: growth
homeostasis metabolism organization cells reproduction Viral characteristics: NO YES within host cell NOPE!
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Common Diseases Caused by Viruses
AIDS Influenza Chickenpox Rabies Polio Mumps Colds
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Viral Structure All viruses have: Nucleic acid: (DNA or RNA)
Capsid: protein coat Some viruses have: Glycoprotein projections: signals Envelope: Bilipid membrane surrounding the capsid. Can fit “lock-and-key” with receptors on host cell.
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HIV
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Grouping viruses based upon…
SHAPE AND STRUCTURE: Envelope present or not? DNA or RNA? Single stranded or double stranded? How does it affect a human? Rabies Hepatitus Herpes
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Viral Size & Shape Size: Shape: 20 to 250 nm
Cannot be seen by a light microscope Shape: Determined by the genome (DNA) or capsid
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Some shapes: H1N1 or influenza Video
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Obligate Intracellular Parasites (huh?)
Viral Replication: Obligate Intracellular Parasites (huh?)
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Viral Replication in Eukaryotes
DNA viruses: DNA mRNA proteins Provirus: inserted viral DNA into host cell RNA viruses: mRNA protein Retroviruses: RNA DNA mRNA protein Reverse transcriptase: enzyme Example: HIV
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Viral Replication in Prokaryotes
Bacteriophage: virus that infects bacteria Helped scientists discover how viruses replicated Two replication cycles Lytic cycle: virulent Lysogenic cycle: temperate
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LYTIC CYCLE Animation
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LYSOGENIC CYCLE Animation
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Origin of Viruses Early viruses evolved from early cells
Viruses mutate quickly and frequently Thus they evolve quickly New strains formed this way
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Viral Disease Section 24.2 Flu Video
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Vectors An intermediate host that transfers pathogens from one organism to another Examples: Humans Animals mosquitoes Fleas ticks
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Chicken Pox & Shingles Virus: varicella-zoster herpesvirus
Symptoms: rash & fever Replication: Multiplies in lungs and uses blood network to reach skin Transmission: direct contact with skin rash
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Viral Hepatitis Virus: Hepatitis A, B, C, D, E Symptoms: Transmission:
Fever, nausea, jaundice, liver failure Transmission: Sexual contact (B,C,D) Fecal matter in food & water (A,E)
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AIDS Virus: HIV Transmission: through bodily tissues and fluids
retrovirus Transmission: through bodily tissues and fluids Symptoms: weakened immune system Treatment: Drugs target reverse transcriptase OR stop new capsids from forming (protease inhibitors).
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Viruses and Cancer Cancer: when cells divide at an uncontrolled rate and form a tumor Oncogenes: viral genes that cause cancer Examples: HPV cervical cancer Hepatitis B liver cancer Epstein-barr lymphoma
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Emerging Viruses New viruses are being discovered every year as humans alter ecosystems Examples: HIV Ebola SARS West Nile
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Preventions and Treatments
Vaccinations: to prevent disease Solution containing harmless version of virus Causes an immune response in the body Vector Control: Wildlife population control Drug Therapy: Interfere with viral nucleic acid
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2 types of Vaccines: Inactivated (killed)- virus particles
Attenuated (live)- weakened form of the virus Provide greater protection from disease Has lead to the eradication of some diseases ex) smallpox Common vaccines: measles, mumps, rubella, polio, hepatitis A & B, chickenpox
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How to protect yourself and others…
1. Wash your hands! 2. Don’t share tools (cups, toothbrushes) 3. Use protection when transmitting bodily fluids 4. Don’t become someone’s “Blood brother” 5. Avoid being bitten by any animal 6. Cover your mouth when sneezing
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Non-virus Disease Causers:
Viroids – a short singular strand of RNA smallest known particle to cause disease infects mostly plants Prions - protein particles without a genome mad cow disease
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Practice Graphing Problem
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