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AN INTRODUCTION TO THE VIRUS

AN INTRODUCTION TO THE VIRUS. LIVING OR NON-LIVING. NO, because… Acellular Lack both DNA & RNA Not reproduce on own Must be inside host cell Not make/store cellular energy (ATP) Not grow Can mutate. VIRAL STRUCTURES. Genome Single or double strand either DNA or RNA Capsid

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AN INTRODUCTION TO THE VIRUS

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  1. AN INTRODUCTION TOTHE VIRUS

  2. LIVING OR NON-LIVING NO, because… • Acellular • Lack both DNA & RNA • Not reproduce on own • Must be inside host cell • Not make/store cellular energy (ATP) • Not grow • Can mutate

  3. VIRAL STRUCTURES • Genome • Single or double strand either DNA or RNA • Capsid • Protein coat surrounds genome • Gives shape • Envelope • Outer protective coat • Helps hide

  4. VIRAL STRUCTURE • Classified according to shape of capsid • Polyhedral: triangular faces • Helical: coiled spring • Complex: bacteriophage

  5. VIRAL REPRODUCTION LYTIC CYCLE LYSOGENIC CYCLE Attachment Entry Formation of Prophage Joining of host & viral DNA Replication – new gene replicated every time cell goes through mitosis Result: Become permanent part DNA External trigger cause virus activate • Attachment • Entry – either entire virus or genetic material injected • Replication – viral DNA takes control host cell • Assembly – cell used make new viruses • Release – cell breaks open

  6. VIRAL CLASSIFICATION • Virulent • Deadly • Evade host’s defenses • Rabies, flu • lytic • Temperate • Not cause immediate disease or death • Remain dormant • Lysogenic • HIV, HPV • Provirus • Remain dormant in host & reoccur multiple times • Herpes • Retrovirus • Contains RNA • Works backwards • RNA  DNA • HIV

  7. VIRAL DISCOVERY Research on Tobacco Plant Diseases • Mayer • Show contagious (spread thru plant juices) • Proposed caused small bacteria • Ivanowsky • Thru use filtration techniques on sap – proved disease caused something smaller than bacteria • Beijerinck • Shows pathogen only reproduce w/in plant (not grow in culture) • Unable to be killed by ethanol • Rejected bacteria theory & came up with the term “virus”

  8. VIRAL DISCOVERY • Stanley • First see & crystallize virus known as Tobacco Mosaic Virus • Due to electron microscopy technology

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