virus biology life cycles

Category: Education

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virus biology life cycles


By: Jadli (116 month(s) ago)

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Presentation Transcript

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Virus Replication

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Virus: A biological particle composed of nucleic acid and protein Intracellular Parasites: organism that must “live” inside a host What is a Virus?

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Is Fire Alive? 1) Made of cells? 2) Organization? 3) Require energy? 4) Respond to Environment? 5) Grow? 6) Reproduce? 7) Adapt? yes yes yes yes no no no

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Reproduce They have DNA or RNA They can adapt to surroundings The have organization They are not made of cells or organelles They cannot reproduce without a host They don’t have both DNA and RNA They do not metabolize energy Yes No Are Viruses Alive?

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All Have: 1) Capsid: coat of protein that surrounds DNA or RNA 2) Nucleic Acid: RNA or DNA Some Have: Tail Fibers: Used for attachment (not legs) Shapes vary Virus Parts

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Cannot reproduce w/o a host cell Virulent: cause disease Bacteriophages (infect bacteria) are often studied Replication is similar with many animal viruses Viral Replication

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1st Step: Attachment Virus lands on cell membrane Virus attaches to a cell receptor No attachment = No infection Virus acts as a “key” to the receptor The Lytic Cycle

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2nd Step: Entry Virus enzyme weakens cell membrane Genetic material (DNA or RNA) enters host cell The Lytic Cycle endocytosis

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3rd Step: Replication Virus DNA/RNA uses ribosomes to make virus proteins Proteins created by transcription/translation Virus proteins make new virus parts The Lytic Cycle

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4th Step: Assembly (formation) New virus parts are assembled in the cytoplasm The Lytic Cycle

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5th Step: Lysis & Release Virus enzyme causes cell membrane to “lyse” New viruses are released to find new host Cycle repeats The Lytic Cycle

Viral Transcription & Translation : 

Viral Transcription & Translation If DNA Virus: 1) Viral DNA injected 2) Viral DNA transcribed into viral mRNA 3) Viral mRNA translated into viral proteins If RNA Virus: 1) Viral RNA injected 2) Viral mRNA translated into viral proteins

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1st step: Attachment = Same The Lysogenic Cycle 2nd Step: Entry = Same

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3rd step: Replication Virus DNA combines with cell DNA, and waits… Cell divides as usual Each new cell will have virus DNA inside Lysogenic Cycle

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4th Step: Assembly Same, except many new viruses are being assembled in many cells The Lysogenic Cycle 5th Step: Release Same, except many cells “lyse” releasing many more viruses

Retroviruses : 

Retroviruses Type of RNA virus that contains the enzyme Reverse Transcriptase 1) Virus RNA is injected into cell 2) Ribosome uses virus RNA to create virus DNA 3) Virus DNA combines with cell DNA (becomes latent) 4) Once active, normal steps of transcription/translation followed

How isHIVContracted? : 

How isHIVContracted? High risk activities: 1) Sex (oral, vaginal, anal) 2) Sharing needles (tattoos, piercings, drugs) Low risk activities: 3) Mother to child in womb 4) Breast milk 5) Blood transfusions

Prevention : 

Prevention 100% Effective: Abstinence (not participating in sexual acts) If sexually active: Latex condoms effective when used properly Fact: Latex condoms are the only forms of birth control that protect against STDs If drug user: Change needles

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