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The Virus

The Virus. What they are and how they work. What is a virus. Viruses are non-living particles of DNA, RNA, proteins , and in some cases, lipids. *Virus is the Latin word for poison. Characteristics…. Must invade a living host cell to reproduce. Viruses are parasitic.

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The Virus

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  1. The Virus What they are and how they work

  2. What is a virus Viruses are non-living particles of DNA, RNA, proteins, and in some cases, lipids. *Virus is the Latin word for poison

  3. Characteristics…. • Must invade a living host cell to • reproduce. • Viruses are parasitic. • Viruses are smaller than bacteria. • Viruses cannot move, grow or • use energy.

  4. I am sick with a virus can I have some antibiotics?

  5. *NO!!!! Antibiotic means against life . . . Viruses aren’t living!!!! We can vaccinate beforehand, but once you are sick with a virus, Dr.’s can only give you stuff for symptoms.

  6. Viral Structure Basic Structure: DNA or RNAcore Protein coat =capsid – This determines the shape of the virus

  7. Other structures Tobacco Mosaic Virus

  8. Polyhedral Virus (Many sides) Causes foot-and-mouth disease

  9. Retroviruses • “retro-” means backwards – these viruses workbackwards. Instead of copying RNA from the DNA, they copy DNA from their RNA. • Retroviruses use RNA • Make a copy of DNA from their RNAusingenzyme reverse transcriptase. • DNA is inserted into host DNA • Can remain dormant for a long • time • Ex: HIV causing AIDS

  10. Retrovirus = Hard to fight

  11. Bacteriophage Bacteriophage is a virus which attacksbacteria! * “phage” = Greek = eating

  12. Lytic Cycle Lytic Infection: Virus insert its DNA or RNA, Our cells replicate the viral DNA, makes copies of the virus, and the virus causes the cell to burst *Lysis = burst • Think – high jacking the cell!!

  13. Lysogenic Cycle Lysogenic Infection: A virus integrates its own DNA into the DNA of the host cell, and the viral genetic information replicates along with the cell’s DNA It lies dormant in your body and can be undetected for several years. (You may be infected by a virus and not even know it!) The virus can become harmful and lyse at anytime. Ex: Herpes simplex, HIV, chickenpox virus causing shingles

  14. The prophage may leave the host’s DNA and enter the lytic cycle. The viral DNA is called a prophage when it combines with the host cell’s DNA. Although the prophage is not active, it replicates along with the host cell’s DNA. Many cell divisions produce a colony of bacteria infected with prophage. A Lysogenic Infection

  15. Lytic vs. Lysogenic

  16. Lytic cycle Lysogenic cycle • Viral DNA becomes • part of the host cell’s DNA • Host cell is not destroyed – • virus replicates with host cell. • Viral DNA takes over host cell’s DNA. • Host cell is • destroyed • (Lysis = to burst) Both are viral replication cycles

  17. *Are they alive? Living things: Are made up of cells Reproduce Based on a universal genetic code Grow and develop Obtain and use materials and energy Respond to their environment Maintain stable internal environment Change over time Show organization NO NO/YES YES NO NO NO NO YES - MUTATE NO

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