Transcript VIRUSES
http://pandemic2.org/ The girl who survived Rabies Viruses! EBOLA Ebola Virus Relative Size Do NOW How Viruses Attack • http://www.youtube.com/watch?v=Rpj0em EGShQ • http://video.pbs.org/video/1240086878/ • 3:17 1918, Spanish Flu, • Swine Flu, New Report Swine Flu Flu VIRUSES Viruses are particles containing: 1. Nucleic acid 2. Protein coat (capsid) They can reproduce only by infecting living cells. All viruses enter living cells and use the infected cell( host) to produce more viruses. • Special proteins on the capsid “trick” the host cell to let the virus in. The host cell then bursts and is destroyed Types of Viruses • DNA viruses • More Stable less prone to mutation • Respond well to vaccination • Ex: smallpox, chicken pox, herpes, HPV, Hepatitis B • RNA viruses • Mutate quickly • Require frequent vaccinations • Ex: Influenza (flu), HIV, Rabies Different Hosts Host cell is very specific • Animal hosts: rabies, HIV, chicken pox • Plant hosts: tobacco mosaic virus, • Bacteria: Bacteriophage Ex. Rabies Virus can only exist in an animal Examples of Viral Disease • Smallpox, the common cold, chickenpox, influenza, shingles, herpes, polio, rabies, ebola, and HIV Small Pox Smallpox killed over 500 million people in the 20th century! Compared to: 320 million deaths caused by wars, the Spanish flu, and AIDS combined Amherst bring Smallpox blanket to native Americas POLIO Figure 1.15B: The press portrayed Roosevelt as a robust, physically strong leader. Lytic vs. Lysogenic Lytic Infection - Viruses inject their DNA or RNA and take over the host to make new viruses - The viruses “pop” the cell to spread A spacecraft injecting genetic material into a host cell. The Lysogenic Cycle (Sneaky!) Lysogenic Cycle 1. Virus injects its DNA into host cell 2. Viral DNA integrates into the host DNA 3. A host cell makes copies of the virus every time it divides. The viral DNA embedded in the host’s DNA is called a prophage. Replicates in the host cell Viral DNA can leave the host DNA and enter the lytic Cycle Retroviruses • Retroviruses contain RNA. • Make a DNA copy FROM their RNA. • Then this DNA is inserted into the DNA of the host cell. HIV (humanimmunodeficiency virus) can lead to AIDS (acquired immunodeficiency syndrome) http://www.livescience.com/16909-magic-johnson-hiv-aids-anniversary.html Defense • Vaccination offers protection for uninfected individuals (weakened version or partial version of virus) • Works by stimulating immune system so that the virus will be recognized if infected Are Viruses Living or Non-living?? Ecuador/Galapagos