05 viruses


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  • Which Human Diseases Are Caused By Viruses? Viruses cause diseases in the many organisms that they infect. This slide lists some of the more well-known infectious diseases of humans caused by DNA and RNA viruses. Viruses also cause significant problems in animals and plants. Some viruses, referred to as “tumor viruses,” also can cause cancer. The cancer-causing abilities of some tumor viruses have been demonstrated only in animals. However, there is growing evidence that certain viruses cause specific types of human cancers. For example, some types of papillomavirus, a DNA virus, have been identified as a cause of cervical cancer. HTLV-1, a retrovirus, causes a type of adult leukemia. References: Campbell, N.E., & Reece, J.B. (2002). Biology (6th ed.). San Francisco: Benjamin Cummings. Flint, S.J., Enquist, L.W., Krug, R.M., Racaniello, V.R., and Skalka, A.M. (2000). Principles of Virology: Molecular Biology, Pathogenesis, and Control . ASM Press.
  • 05 viruses

    1. 1. Virus
    2. 2. Virus Definition & Criteria <ul><li>infectious agent with both living and nonliving characteristics that is totally dependent on a host cell for replication (intracellular parasite) </li></ul><ul><li>contain only either DNA or RNA, but not both </li></ul><ul><li>viral genome directs the synthesis of viral components using host cell machinery </li></ul><ul><li>newly synthesized viral components are assembled into a new complete virus called a virion ( pronounced vye-ree-on ) which can then infect another host cell </li></ul><ul><li>b acteriophage : virus that infects only bacteria </li></ul><ul><li>mycophage: virus that infect s only fungi </li></ul>
    3. 3. Characteristics of Viruses <ul><li>Living characteristics of viruses </li></ul><ul><li>reproduce at a fast rate, but only in living host cells </li></ul><ul><li>can mutate / evolve </li></ul><ul><li>Nonliving characteristics of viruses </li></ul><ul><li>are acellular ( no cytoplasm or organelles ) </li></ul><ul><li>not autonomous: carry out no metabolism on their own (i.e. viruses don't grow and divide ) </li></ul><ul><li>replication is fully dependent on the host cell's metabolic machinery ; viral components are synthesized and assembled within the infected host cell </li></ul>
    4. 4. Viral Size Viruses are usually much smaller than bacteria and are submicroscopic. Most range in size from 5 to 300 nm . Thus viruses can infect even other microorganisms. Animal RNA Virus Animal DNA Virus Bacteriophage
    5. 5. Viral Structure <ul><li>A virus consists of these main parts: </li></ul><ul><li>Genome (DNA/RNA) </li></ul><ul><li>Capsid (protein) </li></ul><ul><li>Envelope (lipid) </li></ul>capsid Genome
    6. 6. Viral Structure <ul><li>G enome </li></ul><ul><li>Genetic material of the virus that codes for the synthesis of viral components and viral enzymes for replication </li></ul><ul><li>Can be DNA or RNA but not both </li></ul><ul><li>Can be single or double stranded </li></ul><ul><li>Can be a circular or linear molecule </li></ul><ul><li>Can be a single unit or segmented into parts </li></ul>
    7. 7. Which Human Diseases Are Caused By Viruses? <ul><li>Infectious diseases </li></ul><ul><ul><li>DNA viruses </li></ul></ul><ul><ul><ul><li>Respiratory disease </li></ul></ul></ul><ul><ul><ul><li>Smallpox </li></ul></ul></ul><ul><ul><ul><li>Chicken pox </li></ul></ul></ul><ul><ul><ul><li>Mononucleosis </li></ul></ul></ul><ul><ul><ul><li>Cold sores </li></ul></ul></ul><ul><li>RNA viruses </li></ul><ul><ul><li>AIDS </li></ul></ul><ul><ul><li>Influenza (flu) </li></ul></ul><ul><ul><li>Common cold </li></ul></ul><ul><ul><li>Polio </li></ul></ul><ul><ul><li>Measles </li></ul></ul><ul><ul><li>Rabies </li></ul></ul>
    8. 8. Viral Structure <ul><li>C apsid (core) </li></ul><ul><li>A protein shell surrounding the genome. </li></ul><ul><li>P rotect s and introduce s the genome into host cells. </li></ul><ul><li>V iruses that consist of only a genome surrounded by a capsid and are called nucleocapsid or naked viruses. </li></ul>
    9. 9. Viral Structure <ul><li>E nvelope </li></ul><ul><li>Most animal viruses have an envelope </li></ul><ul><li>C omposed of phospholipids and glycoprotein </li></ul><ul><li>Usually derived from host cell membranes by a proces s called buddin g. </li></ul>
    10. 10. Electron Micrograph of HIV Budding from a T4-Lymphocyte Virus Obtaining Its Envelope from Host Cell Membrane by Budding
    11. 11. Chicken Pox DNA VIRUS varicella-zoster  virus (VZV)
    12. 12. Polio RNA Virus Nonparalytic polio causes symptoms that mimic the flu. Sore throat, fatigue, nausea, diarrhea, a fever, or vomiting. Most cases of nonparalytic polio clear up in a number of days, but a some people go on to develop meningitis, a condition in which the lining of the brain is infected. When a person develops paralytic polio, destroys nerves that control muscles. The infection may be fatal if the brain and respiratory organs become affected. Polio is a serious condition that causes paralysis in about 1% of those infected (paralytic polio).
    13. 13. Herpes DNA Virus Herpes Simplex 1 and herpes simplex 2. The sores are sometimes accompanied by other symptoms such as: headache, fever, and other flu-like symptoms pain, itching, tingling, or tenderness around the genitals painful urination, swollen tender points in the groin and lower abdomen
    14. 14. Genital Warts HPV – human papillomavirus DNA Virus GARDASIL VACCINE
    15. 15. HIV – Human Immunodeficiency Virus HIV MYTHS <ul><li>http://www.youtube.com/watch?v=LaVm3moZo_g </li></ul>