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Viruses

Viruses. Non-Living Infectious Agents. What are they? How do they work? Where do they come from? And… What good are they?. Non-viral Infectious Agents. Viroids- The smallest known particle that can replicate. Single Strand of RNA Disrupt plant cell metabolism Can destroy entire crops

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Viruses

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  1. Viruses Non-Living Infectious Agents What are they? How do they work? Where do they come from? And… What good are they?

  2. Non-viral Infectious Agents • Viroids- The smallest known particle that can replicate. • Single Strand of RNA • Disrupt plant cell metabolism • Can destroy entire crops • Prions – Abnormal forms of proteins that clump together inside cells. • Clumping eventually kills the cell • Example • Mad Cow Disease

  3. Overview of Viruses • Nonliving • Composed of Nucleic acid and protein • Cause many diseases • Virology – Study of Viruses • Comparison of Viruses and Cells below

  4. Characteristics of Viruses • 2 essential features • 1. Nucleic Acid • May be DNA or RNA • Helical, closed loop, or long strand • 2. Protein Coat – called CAPSID • Some have ENVELOPE • Ex. Influenza, chickepox, herpes simplex, HIV • VIRAL SHAPE • Icosahedron – 20 triangular faces • Ex.) herpes, chickenpox, polio • Helix – Coiled spring • EX.) Rabies, measles, tobacco mosaic

  5. Bacteriophages: like tiny little syringes that inject DNA from the virus into the cell

  6. 1. Attachment- Virus finds host cell Bacteriophage Host cell DNA 2. Entry- Viral DNA injected into host 5. Lysis & Release- viruses burst out of host (dies); Find new host 3. Replication- Host makes viral DNA & parts 4. Assembly- New viruses made Lytic Cycle

  7. Here is a non-enveloped bacteria virus inserting it’s DNA into a bacterial cell.

  8. Some virus are pushed out by the cell, taking some of the cell membrane with them.

  9. Lysogenic Cycle • After Step #2 of the Lytic Cycle, the Virus may become Dormant and enter into the Lysogenic cycle • Dormant- non-active time of virus • Host is infected, but doesn’t know it • Ex: Herpes (cold sores) Person doesn’t have them all the time, but has “outbreaks” throughout year • Ex: HIV Mono

  10. 5. Cell enters back into Lytic Cycle- Assemble, Lysis & Release From Step #2 Lytic cycle, enters Lysogenic cycle here Many cell divisions 4. Cell Multiplication – Host replicates with viral DNA 2. Entry- Viral DNA injected into host 3. Integration -Viral DNA becomes part of host DNA Lysogenic Cycle Provirus

  11. Classification of Viruses 1. By Shape 2. Host type3. function Retroviruses attack a certain way. DNA viruses attack another way. Animal viruses Plant viruses Bacteria viruses

  12. Viruses and Human Disease • Control and Prevention of spread. • Vaccination & Antiviral drugs • Ex.) chickenpox vaccine, AZT, Acyclovir, protease inhibitors. • Emerging Viruses – exist in isolated habitats • Do not usually infect humans unless environmental conditions favor contact. • Several viruses are now linked to cancers such as leukemia, liver cancer, Burkitt’s lymphoma, cervical cancer.

  13. English physician and scientist from Berkeley, Gloucestershire, who was the pioneer of smallpox vaccine

  14. Cowpox and smallpox are closely related, but cowpox is a much less serious disease than smallpox. • Jenner noticed milkmaids were immune to smallpox. • He used puss from a cowpox blister to inocculate an 8 year old boy • He called his method “vaccination,” from the Latin word vacca, or cow, and today we use vaccination to refer to immunization against any disease.

  15. A vaccine contains a killed/weakened part of a germ. • When a person receives a vaccine, the body reacts by making protective antibodies.

  16. Wendell M. Stanley • Wendell M. Stanley crystallized and described the molecular structure of the tobacco mosaic virus.

  17. PAPOVAVIRUSES: Tumor causing virusesMost common: Human papillomavirus (HPV) (warts)

  18. ADENOVIRUSES: causes respiratory issues and pink eye

  19. HERPESVIRUSES: easily transmitted by direct contact with a lesion or the body fluid of an infected individual

  20. POXVIRUSES

  21. PICORNAVIRUSESThe name is derived from pico, meaning small, and RNA, referring to the ribonucleic acid genome, so "pico-rna-virus" literally means small RNA virus.Ranges from the common cold to polio!

  22. MYXOVIRUSES

  23. RHABDOVIRUSES

  24. RETROVIRUSES: genes are encoded in RNA instead of DNA

  25. Here is a classic picture of HIV viral progeny being released from the surface of a T- cell. Notice the membrane coating they receive.

  26. Ebola Virus • Some therapies that have worked have been when patients receive blood from convalescent patients 26

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