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Viruses

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The CCHS's Biology Department's lecture on viruses.

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Viruses

  1. 1. Viruses
  2. 2. Discovery of Viruses <ul><li>1800’s- Became aware of an infectious particle smaller then bacteria </li></ul><ul><li>1935- Wendel Stanley isolates and crystalize the tobacco mosaic virus </li></ul>
  3. 3. Characteristics of Viruses <ul><li>Not considered to be alive </li></ul><ul><ul><li>Require a host cell to reproduce </li></ul></ul><ul><ul><li>Do not carry out all of the process of life </li></ul></ul><ul><li>Made only of protein, nucleic acids, and sometimes carbohydrates </li></ul>
  4. 4. Viral Categories <ul><li>Shape </li></ul><ul><ul><li>Enveloped </li></ul></ul><ul><ul><li>Helix </li></ul></ul><ul><ul><li>Isohedron (Polyhedron) </li></ul></ul><ul><li>Type of Nucleic Acid </li></ul><ul><ul><li>DNA-1x and 2x </li></ul></ul><ul><ul><li>RNA-1x and 2x </li></ul></ul>
  5. 5. Retroviruses <ul><li>Have RNA Genomes </li></ul><ul><li>Contain special enzymes that can transcribe RNA to DNA </li></ul><ul><li>Reverse Transcriptase </li></ul><ul><li>HIV </li></ul>
  6. 6. Viroids and Prions <ul><li>Viroids are short RNA segments capable of self replication inside a host. </li></ul><ul><li>Cause many plant diseases </li></ul><ul><li>Prions are small protein only particles that cause disease in a host. </li></ul><ul><li>Mad Cow Disease, Chronic Wasting Disease, Creutzfeldt-Jakob Disease </li></ul>
  7. 7. Viral Replication <ul><li>Defined as Obligate Intracellular Parasites </li></ul><ul><li>Two types of replication </li></ul><ul><ul><li>Lysogenic </li></ul></ul><ul><ul><li>Lytic </li></ul></ul>
  8. 8. Lytic Cycle <ul><li>Virus is considered Virulent </li></ul><ul><li>Immediately begins replication after infection </li></ul><ul><li>Quickly kills the cell </li></ul>
  9. 9. Lytic cycle Steps <ul><li>Attachment- the virus must connect with the right type of host cell. </li></ul><ul><li>Insertion- the virus’s genome (either DNA or RNA) is inserted into the host cell </li></ul><ul><li>Replication- the viral genome is replicated </li></ul><ul><li>Burst- the cell gets so full of viruses that it bursts open </li></ul>
  10. 10. Lysogenic Cycle <ul><li>After the viral genome enters the cell the nucleic acid enters the cells genome </li></ul><ul><li>Can remain dormant for a potentially long time </li></ul><ul><li>Enters the lytic cycle to complete its cycle </li></ul>
  11. 11. Lysogenic cycle steps <ul><li>Attachment- the virus must connect with the right type of host cell. </li></ul><ul><li>Insertion- the viral genome (either DNA or RNA) is inserted into the host cell </li></ul><ul><li>Integration- the viral DNA inserts itself into the host cell’s DNA </li></ul><ul><li>Replication- the viral genome is replicated </li></ul><ul><li>Burst- the cell gets so full of viruses that it bursts open </li></ul>
  12. 12. Evolution <ul><li>Viruses evolve very quickly due to faulty genome reproduction enzymes </li></ul><ul><li>Causes multiple strains to come about very quickly </li></ul>
  13. 13. Viral Diseases <ul><li>Many different diseases are caused by viruses </li></ul><ul><li>Difficult to treat </li></ul><ul><ul><li>Vaccines - use live, attenuated, or dead viral particles (2) </li></ul></ul><ul><ul><li>Anti-viral drugs- interferes with viral protein production and/or specificity proteins </li></ul></ul>

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