Viruses

1
Viruses

• Classified as Non-living, so why do we mention
  them in biology?

2
Viruses

• From Latin for poison
• Segments of nucleic acid (DNA or RNA) contained
  in a protein coat (capsid) some also have an
  envelope
• Variety of shapes
• Very small, about 1/10 size of most bacteria
• NO cell membrane, nucleus, or organelles

3
Influenza Virus
4
Terms

• Pathogen agents that cause disease, could be a
  virus, bacteria, fungus, or protist
• Vaccine helps immune system recognize and
  destroy virus or bacteria
• Phage another word for virus

5
Viral Reproduction

• Lytic Cycle cell is destroyed, ruptures (active
  stage)
• Lysogenic Cycle cell survives viral genes
  integrate into the host genes and divide with the
  host (dormant stage)
• Alone, viruses do not use energy.

6
Viral Reproduction
7
Diseases Caused by Viruses

• Bacteriophage virus that infects bacteria (most
  common is T4) sometimes used to benefit patients
  by delivering missing genes (gene therapy)
• Plant viruses tulip break virus, TMV (tobacco
  mosaic virus)
• Animal viruses HIV, colds, Ebola, Hepatitis A,
  B, C, D, E polio, herpes, influenza, mumps,
  rabies, SARS
• Cancer-causing viruses HepBV HepCV (cause
  liver CA), Epstein-Barr Virus (causes lymphoma)
  HPV (causes cervical CA)

8
DNA vs. RNA Viruses

• DNA Viruses are stable and rarely mutate this is
  why you only need to be vaccinated one time
• Ex. Chickenpox virus
• RNA Viruses are less stable and tend to mutate
  frequently this is why a new flu shot comes out
  every year
• Ex. Influenza virus
• Which type is HIV?