Viruses

1
Viruses

• Virus A noncellular particle composed of genetic
  material that can invade living cells.
• Viruses are considered by most to be non-living
  since they lack metabolism and are not made of
  cells.
• Are extremely small
• Are usually very specific as to what cells they
  can invade

2
Structure of a Virus

• Contain core of genetic information (either DNA
  or RNA).
• Genetic material surrounded by a protein coat
  called a capsid.

3
Life Cycles of viruses Lytic infection

• Infection Virus identifies an attaches itself to
  a host cell. The genetic material is then
  injected into the host cell.
• Growth Genetic material of virus overrides host
  cell's activities. Cell is now instructed to
  replicate viral genetic material and protein
  coats.
• Lysis Cell is lysed "broken open" and new
  viruses are released to infect other cells. This
  kills the host cell

4
Life Cycles of viruses Lysogenic infection

• Similar to lytic infection however important
  differences exist
• Instead of immediately replicating, viral DNA
  incorporates itself into the host cell's DNA.
• Will remain dormant for significant amounts of
  time.
• Give certain conditions, the virus will enter
  it's lytic phase similar to a normal lytic
  infection

5
Retroviruses

• A new form of virus has been identified known as
  a retrovirus.
• Retroviruses are RNA viruses which can conduct a
  process known as Reverse Transcription
• In reverse transcription RNA is used to make DNA
  (the reverse of the normal RNA transcription
  process).
• HIV is a retrovirus.

6
Virus Shapes