2.1 microscopic look at Viruses and Prions

What is a virus ?

• a non- cellular particle

• contains strands of DNA or RNA surrounded by a protective protein coat

• able to invade living cells in order to reproduce

• cannot live independently outside of the cell

How are viruses grouped?

• Size

• Shape of the capsid ( outer protein layer that surrounds the genetic information

What are the structures of a virus

• genetic material (RNA and DNA)

• protein covering capsid

How does a virus affect a cell?

• attaches to host cell receptor

• injects DNA into the host cell

• Vira; DNA can become incorporated with the cells DNA

What can a virus infect

• Bacteria ( virus that can infect bacteria are called bacteriophage

• plant

• animals

Reproductive cycle of a virus

• Lytic cycle

• Lysogenic cycle

Lytic cycle is?

• viral DNA destroys cell DNA

• viral DNA takes over the cell function and destroys the host cell

• virus replicates and produces progeny phages

• symptoms of viral infection

• rapid infection takes place

Lysogenic cycle

• Viral DNA merges with cell DNA and does not destroy the cell

• infected cell does not produce new viruses

• there are not symptoms of viral infection

What is a DNA virus ?

• Contains only viral DNA

• incorporates the viral; DNA into the cells DNA

• viral DNA then directs the cell to make RNA which then directs ribosomes to make viral proteins

What is a RNA virus ?

• Contains RNA

• RNA once in the cell directs the manufacturing of viral proteins

• viral RNA does not become parts of the cells DNA

What is a prion

• infectious particle that causes damage to nerve cells in the brain and consist of mainly a single protein

What are the characteristics of prion ?

• Made up of proteins that is normally found in your body

• Does not contain RNA and DNA

• Disease results when a factor causes the protein shape to change.