Replicative cycles

Question 1

What are the two key variables used to classify viruses that infect animals

Answer 1

• an RNA or DNA genome, either single stranded or double stranded
• the presence or absence of a membranous envelope

(whereas few bacteriophages have an envelope OR an RNA genome, many animal viruses have both

Question 2

Viral envelopes

Answer 2

• many viruses that infect animals have a membranous envelope
  -viral glycoproteins on the envelope bind to specific receptor molecules on the surface of a host cell
  -the viral envelope is usually derived from the host cell’s plasma membrane as the viral capsids exit
• other viral membranes form from the host’s nuclear envelope and are then replaced by an envelope made from golgi apparatus membrane (i.e herpesvirus)

Question 3

Retrovirus

Answer 3

use reverse transcriptase to copy their RNA

Question 4

provirus

Answer 4

viral DNA that is integrated into the host genome is called a provirus

Question 5

vaccine

Answer 5

harmless derivative of a pathogen that stimulates the immune system to mount defenses against the harmful pathogen

Question 6

3 causes of rapidly emerging viral diseases in humans is mutation

Answer 6

mutation of existing viruses into new ones that can spread more easily

spread of a viral disease from a small isolated human population

spread of existing viruses from other animals

Question 7

prions

Answer 7

infectious proteins that appear to cause degenerative brain diseases in animals