Effect on Host

Question 1

Types of Infections

Answer 1

• Lytic infection: lytic or virulent viruses
• Lysogenic infection: temperate or lysogenic viruses
• Subviral particles: viroids and prions

Question 2

Lytic Infection

Answer 2

○ Enzymes produced which erode the cell wall (bacteria)/cell membrane and cause the cell to rupture
○ Lytic or virulent viruses

Question 3

Lysogenic Viruses

Answer 3

○ Viral DNA/RNA becomes incorporated into the genome of the cell and coexists with the cell
○ Temperate or lysogenic viruses

Question 4

Viroids

Answer 4

□ Short single strands of RNA 
□ Circular structures of 240-400 nucleotides
□ Don’t code for any proteins 
□ No protective coat (unlike viruses)
□ Copies by the host RNA polymerase 
□ Infects plant cells

Question 5

Prions

Answer 5

□ Means proteinaceous infectious particle
□ Even smaller than a viroid and consisting of just a protein of 208 amino acids
□ Only infectious agent without nucleic acid
□ Induces normal PrP proteins to misfold thus forming another prion
- Prions induce the formation of an amyloid fold
□ Prions are involved in Spongioform Encephalopathies
- Long incubation periods
- Usually fatal outcomes