Topics

Question 1

Topic 1: Place and significance of viruses in the biosphere, evolution of viruses

Answer 1

Morphology:

• Two types of forms:
• Virions:
  1. A particle that transfferes genetinc info.
  2. Shape varies.
  3. Content: DNA, RNA, Proteins and lipids
• Vegetative virus: The infected cell (active)

Reproduction:

• One replication cycle + millions of viruses.
• Lacks all cell organelles and enzymes  no energy production.

Occurrence:

• Widespread. Effects bacteria (phages), fungi, plants, animals and humen.
• Most viruses are not pathogenic (orphan viruses).

Origin of viruses:

• Simplest DOES NOT necessarily mean the oldest!
• Theories:

Cell degeneration – A cell that lost its independence.
Runaway cell:
1. mRNA  +ssRNA
2. Chromosome-fragmentdsDNA virus.

Question 2

Topic 1: Place and significance of viruses in the biosphere, evolution of viruses
SIMPLE

Answer 2

Morphology:
* Two types of forms:
- Virions:
- Vegetative virus: The infected cell (active)
Reproduction:
Occurrence:
Origin of viruses:

Question 3

Topic 2: Propagation of viruses -

SIMPLE

Answer 3

Aims:
* Inoculation of embryonated eggs:

Requirements:

1. Embryonated.
2. SPF.
3. White shelled.

Preparartion:
Inoculation:
After Inoculation:

Question 4

Topic 2: Propagation of viruses -

Answer 4

Aims:

• Detection of viruses (diagnosis).
• Large-scale production of viruses (analytic study, vaccine production).

Methods:
* Experimental infection of animals:
Not common.
Rabies, African horse fever, Arbovirus.
Vaccine production (rare).

* Inoculation of embryonated eggs:
Requirements:
1. Embryonated.
2. SPF.
3. White shelled.

• Preparartion:
  1. Translumination.
  2. Disinfection.
  3. Drilling through shell.
• Inoculation:
  1. Yolk sac – picorna virus.
  2. Allantoic cavity and amniotic cavity – Para-, Ortho- and Coronaviridae viruses.
• After Inoculation:
  1. Sealing shell.
  2. Incubation.
  3. Control.