Mutation

Question 1

Consequences of mutation

Answer 1

• Opportunity for adaptation
• Risk of losing advantages/properties

Question 2

What are the causes of mutation

Answer 2

Failures in NA replication of:

• Cell
• DNA virus
• RNA virus

Question 3

Give the types of mutation incidence

Answer 3

Spontaneous/Induced

Question 4

Causes of induced mutation

Answer 4

• Irradiation
• Mutagenic drugs - halogenated uridine

Question 5

Give the forms of mutation that can occur in the NA chain

Answer 5

• Point mutation
• Sequence mutations
• Substitution
• Insertion
• Deletion
• Inversion
  
  • Frame shift

Question 6

Give the final types of mutation

Answer 6

• Silent mutation
• Lethal mutation
• Conditionally lethal mutation
• Beneficial mutation

Question 7

Silent mutation

Answer 7

• No phenotypic change
• Untranslated region
• Redundant translation code
• Non-important amino acid produced

Question 8

Lethal mutation

Answer 8

Nonsense (stop)

or

Missense (amino acid change)

Question 9

Conditionally lethal mutation

Answer 9

Changes in the multiplication activity

i.e. Thermo-sensitive mutants

Question 10

Give the history of CPV2

Answer 10

1. 1978: CPV2
2. 1979: CPV2a
3. 1984: CPV2b
4. 2000: CPV2c

Question 11

List the influences of mutations on the viral phenotype

Answer 11

• Antigenic change
• Changes in host species specificity
• Changes in organ specificity
• Different tissue tropism (cell cultures)
• Virulence variants
• Cytopathic effects, plaque formation
• Temperature optimum

Question 12

Antigenic change

Answer 12

• Escape mutants
• Influenza - antigenic drift

Question 13

Changes in host species specificity

Answer 13

• Feline panleukopenia → Canin parvoenteritis
• SIV → HIV

Question 14

Changes in organ specificity

Answer 14

• EHV1: Abortion ⇔ EHV4: rhinopneumonitis
• IBR: Rhinotracheitis ⇔ IPV: vulvo-vaginitis

Question 15

Different tissue tropism (cell cultures)

Answer 15

Bovine adenovirus - Kidney/testicular cells

Question 16

Virulence variants

Answer 16

• Newcastle disease: Lento-, Meso-, velogenic strains
• Avian influenza: Haemagglutinin protease cleavage site

Question 17

Cytopathic effects, plaque formation

Answer 17

Aujeszky’s disease virus, BVDV

Question 18

Temperature optimum

Answer 18

• Rhinoviruses, canine herpesvirus
• Rabies vaccine strains

Question 19

Effect of mutation on evolution

Answer 19

• Selective advantages
• Environmental pressure
  
  • Adaptation, niche
• Virus’ evolution is a million times quicker than the host’s

Question 20

Mutation opportunity for protection

Answer 20

• Avirulent strains with conserved antigenic properties
  
  • Attenuated vaccine strains
• Biotechnology, genetic engineering: Accuracy

Question 21

Mutation effection virus strain stabilisation

Answer 21

• Protection from mutations - low passages
• Seed virus, virus banks
• Freeze drying