8: Mutations

Question 1

What is mutation?

Answer 1

• independent changes in the genetic material

- the source of evolution

Question 2

What causes mutation?

Answer 2

failures in the NA replication

• Cell: 10^9
• DNA virus: 10^5
• RNa virus: 10^3

Question 3

What are the type of mutations?

Answer 3

• spontaneous

- induced

Question 4

What are the types of induced mutation?

Answer 4

• irradiation: UV, X-ray, atomic radiation

- mutagenic drugs: halogenated uridine

Question 5

What are the different forms of mutation?

Answer 5

• point mutation
• sequence mutations
• substitution
• insertion
• deletion
• inversion (frame shift)

Question 6

What are the results of mutation?

Answer 6

• silent mutation
• lethal mutation
• conditionally lethal mutation
• beneficial mutation

Question 7

What is Silent mutation?

Answer 7

no phenotypic change

• untranslated region
• redundant translation code
• not important amino acid

Question 8

What is Lethal mutation?

Answer 8

nonsense (stop) or missense (aa. change)

Question 9

What is Conditionally lethal mutation?

Answer 9

• changes in the multiplication activity

- i.e: thermo-sensitive mutants

Question 10

What is Beneficial mutation?

Answer 10

• rare

- accidental

Question 11

What are the influences 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 effect, plaque formation
• temperature optimum

Question 12

Antigenic change on the viral phenotype:

Answer 12

• escape mutants

- influenza - antigenic drift

Question 13

Changes in host species specificity on the viral phenotype:

Answer 13

• feline panleucopena –> canine parvoenteritis

- SIV –> HIV

Question 14

Changes in organ specificity on the viral phenotype:

Answer 14

• EHV1: abortion EHV4: rhinopneumonitis

- IBR: rhinotracheitis IPV. vulvo-vaginitis

Question 15

Different tissue tropism (cell culture) on the viral phenotype:

Answer 15

Bovine Adenovirus - kidney/testicular cells

Question 16

Virulence variants on the viral phenotype:

Answer 16

• newcaste disease: lento-, meso-, velogen strains

- Avian influenza: haemagglutinin protease cleavage site

Question 17

Cytopathic effect, plaque formation on the viral phenotype:

Answer 17

• Aujeszky´s diease virus, BVDV

Question 18

Temperature optimumon the viral phenotype:

Answer 18

• rhinoviruses, canine herpesvirus

- rabies vaccine strains

Question 19

Opportunity for protection:

Answer 19

• avirulent strains with conserved antigenic properties –> attenuated vaccine strains
• biotechnology, genetic engineering: accuracy

Question 20

What is the temp. in freeze drying in the Stabilization of virus strains?

Answer 20

• 80C, -196C