Viral genetics

Question 1

ssDNA viruses

Answer 1

Often small
Can be +, -, or ambisense

Question 2

dsDNA viruses

Answer 2

Have the largest and most complex genomes
Most stable genome
DNA dependant DNA polymerase have high fidelity

Question 3

+ssRNA viruses

Answer 3

Size limited due to RNA fragility
Higher mutation rate because RNA dependent RNA polymerase are more error prone (except coronaviruses)
Majority of plant viruses

Question 4

The majority of plant viruses are which type?

Answer 4

+ssRNA

Question 5

-ssRNA viruses

Answer 5

More genome diversity than +ssRNA
Gene expression and genome replication is harder
Often segmented to increase stability
Must bring its own RNA polymerase

Question 6

Which virus is segmented?

Answer 6

-ssRNA

Question 7

Which viruses must bring its own polymerase?

Answer 7

-ssRNA

Question 8

Reverse transcription

Answer 8

2 +ssRNA to 1 dsDNA
Very error prone = rapid genetic variation
2 +ssRNA copies promotes recombination
dsDNA integrates into host genome for lifelong infection

Question 9

Why don’t we need to worry about bacteriophages?

Answer 9

Genome not recognizable and decidable by our cells

Question 10

Viral genome compression

Answer 10

Selective pressure to maximize genetic capacity and minimize genome size

Dense genome increases replication rate compared to host

Question 11

Gel electrophoresis

Answer 11

Nucleic acids are negative

Useful for analyzing intact genomes, segmented genomes, and sequencing

Question 12

PCR

Answer 12

Allows detection of minuscule amounts of viral nucleic acids

Use RT-PCR for RNA viruses

Question 13

Transfection

Answer 13

Infection of cells by nucleic acids alone (use plasmids of each gene)

Question 14

Transduction

Answer 14

Transfer of genome from packaging cell to the target cell

Question 15

Strain

Answer 15

Same viruses but different isolates (flu from two countries)

Question 16

Type

Answer 16

Serotype of the same viruses (Dengue 1-4 produce different antibody responses)

Question 17

Variant

Answer 17

Mutant with different phenotype from WT (Covid variants)

Question 18

Which viruses have a higher rate of mutation?

Answer 18

RNA because their polymerase can’t proofread (except coronaviruses)

Question 19

Quasi species

Answer 19

Mixture of viral genomes in a population

Question 20

Defective Interfering (DI) particles

Answer 20

Non infectious
Takes up machinery
Can trigger immune response

Question 21

Consequences of superinfection

Answer 21

Complementation - increase fitness of one or both parents

Recombination - occurs in all DNA viruses and only RNA viruses with a DNA intermediate

Reassortment - segmented genomes get mixed

Question 22

Virome

Answer 22

All viruses in a given environment