Lec 3 - Viral genetics

Question 1

What genes must viruses always encode?

Answer 1

1. Replication
2. Assembly and packaging
3. Expression and regulation
4. Modulation of cell defences

Question 2

Baltimore Group 1

Answer 2

dsDNA -> mRNA and dsDNA genome by DdDp eg herpes

Question 3

Baltimore Group 2

Answer 3

(+) ssRNA -> dsDNA by DdDp -> mRNA by DdRp eg parvovirus

Question 4

Baltimore Group 3

Answer 4

dsRNA -> mRNA by RdRp eg rotavirus

Question 5

Balimore Group 4

Answer 5

(+) ssRNA -> (-) ssRNA -> mRNA by RdRp eg SINV, dengue, SARS CoV 2

Question 6

Baltimore Group 5

Answer 6

(-) ssRNA -> mRNA by RdRp eg influenza A

Question 7

Baltimore Group 6

Answer 7

(+) ssRNA -> cDNA by RT -> mRNA by DdRp eg HIV

Question 8

Baltimore Group 7

Answer 8

gapped dsDNA with RNA -> repaired by DdDp = cccDNA -> mRNA by RT
RT also makes sgRNA -> (-) ssDNA -> dsDNA genome

Question 9

How do RdRps contribute to viral diversity?

Answer 9

They lack exonuclease proofreading resulting in a high mutation rate

Question 10

What can result from successful mutations?

Answer 10

1. Immune evasion
2. Make vaccines less effective
3. Drug resistance

Question 11

What is recombination?

Answer 11

2 strains coinfect 1 cell, polymerase switches templates, creating heterozygous/chimeric virions

Question 12

What is reassortment and what virus is an example of it?

Answer 12

2 strains of segmented virus coinfect 1 cell and resulting virions’ genomes are a random selection of the segments of both eg influenza A