RNA viruses

Question 1

Are ribosomes a feature of viruses?

Answer 1

no

Question 2

Describe positive-strand RNA virus genomes

Answer 2

• simple open reading frame
• cassette their proteins into structural and non-structural
• 5’UTR and 3’UR
• sometimes Cap
• sometimes Poly(A)
• 1 start
• 1 stop

Question 3

Which direction do negative strand RNA viruses get read?

Answer 3

right to left

Question 4

What do negative strand RNA proteins do first when they invade a cell?

Answer 4

begin by replicating (must contain a polyerase in its capsid)

Question 5

What are the four types of negative-strand RNA genomes?

Answer 5

• simple
• multiparte, simple
• multiparte, simple, ambisense
• multiparte, complex, ambisense

Question 6

What does ambisense mean?

Answer 6

some bits of RNA translate n both directions

Question 7

What is a mononegavirale?

Answer 7

single-stranded, single pieces of anti-sense viral RNA (must have a RNA polymerase as cells don’t have one)

Question 8

Can viruses make a two codon translation?

Answer 8

yes

Question 9

What does para mean?

Answer 9

correct/normal

Question 10

What does ortho mean?

Answer 10

similar

Question 11

Name the segmented viruses (BOARing)

Answer 11

bunyavirus, orthomyxovirus, arenavirus and reovirus

Question 12

What makes it possible for reassortment of genetic information?

Answer 12

segmented genomes

Question 13

What does reassortment achieve?

Answer 13

rapid generation of genetic diversity

Question 14

What must all viruses contain at some point in their life cycle?

Answer 14

double stranded RNA as they have to replicate

Question 15

What triggers an innate response?

Answer 15

the replication intermediate double stranded rNA which is normally never seen

Question 16

In retroviruses where is the nucleocapsid protein found?

Answer 16

on the left, near 5’ end

Question 17

Where is the polymerase in retroviruses?

Answer 17

middle

Question 18

How do retroviruses replicate?

Answer 18

make DNA from RNA and then RNA from the DNA that has been made

Question 19

Are retroviruses nuclear?

Answer 19

yes always because they are DNA viruses half of the time

Question 20

Why do viruses spread so quickly?

Answer 20

once a cell is infected it defends the virus inside it to avoid superinfection. It pushes the other virus away causing other cells to become infected (this occurs via A33 and A36 proteins)

Question 21

What does VEHCS stand for?

Answer 21

Virally Encoded Host Cell Shutoff

Question 22

How does polio produce viral proteins?

Answer 22

1. Removes the cap binding complex on mRNA so that translation can’t occur
2. Polio can bind directly to the ribosome using the internal ribosome entry site so it can produce proteins

Question 23

How does HSV work?

Answer 23

to remain hidden it stays silent
-turns off everything other than a series of micro RNAs that control the host cell (not antigens) (immosilent and invisible)

Question 24

What makes a virus more likely to spread?

Answer 24

by keeping host cells alive (more chance for transmission than if host cells are dying) (need to be less virulent)

Question 25

What is the role of the HERV-W virus?

Answer 25

mediates the cell-cell fusion which forms the synciotrophoblast forming the fetal-parent barrier

Question 26

Do all viruses contain RdR polymerases?

Answer 26

no HIV has a RdD polymerase (RNA dependent DNA polymerase)