Viruses

Question 1

What is the viral genome nucleic acid enclosed in?

Answer 1

Capsid

Question 2

What are the protein subunits which make up the capsid called?

Answer 2

Capsomers

Question 3

What is a cylinder of hexagonal proteins called?

Answer 3

sheet - helical symmetry

Question 4

What shape of capsid is made up of pentagon capsomers?

Answer 4

Icosahedral symmetry - sphere

Question 5

What shape is made when 5 trimer proteins come together?

Answer 5

Pentamer

Question 6

What is a lipid envelope?

Answer 6

Lipid bilayer derived from budding on all helical viruses and many icosahedral viruses

Question 7

What are peplomers?

Answer 7

Membrane anchored glycoproteins which viruses use to attach to cells

Question 8

How do viruses bind to cells?

Answer 8

Receptor ligand binding

or non specific ligand

Question 9

What is a lytic infection?

Answer 9

Acute viral infection causing cell death
release infects thousands more cells
generalised multisystem disease

Question 10

What is latent infection?

Answer 10

Viral infection persists within a cell and doesnt cause cell death
can go dormant
viruses released without killing the cell

Question 11

What is a persistent infection?

Answer 11

cells produce new virus proteins and continually shed virus

doesnt go dormant

Question 12

What is an example of a latent infection?

Answer 12

Herpes virus

Question 13

What are released in response to a viral infection?

Answer 13

Interferons
pro inflammatory cytokines
chemokines

Question 14

What do interferons do?

Answer 14

Cause cells to heighten antiviral defences:
Blocks protein synthesis
Increases MHC expression
Activates antigen presenting cells
Causes fever

Question 15

What stimulates interferons?

Answer 15

PAMPS

Question 16

How do viruses alter cell function?

Answer 16

They cause shutdown of the host cell protein synthesis

Question 17

What are viruses grown in?

Answer 17

Embryonated eggs
cell culture flask
plaque assay

Question 18

What are the stages of viral infection?

Answer 18

Attachment phase
Eclipse phase
Release
Cell lysis

Question 19

What happens in the attachment phase?

Answer 19

There is no free virus in the liquid, its all attached to the cells

Question 20

What happens in the eclipse phase?

Answer 20

There is no virus detected in the liquid or in the cells

due to uncoating of the virus particle to release the nucleic acid

Question 21

What do you need to do to get a positive sense RNA?

Answer 21

Copy a negative sense DNA

Then cap and tail it

Question 22

How do single stranded DNA make mRNA?

Answer 22

Need to be duplicated with enzymes and then copied

Question 23

What type of RNA is incapable of being translated directly?

Answer 23

negative sense RNA

also double stranded RNA uses the negative sense strand so cant be translated directly

Question 24

How is negative sense RNA copied into positive sense?

Answer 24

Using RNA polymerase

Question 25

How do retrovirus DNA replicate?

Answer 25

Use reverse transcriptase

Question 26

WHat does foot and mouth virus attach to?

Answer 26

Integrins

Question 27

WHat is clathyrin?

Answer 27

Causes cell membranes to fold and produce vesicles

Question 28

How is the viral genome released into the cytoplasm?

Answer 28

Acidification of the vesicle causes change to capsid | This forms pore in endosomal membrane

Question 29

What happens to viral genome after its in cytoplasm?

Answer 29

Cut into smaller pieces

Question 30

What is used as a primer on the viral genome?

Answer 30

VPG

Question 31

How does the viral gene replicate?

Answer 31

RNA polymerase copies it many times

Question 32

What destroys the host cells ability to make proteins?

Answer 32

Over production of viral protease | destroys the host cells capping enzymes so cant make RNA