Virus Structure

Question 1

What are many mammalian viruses based on?

Answer 1

Icosahedral symmetry

Question 2

What are the simplest viruses?

Answer 2

T=1, 20 sides each with 3 sub-units (60 components)

Question 3

What is quasi-equivalence?

Answer 3

Subdividing, each side dividing into 9. T=3.

Question 4

What is T?

Answer 4

Triangulation number

Question 5

Which viruses break the rules?

Answer 5

Tailed bacteriophages and herpes, they have portals through which genetic material is passed.

Question 6

How do HIV and papilloma break Casper and Klug’s quasi-equivalence theory?

Answer 6

The core is elongated in HIV and papilloma has no hexamers (completely pentamers)

Question 7

How many pentamers and hexamers must there be?

Answer 7

12 pentamers and any number of hexamers

Question 8

Describe poliovirus capsid assembly

Answer 8

There are 3 proteins, VP1, VP3, and VP0. VP0 is cleaved into VP2 and VP4.
VP1, 2 and 3 form the capsid while VP4 works internally to stabilise it.
In the absense of nucleic acid encapsidation VP0 doesn’t cleave so VP4 cannot stabilise resulting in degredation

Question 9

What is cowpea mosaic virus?

Answer 9

T3, -strand segmented genome. 2 viruses must enter the same cell to set up an infection

Question 10

What is blue tongue virus?

Answer 10

Infection in sheep, multi-layered virus, segmented. VP7 forms a T=13 structure

Question 11

what is paramecium bursaria chollera type 1?

Answer 11

Infects paramecium, T=169, 1 pentamer, everything else is a hexamer.

Question 12

How is the nucleocapsid arranged in rabies?

Answer 12

In a spiral/helix

Question 13

What are parasitic wraps?

Answer 13

Self-assemble inside cells without sequence for capsid proteins

Question 14

What is T=3?

Answer 14

Divide each into 9, 180 components but not all subunits are equivalent

Question 15

What is genetic economy?

Answer 15

Using one protein to build the whole capsid.