lecture 31

Question 1

what are the two main parts of a virus

Answer 1

the genetic material and the capsid

Question 2

what is the sructure of the genetic material in a virus

Answer 2

that entirely depends, can be RNA or DNA. double stranded or single stranded

Question 3

whats the capsid

Answer 3

. This is a protein coat which surrounds and protects the genetic material, this is also the part of the virus that normally interacts with the host cell. This Capsid is made of globular protein building blocks.

Question 4

whats the other part of the viruses that not all virus have

Answer 4

Then there is the envelope. This is made of lipids and it surrounds the Capsid coating proteins. Not all viruses have this, those who do are called envelope viruses, those that don’t are naked viruses.

Question 5

whats a naked virus

Answer 5

a virus without an envelope

Question 6

whats an enveloped virus

Answer 6

a virus with an envelope

Question 7

whats the capsid made of

Answer 7

Made of globular proteins.

Question 8

what do the globular proteins of the capsid come together to form

Answer 8

These globular protein building blocks are put into subunits called capsomeres, or capsomers. Capsomers are arranged in different ways around the genome. There are three types of symetary for the arrangement of capsomers.

Question 9

what are the three arrangements of capsid symmetry

Answer 9

There is helical: a kind of rod shape
Icosahedral: very much common
Complex: tend to be bacteriophage

Question 10

describe the helical structure

Answer 10

Helical structures are lots of capsomers that have a slight rotation about their axis of joining to the overall structure. the slight angle resulting in the helical shape

Question 11

describe the icosahedral capsid symmetry

Answer 11

Icosahedral: 20 faced polyhedron. 20 equatorial triangles attached at many veritcies. Many symetrical axis. This is an efficient way of packing in many globular proteins in the capsid.

Question 12

describe the complex structure

Answer 12

Complex contains both. Maybe a icosahedral head and helical tail. These are the shapes we see commonly in bacteriophage, bacteriophage T4 for example.

Question 13

what three shapes can the viral genome take

Answer 13

linear, circular or segmented

Question 14

how long is the viral genome

Answer 14

They also vary largely in size, between 400-1million bases long, with anywhere between 3 genes to 100- 1000.

Question 15

how do viruses like influenza change each year

Answer 15

How viruses like the influenza virus change every year is that they are segmented genomes, so the strains can share and recombine DNA to make a new strand and new strain.
Infulenza has 8 segements.

Question 16

whats a positive sense RNA virus

Answer 16

positive sense acts like mRNA, so their genome can be directly translated into proteins.

Question 17

whats negative sense RNA virus

Answer 17

Negative sense RNA viruses have to have their genome transcribed to then be translated then make the protein.

Question 18

whats a bacteriophage

Answer 18

a virus that only affects bacterial cells

Question 19

describe step one in Lytic (virulent) cycle of bacteriophage infection

Answer 19

attachment: the T4 phage uses its tail fibres to bind to specific surface proteins on an E coli cell that acts as receptors

Question 20

describe step two in Lytic (virulent) cycle of bacteriophage infection

Answer 20

entry of phage DNA. The sheath of the tail contracts punching hole in cell membrane and, injecting the phage DNA into the cell leaving empty capsid outside.

Question 21

describe step three in Lytic (virulent) cycle of bacteriophage infection

Answer 21

3. degradation of host DNA. The cell’s DNA is then hydrolysed and released into the host cell.

Question 22

describe step four in Lytic (virulent) cycle of bacteriophage infection

Answer 22

4: synthesis of viral genomes and proteins. The phage DNA directs production of phage proteins and copies the phage genome by host and viral enzymes, using components within the cell

Question 23

describe step five in Lytic (virulent) cycle of bacteriophage infection

Answer 23

5. three separate sets of proteins self-assemble to form phage heads, tails, and tail fibres. The phage genome is packed inside the capsid and head forms.

Question 24

describe step six in Lytic (virulent) cycle of bacteriophage infection

Answer 24

6. release. The phage directs the production of an enzyme that damages the bacterial cell wall, allowing fluid to enter. The cell swells and finally bursts releasing 100-200 phage particles which go onto affect cells of their own.

Question 25

virus replication is not always lytic, how does it work then

Answer 25

1-4 are the same but in step 5 when assembled the virus is packed into a vesicle by which it is secreted.

Question 26

what does the spike protein do on the covid-19 virus.

Answer 26

The spike protein, what is used to attach to our cells. They attach to specifically the ACE-2 receptor on the cell. The receptor binding domain attaches to the ACE-2.

Question 27

how do our vaccines stop covid

Answer 27

vaccines stop the virus from being able to bind to these parts of our cells.

Question 28

hwo does an enveloped virus enter the cell

Answer 28

Enveloped virus either fuses with host cell membrane or it will be taken up by endocytosis.

Question 29

steps 1-3 are the same for the HIV virus. whats different about step 4

Answer 29

4: retro virus, as it has a viral RNA genome, the RNA genome is used to make a DNA genome. the DNA enters the nucleus. This was all done by reverse transcriptase

Question 30

steps 1-3 are the same for the HIV virus. whats different about step 5

Answer 30

viral integrase chops our genome and inserts the viral genome so thay when we replicate our DNA we replicate HIV aswell.