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Question 1

How many types of simetry does RNA have?

Answer 1

Regarding RNA viruses, there are two types of symmetry: icosahedral and helical

Question 2

How many types of simetry does DNA have?

Answer 2

Regarding DNA viruses, there are three types of symmetry: icosahedral, helical and complex.

Question 3

Does animal virus have round-shaped?

Answer 3

Yes, independently of the symmetry.

Question 4

Does the helical geommetry have naked virus

Answer 4

No, they don’t have naked viruses

Question 5

Are plant viruses all naked?

Answer 5

Yes, they are all naked

Question 6

Plant virus have their genome split?

Answer 6

Yes, they can have different viral particles

Question 7

Which are the difference between split genome and segmented genome?

Answer 7

• Split genome: The genome is split in segments and each segment is inside a different viral particle.
• Segmented genome: The genome is cut in segments and each segment is inside a single viral particle.

Question 8

Why does plant viruses have its genome split?

Answer 8

Because this allows them to have very small viral particles. They need to have small viral particles because when the virus needs to go from one cell to another, it needs to go through a small and narrow pores (plasmodesma) that communicates each cell.

Question 9

Which is the disadvantage of having the genome split?

Answer 9

There’s a disadvantage: in order to form new viral particles, all the viral particles need to be infecting the same host cell at the same time

Question 10

Which are the two main types of symmetry?

Answer 10

Icosahedral and helical

Question 11

Can viruses have a fourth type of symmetry?

Answer 11

Yes, and it’s called complex symmetry, they are enveloped viruses and that they have like a hairy structure surrounding the envelope

Question 12

Does all bacteriophages have the retractil tail and the mixed symmetry?

Answer 12

Not all of them have neither retractile tail nor mixed symmetry

Question 13

What is a baculovirus?

Answer 13

This virus infects insect cells. They have two conformations:
- Conformation 1: When it goes from one insect cell to another. It has a peculiar shape.
- Conformation 2: When the insect dies and is kept in the environment, this virus changes its conformation. In this conformation, the virions are surrounded by matrix of proteins (polihedrin).

Question 14

What can happen when we try to see viruses throgh EM?

Answer 14

For the treatment that viruses need to go through to be observed, some of them collapse because they gey dried.

Question 15

How can we see a virus in a negative staining?

Answer 15

The virus is seen in white and the heavy metals are seen in black (they surround the virus)

Question 16

How can we see a virus in a positive staining?

Answer 16

the virus is seen in black and the heavy metals are seen in white

Question 17

Which is the resolution of a EM?

Answer 17

The resolution of the electron microscope is between 5-7 Å.

Question 18

What is acapsomere?

Answer 18

It’s a morphological unit that forms the capsid of an icosahedral and helical virus and that is formed by several proteins

Question 19

Is a capsomere a protein?

Answer 19

a capsomere is not a protein, a capsomere is formed by proteins. There are two types of capsomers: pentamers (formed by five proteins) and hexamers (formed by six proteins).

Question 20

How are isometric viruses formed?

Answer 20

They are formed by assembling similar pieces in a very similar way, in a symmetric way, forming this round-shape structure.

Question 21

Which are the two rules for the success of the capsid formation?

Answer 21

• Rule 1: They are identical bond contacts with its neighbours. This leads to a symmetrical arrangement.
• Rule 2: They are usually non-covalent bonds. This means they are reversible, error-free. They tend to assemble in a way that is thermodynamically favourable

Question 22

Can the genome help in the process of assembling?

Answer 22

Sometimes the genome can help in the process of assembling because there are some sequences that attract proteins of the capsid. It’s like these proteins tend to bind to some parts of the genome.

Question 23

What happens if one of the sides of the icosahedral structure is divided into smaller sides?

Answer 23

Then, we will no longer be talking about icosahedra but icosadeltahedra.

Question 24

What is the triangulation number (T)?

Answer 24

It’s the number of small sides in which the original side is divided. The higher the triangulation number is, the more the icosahedral virus tends to be round- shaped.

Question 25

Where we can find hexamers?

Answer 25

These proteins can be found in the sides, not on the vertexes.

Question 26

Does the number of vertexes depends on the triangulation number?

Answer 26

The number of vertexes, independently from the triangulation number, will remain the same always.

Question 27

What can we deduce just by knowing the triangulation number?

Answer 27

Just by knowing the triangulation number, we can deduce the number of proteins, number of sides, number of pentamers and hexamers (number of capsomeres).

Question 28

Which is the equation that describes the structure of the helix (this formula would be different for each helical virus)?

Answer 28

P=p*μ. P corresponds to the height of a whole turn, p corresponds to the height of one protein respecting the previous one and μ corresponds to
the number of proteins that are in a whole turn.

Question 29

Is the vrial genome inside the helix on helical viruses ?

Answer 29

the viral genome is inside the helix making a spiral. This happens because the genome accompanies the proteins of the capsid. These proteins are formed by cationic amino acids and they tend to bind to the viral genome as this is anionic

Question 30

How is this helical structure formed?

Answer 30

Usually, it’s not formed just by adding one protein after another in a spiral way. What happens is that there are interactions between specific amino acids of the proteins.

Question 31

From where is taken the envelope of the enveloped viruses?

Answer 31

The envelope is taken mainly from the membrane of the host cell, but sometimes it can be taken from the nuclear membrane of the Golgi membrane.

Question 32

How is it formed the enveloped virus?

Answer 32

the machinery of the host cell produces the glycoproteins that will be attached to the envelope of the virus . When these glycoproteins are formed, they have a signal sequence that tells them to go to the membrane that is going to form the envelope of the viral particles. Later on, when the virus is going to exit the host cell, it takes the cell’s membrane with those glycoproteins inserted.

Question 33

What are the matrix proteins?

Answer 33

It’s proteins that anchored in one side of the capsid of the viral particle and in the opposite side of it. This structure is quite compact. It’s synthesised by the host cell’s
machinery, they have a signal sequence that tells them they need to be close to the inner side of the host cell’s membrane.

Question 34

Which are the viral envelope glycoptroteins

Answer 34

• Integral membrane glycoproteins
• Ectodomain (external domain): attachment, antigenic sites and fusion
• Internal domain: assembly
• They tend to oligomerise and form spikes

Question 35

Why are the glycoproteins important for the virus and for us?

Answer 35

Because for the virus, these glycoproteins allow the attachment of the virus to the receptor of the host cell and meditate the fusion of the membrane. for ourselves, these glycoproteins are antigenic sites. That means that we can recognise them and generate antibodies against them.

Question 36

What is a Sindbis virus?

Answer 36

Sindbis virus is an enveloped virus. When it was analysed its structure, it was seen that the glycoproteins of the membrane had symmetry. They observed that the glycoproteins were attached to certain domains of the capsid. This way, the symmetry of the capsid is transmitted to the glycoproteins attached to it.

Question 37

Which are the features about Adenovirus?

Answer 37

It has a special shape: it looks like a satellite. It has fibbers that come from each vertex (it has twelve fibbers total). These fibbers allow the virus to recognise the host cell’s receptors.

Question 38

Which are the features about Herpes?

Answer 38

It has an isometric symmetry with twelve pentamers (meaning, twelve vertexes). One important thing is that only one of the twelve vertexes has a porus. When the virus enters the host cell, this porus gets attached to the nucleoporus, allowing the viral genome to be transferred from the virus to the nucleus of the host cell.

Question 39

Which are the features about Reovirus?

Answer 39

It’s a family of virus that causes intestinal diarrhoea (it’s a digestive virus). I its transmission type is called faecal/oral transmission. This type of virus has to remain in the environment and still be able to infect. They have to be resistant. This resistance is given by a doble capsid. Both capsids don’t have the same triangulation number. They are naked viruses (they can resist better the environmental distress).

Question 40

Which are the features about Mimivirus?

Answer 40

It infects amoebas. It has an icosahedral symmetry and its triangulation number is huge (T=1179). One curious thing is that, even though it has this huge triangulation number, the vertex can still be observed. It’s special because it has some machinery to produce energy, but it doesn’t have the machinery to produce proteins. It has a special structure in one side called stargate.

Question 41

In what depends the neutralization?

Answer 41

The neutralization will depend on the number of antibodies and the time of incubation.

Question 42

Which are the mechanisms of neutrlization?

Answer 42

1. By presentation / agglutination / agglomeration.
2. Preventing the binding of the virus to the receptor.
3. Preventing the encapsidation of the virus

Question 43

Which are the features about rinovirus?

Answer 43

This virus belongs to the picornavirus family. They cause colds. There are different serotypes.

Question 44

What is a serotype?

Answer 44

Is a virus that has certain features that are recognized by certain antibodies that are not able to recognize any other features from another virus.

Question 45

Are all of these serotypes able to recognise the same receptor?

Answer 45

all of these serotypes are able to recognize the same receptor, which is called “canyon”.

Question 46

Name a virus that has the fourth type of symmetry.

Answer 46

One example of a virus that has this type of symmetry is poxvirus.

Question 47

Name a virus that can infect even through eliminating the membrane (envelope) using alcohol

Answer 47

poxviruses. Even though the membrane of the poxvirus is removed, it’s still able to infect.