Viruses

Question 1

What are Viruses ?

Answer 1

Infectious agents that require a host in order to replicate

Question 2

What do ‘obligate parasites’ lack ?

Answer 2

The mechanism for metabolic energy/protein synthesis

Question 3

How are viruses classified ?

Answer 3

1) By morphology
2) Chemical composition
3) Mode of replication

Question 4

What are virons (virus particles) assembled from ?

Answer 4

They’re assembled from pre-formed components

Question 5

Name the pre-formed components virons are assembled from ?

Answer 5

1) Genome - which contains either DNA or RNA
2) Protein shell (Capsid) - together w/genome = Nucleocapsid
3) Membrane envelope
4) Outer layer (for protection and for recognition sites of host cells)

Question 6

Give an example of a ‘non-serious’ virus and the infection it causes

Answer 6

• Rhinovirus - causes a cold

Question 7

Give an example of ‘serious’ viruses

Answer 7

• Enteroviruses

Question 8

Give examples of sever diseases caused by viruses

Answer 8

1) Rabies

2) Ebola

Question 9

What is the importance of the Capsid of a virus ?

Answer 9

It allows for classification of a virus

Question 10

Name 3 classes of Viruses ?

Answer 10

1) Helical
2) Icosahedral (formed by capsomers)
3) Complex

Question 11

What is meant by a Naked virus ?

Answer 11

Virus that has a capsid only and no envelope

Question 12

What is meant by an Enveloped virus and what is the envelope made out of ?

Answer 12

The capsid is surrounded by an envelope which is made out of Lipids and proteins

Question 13

Name an example of complex virus

Answer 13

bacteriophage T4

Question 14

Give 3 functions of the the Capsid

Answer 14

1) Protection -from the hosts acid and from protein-digesting enzymes
2) Assists in binding and penetrating host cell
3) Stimulates the host’s immune system

Question 15

The nucleocapsid of an enveloped virus is more flexible than that of a naked virus. TRUE or FALSE ?

Answer 15

TRUE

Question 16

Envelope spikes (glycoproteins) consist of carbohydates and protein complexes which are used in attachment to host cell. TRUE or FALSE ?

Answer 16

TRUE

Question 17

Virus DNA or RNA can be double (ds) or single stranded (ss). TRUE or FALSE ?

Answer 17

TRUE

Question 18

ssRNA further divides into Positive and Negative polarity. TRUE or FALSE ?

Answer 18

TRUE

Question 19

DNA viruses fall into class 1, 2 AND 7. TRUE or FALSE ?

Answer 19

TRUE

Question 20

RNA viruses fall into class 3-6. TRUE or FALSE ?

Answer 20

TRUE

Question 21

RNA viruses show very rapid rates of mutation. TRUE or FALSE ? and why ?

Answer 21

TRUE, because they DO NOT have proof-reading abilties

Question 22

DNA polymerases possess proof reading abilities, therefore less mutations and evolve less rapidly. TRUE or FALSE ?

Answer 22

TRUE

Question 23

Give 2 mechanisms Viruses may use to evade detection ?

Answer 23

1) Change their antigens, therefore they’re not recognised

2) Generalised immune response

Question 24

How many stages of the Viral cycle are there ? Name them.

Answer 24

6

1) Attachment
2) Penetration
3) Uncoating
4) Genome replication
5) Assembly of virion particle
6) Release

Question 25

Many viral infections are not silent. TRUE OR FALSE?

Answer 25

FALSE

Question 26

What does the outer layer of a virus do?

Answer 26

It provides protection and it is the recognition site for host cells

Question 27

How are viruses classified?

Answer 27

By morphology and chemical composition/mode of replication

Question 28

The capsomere does not forms the main building blocks of isohedral structure. TRUE OR FALSE?

Answer 28

FALSE

Question 29

Icosahedral virus can be enveloped (with a capsid) or naked (without a capsid). TRUE OR FALSE?

Answer 29

TRUE

Question 30

Give an example of a non enveloped icosahedral virus?

Answer 30

Adenovirus

Question 31

Helical viruses can be enveloped or naked. TRUE OR FALSE?

Answer 31

TRUE

Question 32

What does a helical virus assemble into together with viral nucleic acid?

Answer 32

Helical structure

Question 33

Give an example of a non enveloped and non enveloped helical virus?

Answer 33

non -Ebola | Influenza is enveloped

Question 34

What are complex viruses made up of?

Answer 34

Repeated units of a single polypeptide protomer

Question 35

What structures does Complex viruses together with nucleic acid form?

Answer 35

Helical structure

Question 36

What is enveloped spike involved in?

Answer 36

Recognition and attachment

Question 37

What are the mechanism that viruses used to avoid detection?

Answer 37

1. Changing their antigens, so not recognised | 2. Generalises immune suppression

Question 38

What does reverse transcriptase produce?

Answer 38

It uses a single stranded RNA genome to create a double stranded DNA

Question 39

Reverse transcriptase , involves DNA to RNA. TRUE OR FALSE?

Answer 39

TRUE

Question 40

What occurs during the initial contact of a viral infection?

Answer 40

Glycoproteins on the surface bind to cell surface

Question 41

What are the two different phases during initial contact of viral infection?

Answer 41

Reversible phase - electrostatic repulsion reduced | Irreversible phase - initiation of viral penetration

Question 42

What two mechanisms are initiated during the conformational changes of the anti-receptor - receptor complex?

Answer 42

Endocytosis (cell membrane is engulfs virus) | Fusion of viral envelopes and cell membrane (releases capsid into cytosol)

Question 43

What are the two main routes of virion release?

Answer 43

Lysis | Budding

Question 44

How are enveloped and non enveloped viruses released?

Answer 44

Enveloped - By budding | Non enveloped - By lysis

Question 45

What does Hepatitis cause?

Answer 45

Inflammation of the liver

Question 46

Hepatitis A - highly contagious, contamination is via water, it is a mild infection and can be self resolving. TRUE OR FALSE?

Answer 46

TRUE

Question 47

Hepatitis B and C does not spread through body fluid and can cause long term disease. TRUE or FALSE?

Answer 47

FALSE

Question 48

HBV is a small DNA virus that replicates through an RNA intermediate and can integrated into host genome. TRUE OR FALSE?

Answer 48

TRUE

Question 49

The synthesis of influenza mRNAs and replication occurs in the nucleus. TRUE OR FALSE?

Answer 49

TRUE

Question 50

For normal RNA viruses where does replication and synthesis occur?

Answer 50

In the cytoplasm

Question 51

What are the two subtypes that influenza A is divided into?

Answer 51

Hemagglutin (H) | Neuraminidase (N)

Question 52

What are the stages of HIV?

Answer 52

Acute infection - HIV replicates rapidly, CD4 count drops Clinical latency - Virus replication much slower/immune system becomes compromised due to low CD4 count AIDS - acquired immunodeficiency syndrome / immune system severely compromised / vulnerable to infections and infection related cancers.

Question 53

Some viruses induce (bring about) cancer. TRUE OR FALSE?

Answer 53

TRUE

Question 54

Give an example of an antiviral therapy

Answer 54

Vaccination