Viral Infection

Question 1

What is a virus

Answer 1

Small infectious obligate intracellular parasite

Question 2

Are virus particles living

Answer 2

No

Question 3

Can viruses reproduce by themselves

Answer 3

No

Question 4

What do virus particles needs to reproduce

Answer 4

A host

Question 5

What do all viruses make that need a host for

Answer 5

Viruses make mrna so need to the hosts ribosome that can translate it

Question 6

What is the structural features of a virus

Answer 6

Dna or rna
Capsid protein
Glycoproteins on the surface

Question 7

What is the dna/rna + capsid protein called

Answer 7

Nucelocapsid i.e naked capsid virus

Question 8

What does the naked capsid virus have for it to become an enveloped virus

Answer 8

Lipid membrane

Glycoproteins

Question 9

What are the 2 types of capsid assembly that can occur in a virus

Answer 9

Helical symmetry

Icosahedral symmetry

Question 10

What is a helical symmetry

Answer 10

Nucleic acid arranged in a helix

Question 11

What is a icosahedral symmetry

Answer 11

Protein subunits assemble in to a symmetric shell that covers the nucleic acid containing core

Question 12

Which classification do we use to classify viruses

Answer 12

Blatimore classification

Question 13

What is the baltimore classification based on

Answer 13

1. Type and structure of the viral nucelic acid and stratergy used to replicate
2. Type of symmetry: helical or icosahedral
3. Presence or absenc of a lipid envelope

Question 14

Decribe the cycle of a virus and how it infects

Answer 14

1. Virus gets to a cell and attached by lock and key effect
2. Virus penetrates into the cell and is engulfed by endocytosis
3. Virus dissambles (uncoates) to relesae the viral genome and viral enzymes i.e viral contents
4. Viral genome (dna or rna) is transcribed to form mrna
5. Mrna is translated to viral proteins
6. Virla genome also replicates
7. Viral proteins and genome assembly togethether to form the virus
8. Virus is released

Question 15

What is a key feature of retrovirus

Answer 15

Retrovirus bring reverse transcriptase enzyme with it do the rna is turned into double stranded dna
The double stranded dna can travel to the nucleus and become integrated into the host dna
When the host dna is transcripted it makes the retrovirus too

Question 16

What is latent infection

Answer 16

When the virus infects a cell goes to sleep and can become reacitvated to cause infection again

Question 17

Name a virus that has latency

Answer 17

Herpes virus

Question 18

Explain how the herpes vrius presents with latency

Answer 18

1. Herpes virus infection initially as chickenpox
2. The virus moves to the dorsal root ganglion where it remains latent
3. In adulthood when the immune system depresses the herpes virus reactivates and causes shingles

Question 19

What type of cancer can HPV cause

Answer 19

Cervical cancer

Question 20

What are the 2 ways the immune system can kill viruses

Answer 20

1. Cell mediated response

2. Humoral response

Question 21

What is the cell mediated response

Answer 21

1. The infected cell displays the viral antigen on the MHC complex
2. T cells make contact with the infected cell and release granules
3. Granule induce cell to self destruct so the virus cant replicate

Question 22

What is the humoral response

Answer 22

1. The antibody coats the free virus
2. Virus therefore cannot infect the cell
3. The virus coated with antibodies is destroyed by neutrophils

Question 23

How can we detect viral infection

Answer 23

• viral culture
• electron microscopy
• serology
• PCR: testing for the genetic material of the virus e.g dna or rna

Question 24

What are the mechanism of action of antiviral drugs

Answer 24

Prevent the entry of virus into the cell
Prevent reverse transcriptase
Prevent the integration of viral dna into the cell

Question 25

What are bacteriophages

Answer 25

Virsues that can infect bacteria