L43: Viruses And Prions

Question 1

Viruses and respective diseases

Answer 1

*Rhinovirus: common cold
Poliovirus: polio
Varicella-zoster: chickenpox
Hepatitis B virus: Hepatitis
Mumps virus: mumps
HIV virus: AIDS
Influenza virus: influenza

Question 2

Classification of virus

Answer 2

1. DNA vs RNA vs Retroviral virus

2. Envelop vs Non-enveloped virus

Question 3

Structure of virus

Answer 3

1. Viral nucleic acids (DNA/RNA)
2. Protein Capsid
3. Envelope (may not present, from lipid bilayer of cell membrane)

Question 4

Virus replication cycle

Answer 4

1. Attachment
2. Penetration
3. Uncoating
4. Protein synthesis (transcription and translation) + nucleic acid replication
5. Assembly
6. Release

Question 5

Bacteria vs Virus

Answer 5

Virus: obligate intracellular parasites —> no need many genes / few genes
Bacteria: can be extracellular / intracellular

Question 6

DNA vs RNA vs Retroviral viral replication

Answer 6

DNA: viral DNA (ds) —> viral RNA —> viral protein
RNA:
- viral RNA (+ve sense) —> viral protein
- viral RNA (-ve sense) (by RNA dependent RNA polymerase) —> viral RNA (+ve sense) —> viral protein
Retroviral:
- viral RNA (reverse transcription) —> viral DNA —> viral mRNA —> viral protein

Question 7

Components of virus transport medium

Answer 7

1. pH buffer
2. Protein
3. Antibiotics

Question 8

Detecting antibody response

Answer 8

• need paired sera (10-14 days apart)
• test for antibody titre
• > = 4 fold increase in IgG indicate recent infection within 1-3 months

IgM: first antibody to appear in response to initial exposure to antigen
IgG: 75% of serum antibody, predominantly in secondary immune response

Question 9

What is Defective virus

Answer 9

• A virus does not encode all structural proteins required for viral replication
• Need a helper virus to provide key genes to complete replication cycle

Question 10

What is Prion

Answer 10

• infectious protein
• causes:
  Mad Cow disease (Bovine Spongioform Encephalopathy)
  Creutzfeldt-Jakob disease (CJD)