Introduction to Viruses

Question 1

-What 3 structures can viruses take?

Answer 1

• icosahedral( 20 faces, each of which is an equilateral triangle)
• Helical (protein binds around DNA/RNA in a helical fashion
• Complex (neither icosahedral or helical)

Question 2

What is meant by viruses being obligate intracellular pathogens?

Answer 2

Can only replicate inside host cell

Question 3

What is meant by tissue tropism?

Answer 3

most viruses have a specific host range and only infect specific host cell types

Question 4

How can virus families be classified? (4)

Answer 4

• virion shape/symmetry
• presence/absence of envelope
• genome structure
• mode of replication

Question 5

What structures make up a virion? (5)

Answer 5

• lipid envelope
• nucleic acid
• spike projections
• virion associated polymerase
• protein capsid

Question 6

What steps are involved in virus replication? (7)

Answer 6

• attachment
• uncoating
• replication of genomic nucleic acid
• protein synthesis
• virion assembly
• budding and release
• maturation

Question 7

How can viruses be transmitted? (9)

Answer 7

• blood-borne
• sexual
• vertical
• faecal-oral
• droplet
• airborne
• close contact
• vector-borne
• zoonotic

Question 8

What is the host range for smallpox and measles?

Answer 8

only infect humans

Question 9

What can coinfection of human and animal/bird strain in one organism lead to?

Answer 9

recombination and generation of a new strain

Question 10

What are 4 consequences of viral infection?

Answer 10

• clearance of virus (with no,short or long term immunity)
• chronic infection
• latent infection
• transformation (long term infection with altered cellular gene expression)

Question 11

What kind of immunity is involved in hepatitis C?

Answer 11

no lasting immunity

Question 12

What kind of immunity is involved in measles?

Answer 12

long term immunity

Question 13

Give 3 examples of chronic infections

Answer 13

• HIV
• hepatitis B
• hepatitis C

Question 14

Give 2 examples of viruses which exhibit transformation .

Answer 14

• Epstein-Barr Virus

- Human Papillomavirus