Virology Final Part 2

Question 1

How are viruses assembled?

Answer 1

The components have an affinity for each other and are assembled into units of protein shell and then pre-virion structures; the genome is inserted at some point— then released from the host cell

Question 2

What is the difference between naked virus egress and enveloped?

Answer 2

Naked: cell lyses, dies, all progeny egress at once
Enveloped: virus buds out and virus production continues

Question 3

Why are capsids made using subunit construction?

Answer 3

1. Genetic economy (less genetic material is required if the protein unit repeats)
2. Misfolding proteins is very common
3. Must be able to be both stable and unstable when necessary

Question 4

What are some features of virus assembly that occur in some but not all viruses?

Answer 4

Acquisition of the envelop and virion maturation

Question 5

How are virus genomes selected from all of the nucleic acid that might be present in an infected cell?

Answer 5

Specific nucleic acid—protein interactions

Question 6

How does the capsid find the viral genome to package it

Answer 6

• specific sequence (ss or ds)

- presence of secondary structures in the genome (ss genomes)

Question 7

How do the packaging mechanisms overcome the repulsion of negatively charged phosphate groups in the nucleic acid?

Answer 7

• polyamines (cations with genome)
• small basic proteins (encoded)
• cells histones

Question 8

How do viruses acquire envelopes?

Answer 8

Budding through the cell membrane, golgi or nuclear membrane

Question 9

What is the structure of an envelope protein?

Answer 9

• large glycosylated external domain, hydrophobic trans-membrane anchor (20aa’s), short cytoplasmic tail

Question 10

What is the purpose of external proteins?

Answer 10

Attachment to the host cell/fusion of envelope and membrane

Question 11

What is the purpose of the cytoplasmic tail in a spike protein?

Answer 11

Connects to internal virus structures

Question 12

What determines the shape of an envelope?

Answer 12

The shape of the capsid

Question 13

What is the function of a matrix protein?

Answer 13

Bridge to link the nucleocapsid to the envelope

Question 14

What are some non-structural proteins that viruses encode?

Answer 14

RDRP, RT, Proteases, primers, ion channels, proteins that interfere with host immune responses

Question 15

What happens in capsid maturation?

Answer 15

• change of shape of the capsid
• sealing of the genome in the capsid
• release of proteins needed for the next infectious cycle

Question 16

What is the foundation of the Baltimore system?

Answer 16

• viruses need to make proteins, and to do this they need to make mRNA
• they are grouped by how they make their mRNA

Question 17

What are the three ways that cells can respond to virus infection?

Answer 17

• no apparent change
• cytopathic effect (rounded, inclusion bodies, fusion) and death
• loss of growth control (transformation)

Question 18

What are the methods of cultivating viruses?

Answer 18

For initial isolation: primary cell culture (need to be teased apart or dispersed with protease enzymes)
For vaccine: continuous culture, embryonated egg

Question 19

What is poliomyelitis?

Answer 19

Inflammation of grey matter of the spinal chord

Question 20

What is abortive polio?

Answer 20

• asymptomatic
• cold-like symptoms
• 95% of infections

Question 21

What is non-paralytic polio?

Answer 21

• “influenza” like symptoms
• back pain, muscle stiffness
• headache, fever
  1-2 weeks

Question 22

What is paralytic polio?

Answer 22

• 5-7 days before symptoms
• abnormal sensation
• muscle cramps/weakness
• sensitivity to touch
• difficulty breathing

Question 23

What is PPS?

Answer 23

Muscle weakness 30-40 years post infection; stress over years of depending on fewer neurons