lecture 32

Question 1

what is a virus?

Answer 1

• acellular, “borrowed life”
• Rely completely on biosynthetic machinery of infected cell to multiply
• infect all types of cells
• most abundant biological entities

Question 2

what are viruses made of?

Answer 2

• genetic material (ss or ds, RNA or DNA)
• capsid, protein coat that surrounds and protects genetic material
• sometimes has envelope of lipids, surrounds the protein coat when they are outside a
  cell and facilities entry into the cell

Question 3

what are capsids?

Answer 3

• made of capsomers
• Capsomers = subunit of the capsid arranged in a precise
  and highly repetitive pattern around the nucleic acid
• 3 types : helical, icosahedral, complex

Question 4

what are viral genomes like?

Answer 4

• made of nucleic acid (ss or ds, RNA or DNA)
• 3 shapes possible : linear, circular, segmented

Question 5

what are bacteriophages?

Answer 5

viruses that digest bacteria

Question 6

what is the lytic cycle of bacteriophage infection?

Answer 6

1. attach
2. penetrate + inject genetic info
3. uncoat
4. genome replication + expression
5. assembly
6. release, destroys bacteria at the same time

Question 7

how does mammalian virus cell replication work?

Answer 7

1. attach via receptor
2. penetrate, move into cell
3. uncoat
4. genome replication and gene expression
5. assembly
6. release, cell can remain intact, may use exocytosis

Question 8

what makes SARS-CoV-2 good at evolving and making new strains?

Answer 8

it has limited proofreading, so makes many mistakes and mutants

Question 9

what is the “spike” used for on viruses?

Answer 9

• critical for attachment + entry into host cell
• major target for neutralizing immunity
• virus must bind to receptor to infect
• vaccines target spike