Lecture 6

Question 1

What is a virus?

Answer 1

submicroscopic, parasitic, filterable agent with nucleic acid in a protein coat
- intracellular parasites

Question 2

What are specific characteristics of viruses?

Answer 2

• multiply inside living cells through synthesis of the cell (synthesis of specialized structures that can transfer the viral nucleic acid)
• contain single type of nucleic acid and protein coat that surrounds nucleic acid
• no ribosomes
• no ATP-generating mechanism

Question 3

What is a host range?

Answer 3

spectrum of host cells a virus can infect

Question 4

What is cell tropism?

Answer 4

most viruses infect only specific types of cells in one host
- determined by specific host attachment sites and cellular factors

Question 5

What are bacteriophages? Where are the receptor sites?

Answer 5

viruses that infect bacteria
- receptor sites are on the cell wall of the host

Question 6

Where are receptor sites on animal cell hosts?

Answer 6

plasma membrane

Question 7

What does viral size depend on?

Answer 7

• electron microscopy & hydrogen bonds
• ratios

Question 8

What is virion? What structures are included?

Answer 8

complete, fully developed viral particle
- nucleic acid
- capsid
- envelope
- spikes

Question 9

What is the general morphology of virions?

Answer 9

• helical viruses
• polyhedral viruses
• enveloped viruses
• complex viruses

Question 10

What is nucleic acid?

Answer 10

DNA or RNA
- linear or circular

Question 11

What are nonenveloped polyhedral viruses?

Answer 11

capsid protects nucleic acid

Question 12

What are polyhedral viruses? Give some examples.

Answer 12

Capsid shaped like icosahedron
- animal, plant, bacterial viruses

Question 13

What is a capsid?

Answer 13

protein coat made of capsomeres (subunits)

Question 14

What is a helical virus?

Answer 14

• helical virus
• nucleic acid inside hollow, cylindrical capsid
• long rods
• rigid or flexible
• rabies and ebola

Question 15

What is an envelope?

Answer 15

• lipid, proteins, carbohydrates
• coating on some viruses from animal cells
• envelope determined by nucleic acid and materials from host cell

Question 16

What are spikes?

Answer 16

• projections from outer surface
• carbohydrate-protein complexes
• attaches to host cell for identification

Question 17

What is an example of a complex virus?

Answer 17

bacteriophage

Question 18

What are the main components of a bacteriophage?

Answer 18

• capsid
• sheath
• pin
• baseplate
• tail fiber

Question 19

What is the function of the sheath?

Answer 19

• responsible for injecting viral genetic material into host
• acts like a spring

Question 20

What is the function of the pin?

Answer 20

stabilizing element
- initial attachment of bacteriophage
- connects bacterial surface

Question 21

What is the function of the baseplate?

Answer 21

anchors tail fibers and pin
- primary attachment site for bacteriophage to the bacterial cell

Question 22

What is the function of the tail fiber?

Answer 22

appendages that help attach a virus to a host cell
- binds to cell wall

Question 23

What is the taxonomy of viruses?

Answer 23

genus: -virus
family: -viridae
order: -ales

Question 24

What does a virus need to replicate?

Answer 24

a host cell

Question 25

What is the easiest host?

Answer 25

bacteriophages

Question 26

What do bacteriophages form in laboratory? What do they represent?

Answer 26

grows plaques
- corresponds to a single virus

Question 27

How do you grow animal viruses in laboratory?

Answer 27

• in living animals
• in embryonated eggs
• in cell cultures

Question 28

What are 3 ways we can identify viruses?

Answer 28

• cytopathic effects
• serological tests
• nucleic acids