Midterm 2 - Notes 4 (Part 2)

Question 1

What do genus names end in?

Answer 1

-virus

Question 2

What do family names end in?

Answer 2

-viridae

Question 3

What do order names end with?

Answer 3

-ales

Question 4

Viral species

Answer 4

A group of viruses sharing the same genetic information and ecological niche (host)

Question 5

Where must viruses be grown in?

Answer 5

In living cells

Question 6

Where are bacteriophages grown?

Answer 6

In bacteria

Question 7

What do bacteriophages form?

Answer 7

Plaques

Question 8

Plaques

Answer 8

Are clearing on a lawn of bacteria on the surface of agar

Question 9

What does each plaque correspond to?

Answer 9

A single virus

- plaque- forming units (PFU)

Question 10

Where do you grow animal viruses?

Answer 10

In living animal cells

Question 11

Cytopathic effect

Answer 11

Virally infected cells are detected via their deterioration

- continuous cell lines are used

Question 12

What are the 3 steps in cell cultures?

Answer 12

1. A tissue is treated with enzymes to separate the cells
2. Cells are suspended in culture medium
3. Normal cells or primary cells grow in a monolayer across the class of plastic container
   - transformed cells or continuous cell cultures do not grow in a monolayer

Question 13

Viral identification (3)

Answer 13

1. Cytopathic effects
2. Serological tests
   - western blotting
3. Nucleic acids
   - RFLPs
   - PCR (eg. herpes)

Question 14

What 2 things must happen in order for a virus to multiply?

Answer 14

1. It must invade a host cell

2. It must take over the host’s metabolic machinery

Question 15

What are the 2 cycles involved with multiplication of bacteriophages?

Answer 15

1. Lytic cycle

2. Lysogenic cycle

Question 16

Lytic cycle

Answer 16

Phage causes lysis and death of the host cell

Question 17

Lysogenic cycle (3)

Answer 17

1. Phage DNA is incorporated in the host DNA
2. Phage conversion
   - host cell inhibits new properties
3. Specialized transduction
   - when the host cell replicates its chromosomes is also replicates prophage DNA

Question 18

T-Even Bacteriophages: The Lytic Cycle stages (5)

Answer 18

1. Attachment: phage attaches by the tail fibres to the host cell
2. Penetration: phage lysozyme opens the cell wall
   - tail sheath contracts to force the tail core and DNA into the cell
3. Biosynthesis: production of phage DNA and proteins
4. Maturation: assembly of phage particles
5. Release: phage lysozyme breaks the cell wall

–> leads to assembly of the components for a new virus (eg. tail fibres)

Question 19

Lysogeny

Answer 19

Phage remains latent

Question 20

What are the 6 possible stages of lysogenic cycke stages?

Answer 20

1. Phage attaches to host cell and injects DNA
2. Phage DNA circularizes and enters lytic cycle or lysogenic cycle
   3a. New pahge DNA and proteins are synthesized and assembled into virions
   4a. Cell lyses, releasing phage virions
   3b. Phage DNA integrates within the bacterial chromosome by recombination becoming a prophage
   4b. Lysogenic bacterium reproduces normally

Question 21

Lysigenic stages

Answer 21

Is when the virus DNA is incorporated into the host cell

- will continue to replicate but may exercise and re-enter the lytic cycle

Question 22

Specialized transduction (2)

Answer 22

1. Specific bacterial genes transferred to another bacterium via a phage
2. Changes genetic properties of the bacteria

Question 23

What are the 6 stages in specialized transduction?

Answer 23

1. Prophage exists in galactose-using host
   - containing the gal gene
2. Phage genome excises, carrying with it the adjacent gal gene from the host
3. Phage matures and cell lyses, releasing phage carrying gal gene
4. Phage infects a cell that cannot utilize galactose
   - lacking gal gene
5. Along with the prophage, the bacterial lag gene becomes integrated into the new host’s DNA
6. Lysogenic cell can now metabolize galactose

Question 24

Comparing bacteriophage and animal viruses; attachment

Answer 24

B = Tail fibres attach to the cell wall proteins 
A = Attachment sites are on the plasma membrane and glycoproteins

Question 25

Comparing bacteriophage and animal viruses; Entry

Answer 25

B = Viral DNA is injected into host cell 
A = Capsid enters by receptor mediated endocytosis or fusion

Question 26

Comparing bacteriophage and animal viruses; uncoating

Answer 26

B = Not required 
A = Enzymatic removal of capsid proteins

Question 27

Comparing bacteriophage and animal viruses; biosynthesis

Answer 27

B = In cytoplasm
A = In nucleus (DNA virus) or cytoplasm (RNA virus)

Question 28

Comparing bacteriophage and animal viruses; chronic infection

Answer 28

B = Lysogeny
A = Latency: slow viral infections; cancer

Question 29

Comparing bacteriophage and animal viruses; release

Answer 29

B = Host cell is lysed
A = Enveloped viruses bud out; nonenveloped viruses rupture plasma membrane

Question 30

What are the 6 steps in multiplication of animal viruses?

Answer 30

1. Attachment: viruses attach to the cell membrane
2. Entry by receptor-mediated endocytosis or fusion
3. Uncoating by viral or host enzymes
4. Biosynthesis: production of nucleic acid and proteins
5. Maturation: nucleic acid and capsid proteins assemble
6. Release by budding (enveloped viruses) or rupture

Question 31

Where do DNA viruses replicate their DNA?

Answer 31

In the nucleus of the host using viral enzymes

Question 32

Where do DNA viruses synthesize capsid?

Answer 32

In the cytoplasm using host cell enzymes

Question 33

What are the 7 stages of replication if DNA-containing animal viruses?

Answer 33

1. Attachment: virion attaches to host cell
2. Entry and uncoating: virion enters cell, and its DNA is uncoated
3. A portion of viral DNA is transcribed, producing mRNA that encodes “early” viral proteins
4. Biosynthesis: viral DNA is replicated and some viral proteins are made
5. Late translation: capsid proteins are synthesized
6. Maturation: virions mature
7. Release: virions mature