Viruses Part A

Question 1

What are viruses?

Answer 1

Acellular organisms that require a host to replicate.

Question 2

What is expected to be found in every virus?

Answer 2

Nucleic acid and a capsid

Question 3

What is a nucleocapsid?

Answer 3

The nucleic acid surrounded by a capsid

Question 4

Polymerase

Answer 4

Help transcribe DNA when virus is infecting

Question 5

Protease

Answer 5

Help virus take over the host cell

Question 6

What are the possible capsid structures?

Answer 6

Icosahedral and Helical

Question 7

What are the building blocks/subunits of an icosahedral capsid?

Answer 7

Capsomers

Question 8

Does Influenza virus have an envelope?

Answer 8

Yes, and it has spikes containing 2 different proteins: Hemagglutinin (HA) and Neuraminidase (NA)

Question 9

What does Hemagglutinin (HA) do?

Answer 9

It causes aggregation/clumping when RBC are present

Question 10

What does Neuraminidase (NA) do?

Answer 10

It is a protease that helps the virus leave the host cell when replication is finished

Question 11

What type of nucleocapsid does Influenza Virus have?

Answer 11

Helical nucleocapsid

Question 12

What are the general stages of Viral Replication?

Answer 12

1. Adsorption
2. Entry
3. Synthesis
4. Assembly
5. Release

Question 13

What cycle is a temperate phage connected to?

Answer 13

Lysogenic cycle

Question 14

What cycle are virulent phages and temperate phages connected to?

Answer 14

Lytic cycle

Question 15

Steps of the Lysogenic cycle

Answer 15

1. The phage DNA integrates into host chromosome, where the virus is not actively replicating
2. The prophage DNA is copied when the cell divides. No viral proteins are being made
3. Exposure to a stress such as UV light triggers excision from the host chromosome
4. The viral DNA reaches a resting state, then commits to the lytic cycle

Question 16

Steps of the Lytic cycle

Answer 16

1. Phage attaches to the host and injects its DNA into the cytoplasm
2. The phage DNA directs the synthesis of many new phages
3. Cell lysis and releases the new phages (now a virulent phage)
4. The new phages can bind to other bacterial cells

Question 17

Viral steps that cause an acute infection

Answer 17

1. Adsorption to the host
2. Penetration
3. Rapid multiplication
4. Cell death and viral release

Question 18

Viral steps that cause a latent infection

Answer 18

1. Adsorption to the host
2. Penetration
3. Virus is present, but does not harm the host
4. Activation (Optional)
5. Cell death and viral release (triggering an acute infection)

Question 19

Viral steps that cause a chronic infection

Answer 19

1. Adsorption to the host
2. Penetration
3. Slow release of virus without cell death

Question 20

Viral steps that cause transformation into malignant cell (cancer)

Answer 20

1. Adsorption to the host
2. Penetration
3. Activation of host proto-oncogene or insertion of oncogene

Question 21

What was considered when creating viral taxonomy?

Answer 21

Evolutionary relatedness of:

• Nucleic acid type (DNA or RNA, ss or ds)
• Presence/absence of envelope
• Capsid symmetry (icosahedral or helical)
• Dimensions of the virion & capsid

Question 22

What is the Baltimore System based on?

Answer 22

• Viral genome (DNA or RNA, ss or ds, + or -)

- Process used to synthesize mRNA

Question 23

How does a double-stranded (ds) DNA virus genome replicate?

Answer 23

dsDNA –> dsDNA

Question 24

How does a double-stranded (ds) DNA virus mRNA synthesize?

Answer 24

dsDNA –> mRNA

Question 25

How does a single-stranded (ss) DNA virus genome replicate?

Answer 25

ssDNA –> dsDNA –> ssDNA

Question 26

How does a single-stranded (ss) DNA virus mRNA synthesize?

Answer 26

ssDNA –> dsDNA –> mRNA

Question 27

How does a double-stranded (ds) RNA virus genome replicate?

Answer 27

dsRNA –> ssRNA –> dsRNA

Question 28

How does a double-stranded (ds) RNA virus mRNA synthesize?

Answer 28

dsRNA –> mRNA

Question 29

How does a plus-strand RNA (+RNA) virus genome replicate?

Answer 29

+RNA –> -RNA –> +RNA

Question 30

How does plus-stand RNA (+RNA) virus mRNA synthesize?

Answer 30

+RNA = mRNA –> -RNA –> mRNA

Question 31

How does a negative-strand RNA (-RNA) virus genome replicate?

Answer 31

-RNA –> +RNA –> -RNA

Question 32

How does a negative-strand RNA (-RNA) virus mRNA synthesize?

Answer 32

-RNA –> mRNA

Question 33

How does a retrovirus genome replicate?

Answer 33

ssRNA –> dsDNA –> ssRNA

Question 34

How does a retrovirus mRNA synthesize?

Answer 34

ssRNA –> dsDNA –> mRNA

Question 35

How does a reverse transcribing DNA virus genome replicate?

Answer 35

dsDNA –> ssRNA –> dsDNA

Question 36

How does a reverse transcribing DNA virus mRNA synthesize?

Answer 36

dsDNA –> mRNA