9.23.2022. + 9.26.2022. Study Questions

Question 1

How do viruses attach to host cells? (2)

Answer 1

1. phage: tail fibers
2. animal viruses: spikes

Question 2

How is the penetration step in the replication of phages different from that of animal viruses?

Question 3

How does a temperate phage differ from a lytic phage?

Answer 3

T: doesn’t necessarily lyse
L: lyses the host

Question 4

What would be the consequence if a temperate phage lost the ability to synthesize a repressor?

Answer 4

productive infection, like in the case of phage induction

Question 5

Describe why phages are important to humans (2)

Answer 5

1. they can control the spread of bacteria during storage, like we talked about in class with processed meats
2. phages are also being looked into as an option to treat bacterial infections in humans.

Question 6

What is lysogenic conversion?

Answer 6

change in phenotype of a lysogen as a consequence of the specific prophage it carries

Question 7

How are phages grown in the lab?

Answer 7

plaque assays

Question 8

What is reverse transcriptase?

Answer 8

enzyme that synthesizes DNA using RNA as a template

Question 9

Why are virally-encoded polymerases significant medically?

Answer 9

they can be used as a target for antiviral drugs

Question 10

What is a retrovirus?

Answer 10

have a (+)RNA genome and carry reverse transcriptase within the virion

Question 11

Which group of viruses need to carry their own polymerase within the virion? Why?

Answer 11

ss(-)RNA and dsRNA

Question 12

How does an enveloped virus acquire the envelope?

Answer 12

via budding

Question 13

Review animal viral replication cycle steps for each type of virus from attachment to release

Question 14

Describe two ways to quantitate animal viruses

Answer 14

1. acute
2. persistant

Question 15

What are two outcomes from a temperate phage?

Answer 15

a bacteriophage that can either
1. direct a productive infection that leads to host cell lysis or
2. remain silent within the host as a prophage (phage DNA) that replicates along with the host cell genome.

Question 16

What is a prophage?

Answer 16

integrated phage DNA

Question 17

Describe the relationship between temperate phages and prophages

Answer 17

latent form of a temperate phage; the phage DNA has generally been inserted into the host’s chromosome.

Question 18

what is a lysogen?

Answer 18

bacterial cell that is containing the prophage

Question 19

how do phages attach to cells?

Answer 19

tail fibers

Question 20

how do animal viruses attach to host cells?

Answer 20

spikes

Question 21

what is an example of lysogenic conversion?

Answer 21

only strains of Corynebacterium diphtheriae that are lysogenic for a certain phage can synthesize the toxin that causes diphtheria.

Question 22

if a toxin is encoded exclusively by phage genes…

Answer 22

then only bacterial strains that carry the prophage will synthesize the toxin

Question 23

what group of viruses encodes reverse transcriptase?

Answer 23

reverse transcribing viruses

Question 24

what happens in normal transcription vs. reverse transcription?

Answer 24

normal: RNA is synthesized from DNA template
reverse; DNA is synthesized from an RNA template

Question 25

what is an acute virus?

Answer 25

sudden onset of symptoms, short duration

Question 26

what is a persistent virus?

Answer 26

long duration, often without causing symptoms

Question 27

what are the two types of persistent viruses?

Answer 27

chronic and latent