2. Viruses: Chapter 13 (and a bit of Chapter 8) (Part 2)

Question 1

what is lysogenic conversion?

Answer 1

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

Question 2

what is a prophage?

Answer 2

integrated phage DNA

Question 3

what are the two consequences of lysogeny?

Answer 3

immunity to superinfection, lysogenic conversion

Question 4

what is immunity of lysogen?

Answer 4

the blocking of an additional infection of a lysogen by the same type of phage. why? the repressor that maintains the prophage in the integrated state will also bind to the operator on incoming phage DNA.

meaning, if another lambda phage injects its DNA into a lambda lysogen, that DNA will not be expressed. different from human immunity.

Question 5

what is a lysogen?

Answer 5

bacterium that carries phage DNA (a prophage integrated into its genome)

Question 6

describe the role of repressors in maintaining lysogeny

Answer 6

whether the prophage persists, or the lytic cycle begins depends on repressors. the repressor prevents expression of the gene required for excision, and is therefore essential for maintaining the lysogenic (latent) state.

Question 7

describe a restriction-modification system.
“restriction,” meaning?
“modification,” meaning?

Answer 7

uses restriction enzymes to defend against invading foreign DNA

modification enzymes methylate host DNA to protect it

Question 8

connect methylation status to degradation status

Answer 8

host DNA is methylated so it doesn’t get degraded
unmethylated DNA gets degraded, methylated DNA does not

Question 9

what are the three bacterial defenses that we learnt/learned in class?

Answer 9

1. masking receptors using capsules
2. restriction modification systems
3. CRISPR

Question 10

what can capsules be used for in bacterial defenses?

Answer 10

masking receptors

Question 11

what is CRISPR?

Answer 11

how i like my fried chicken. infection memory/library to be able to develop immunity and respond quicker and more effectively the second time.

Question 12

what is a plaque assay?
what can it be used for?

Answer 12

method used to count the number of viral particles that are present in a sample

Question 13

describe the animal virus life cycle (6)

Answer 13

attachment
penetration
synthesis of viral proteins
replication
synthesis
release

Question 14

describe the attachment stage of the animal virus life cycle

Answer 14

use spikes to bind to receptors

Question 15

describe the penetration stage of the animal virus life cycle

Answer 15

happens two ways: endocytosis (AERU) or membrane fusion (AMNU)

Question 16

describe the synthesis of viral proteins stage of the animal virus life cycle (2)

Answer 16

• expression of viral genes to produce structural and catalytic proteins
• synthesis of multiple copies of the viral genome

Question 17

describe the release stage of the animal virus life cycle

Answer 17

virus is released from host cell through budding

Question 18

what is a reverse transcribing virus?

Answer 18

they encode reverse transcriptase

Question 19

what is reverse transcriptase?

Answer 19

protein which makes DNA from an RNA template, and is encoded by reverse transcribing viruses

Question 20

what is a retrovirus?

Answer 20

have mRNA genome and reverse transcriptase, make one strand of DNA which is eventually used to make two strands and integrate irremovably from the host genome.

group of viruses that have a single-stranded RNA genome; their enzyme reverse transcriptase synthesizes a DNA copy that is then integrated into the host cell chromosome.

Question 21

replicase =

Answer 21

RNA dependent RNA polymerase

Question 22

RNA dependent RNA polymerase =

Answer 22

replicase

Question 23

which viruses carry their own replicase?

Answer 23

-RNA and dsRNA

Question 24

what do reverse transcriptase and replicase have in common? they are… which makes them have…

Answer 24

error prone
higher mutation rates and evolve faster

Question 25

_____ ________ and _______ are error prone. These viruses have higher mutation rates and evolve faster.

Answer 25

Reverse transcriptase
Replicase