Viral Replication

Question 1

How do you study viral replication

Answer 1

In-vitro

Question 2

Study of viruses in-vivo is what?

Answer 2

Study of viral pathogenesis

Question 3

What kind of curve to scientists develop to study viruses

Answer 3

One-step growth curve

Question 4

In one step growth curve, what does ‘total virus mean’

Answer 4

Input virus (attached and unattached ) and progeny virus (intra- and extracellular)

Question 5

In one step growth curve, what does ‘total cell free virus’ mean?

Answer 5

Input virus (unattached) and progeny (extracellular)

Question 6

In one step growth curve, what does ‘total cell-associated virus’ mean?

Answer 6

Input virus (attached, not penetrated) and progeny (intracellular)

Question 7

For viruses that dont grow in cell cultures, how do you study them?

Answer 7

Use infectious clones

Question 8

What is the eclipse period

Answer 8

The period after viral penetration and virus releases genome, in which the progeny is not detectable

2-12 hours

Question 9

T/F the eclipse period is the same as the incubation period

Answer 9

False!

Question 10

What are some early products from viral replication (3)

Answer 10

1. Proteins that shut down cell processes
2. Proteins that regulate expression of viral genome
3. Enzymes requires for replication of viral nucleic acid

Question 11

What are some late products of viral replication (1)

Answer 11

Structural proteins

Question 12

Where does DNA viral replication take place and which enzymes does it use

Answer 12

Nucleus

DdRp (DNA dependent RNA polymerase)

Question 13

Where does RNA viral replication take place and which enzymes does it use

Answer 13

Cytoplasm

1. Retrotranscriptases
2. RdRp (RNA viruses)
3. DdRp (DNA viruses that replicate in cytoplasm)

Question 14

What are cellular enzymes for replication (2)

Answer 14

DdDp

DdRp

Question 15

What are viral enzymes for replication (3)

Answer 15

1. Retrotranscripatse
2. RdRp
3. DdRp

Question 16

Steps of viral replication

Answer 16

1. Attachment
2. Penetration (membrane fusion/endocytosis)
3. Uncoating
4. Transcription/Translation
5. Processing
6. Assembly/release

Question 17

How do enveloped viruses penetrate

Answer 17

Membrane fusion

Question 18

How do naked viruses penetrate

Answer 18

Receptor mediated endocytosis

Question 19

If DNA viruses un-coat in the cytoplasm, what do they require

Answer 19

Chaperone proteins

Question 20

Describe ss+ RNA viral transcription/translation

Answer 20

They bind directly to ribosome and start TRANSLATION

Question 21

Describe ss- RNA viral transcription/translation

Answer 21

Transcription must occur first – cant just fit onto ribosomes

They carry own enzymes (the RdRp protein)

Question 22

Retroviruses have two copies of ________ and replicate through a _____ intermediate

Answer 22

ss+ RNA

DNA

Question 23

Which enzyme do retroviruses use? What is the primer?

Answer 23

Reverse transcriptase

tRNA is the primer

Question 24

Functions of LTR (2)

Answer 24

1. Integration to host genome

2. Strong promoter (oncogenic)

Question 25

Steps of retrovirus replication

Answer 25

1. Start with two copies of ss+ RNA 2. Reverse transcriptase uses tRNA as a primer 3. RNA:DNA hybrid formed 4. Copies of ss- DNA form a linear double stranded DNA, containing an LTR at each end 5. ds DNA integrates into cellular chromosome as proviral DNA 6. Further transcription of viral RNA occurs through proviral DNA

Question 26

Which viruses undergo translation first (7)

Answer 26

ss+ RNA viruses CAP-FACT 1. Calici 2. Astro 3. Picorna 4. Flavi 5. Arteri 6. Corona 7. Toga

Question 27

Which viruses undergo transcription first (8)

Answer 27

ss- RNA viruses ds RNA segmented viruses RRR- BB- FOAP 1. Rhabdo 2. Reo 3. Retro 4. Arena 5. Birna 6. Bunya 7. Orthomyxo 8. Paramyxo 9. Filo

Question 28

Which ss+ RNA virus undergoes translation first

Answer 28

Retrovirus

Question 29

How are naked viruses released post-replication

Answer 29

Accumulate in nucleus/cytoplasm until cell lysis occurs

Question 30

How are enveloped viruses release post-replication

Answer 30

Exoctyosis

Question 31

What is a susceptible cell

Answer 31

Virus can enter

Question 32

What is a permissive cell

Answer 32

Virus can replicate

Question 33

Which enzyme does poxvirus for reproduction

Answer 33

DdRp - in cytoplasm