Virus Replication

Question 1

What is a permissive cell?

Answer 1

A cell in which a virus is able to replicated

Question 2

What is a non-permissive cell?

Answer 2

Cells in which a factor or factors needed for viral replication is not present or one detrimental to viral replication is present

Question 3

What is the multiplicity of infection (MOI)?

Answer 3

Refers to number of virions that are added p/cell during infection

Question 4

The eclipse period is after uncoating and before 1st appearance of what kind of virus particle?

Answer 4

Intracellular

Question 5

The latent period is after uncoating and before 1st appearance of __________ new virus particle

Answer 5

Extracellular

Question 6

What are the 4 components of the one-step virus curve growth?

Answer 6

1. Adsorption
2. Eclipse period
3. Latent period
4. Burst size

Question 7

What is adsorption?

Answer 7

Virus attaches to and enters cells; titer of free virus in medium may actually decline

Question 8

What is burst size?

Answer 8

Number of infectious virions released per average cell

Question 9

What are the 6 steps in virus replication?

Answer 9

1. Attachment
2. Penetration
3. Uncoating
4. Synthesis of Viral components (Nucleic acid and protein)
5. Assembly and maturation
6. Release in large numbers

Question 10

T/F: Virus attachment to receptor(s) on host cells is/are very specific, like lock-key

Answer 10

True

Question 11

Attachment to host cell surface is mediated by what two interactions?

Answer 11

Interactions between virus and complimentary receptor on host cell surface

Question 12

T/F: In some cases, attachment requires an additional cell surface molecule, or co-receptor

Answer 12

True

Question 13

What are two ways non-enveloped/naked viruses penetrate and uncoat host cell?

Answer 13

1. Receptor mediated endocytosis (common)

2. Pore mediated penetration

Question 14

What are two ways enveloped viruses penetrate and uncoat host cell?

Answer 14

1. Surface membrane fusion (pH independent fusion protein)

2. Receptor mediated endocytosis (pH dependent fusion protein)

Question 15

With is another/uncommon mode of entry for viruses?

Answer 15

Antibody-mediated attachment and penetration

Question 16

What is an example of receptor mediated endocytosis for non-enveloped viruses?

Answer 16

Clathrin-mediated endocytosis

Question 17

For an enveloped virus, surface membrane fusion occurs directly on host cell surface and is facilitated by pH (independent or dependent?) fusion protein

Answer 17

Independent

Question 18

Receptor mediated endocytosis for enveloped viruses, fusion protein requires (high or low?) pH to get activated and is thus pH (dependent or independent?).

Answer 18

Low pH

pH dependent

Question 19

What happens during virus uncoating?

Answer 19

1. Release of viral genome in host cell

2. Virion can no longer be detected

Question 20

Once uncoating is done, virions have a loss of __________

Answer 20

infectivity

Question 21

What two functions does the parent virus have?

Answer 21

1. Multiple copies for new viruses

2. Viral proteins for capsid and successful replication

Question 22

What is reverse transcriptase?

Answer 22

Used by retroviruses for conversion of viral RNA to cDNA during virus replication

Question 23

T/F: During processing of primary RNA transcript (pre-mRNA), the viral mRNA must conform to requirements of host cell translation system

Answer 23

True

Question 24

What are the 3 series of modifications, known as processing of primary RNA transcript (pre-mRNA)?

Answer 24

1. Capping
2. Addition of PolyA tail
3. Splicing

Question 25

After processing of primary RNA transcript (pre-mRNA), mRNA is translated in the _________

Answer 25

Cytoplasm

Question 26

Capping is the addition of 7-methylguanosine to the ____ end of RNA

Answer 26

5'

Question 27

Addition of poly-adenylated tail is at the ______ end of RNA

Answer 27

3'

Question 29

RNA splicing is a process that removes __________ and joins ____________ in a primary transcript

Answer 29

1. Introns | 2. Extrons

Question 30

What are two types of viral mRNA?

Answer 30

1. Monocistronic | 2. Polycistronic

Question 31

Monocistronic viral mRNA encode how many polypeptides?

Answer 31

One

Question 32

Polycistronic encode how many polypeptides?

Answer 32

Several

Question 33

T/F: Assembly and maturation of virus genome and proteins into new virions follow any order

Answer 33

False, follow a specific order

Question 34

Assembly and maturation may take place in what 3 cellular locations?

Answer 34

1. Nucleus 2. Cytoplasm 3. Plasma/cell membrane (most enveloped viruses

Question 35

How do naked virions release progeny virions?

Answer 35

Lysis of host cell

Question 36

How do enveloped virions release progeny virions?

Answer 36

Budding

Question 37

Why can't naked virions exit host cell via budding?

Answer 37

Lack envelope

Question 38

Viruses that acquire envelope while budding from ER, Golgi apparatus or nucleus membrane leave infected host cell by _______________

Answer 38

Exocytosis

Question 39

What are two ways retroviruses replicate?

Answer 39

1. Reverse transcriptase (RNA to DNA) | 2. Integrase (integrate viral DNA into host genome)

Question 40

What are the two ways viruses acquire lipid envelope?

Answer 40

1. Host cell | 2. Budding

Question 41

What are 3 ways of cell-to-cell spread of viruses?

Answer 41

1. Extracellular spread 2. Intracellular spread 3. Nuclear spread of virus genome

Question 42

What 3 things result from intracellular spread of viruses?

Answer 42

1. Rapid virus dissemination 2. Evasion of immune system 3. Persistent infections

Question 43

T/F: An exon codes for amino acids and an intron does not code for amino acids

Answer 43

True