Virus Replication

Question 1

T/F: Viruses have the genetic capability to multiply by division.

Answer 1

FALSE!

Viruses do NOT have the genetic capability to multiply by division.

Question 2

A virus hijacks and utilizes the host cell machinery to produce what?

Answer 2

To produce its proteins and nucleic acid for the next generation of virus

Question 3

What does the process of virus replication in a host cell resemble?

Answer 3

An assembly line

Question 4

Permissive Cell

Answer 4

A cell in which a virus is able to replicate.

i.e. the machinery SUPPORTS REPLICATION of the virus

Question 5

Non- Permissive Cell

Answer 5

Cell in which a factor or factors necessary to viral reproduction is not present or one detrimental to viral reproduction is present.
i.e. ABSENCE OF APPROPRIATE RECEPTORS

Question 6

_______ refers to the number of virions that are added per cell during infection.

Answer 6

MOI (Multiplicity of Infection)

Question 7

What steps are included in the One-Step Virus Growth Curve?

Answer 7

1) Adsorption
2) Eclipse Period
3) Latent Period
4) Burst Size

Question 8

During this period, the virus attaches to and enters the cells, and the titer of free virus in the medium may actually decline.

Answer 8

Adsorption

Question 9

________ period: After uncoating and till just before 1st appearance of INTRACELLULAR new virus particle.

Answer 9

Eclipse Period

Question 10

________ period: After uncoating and till just before 1st appearance of EXTRACELLULAR new virus particle.

Answer 10

Latent Period

Question 11

The time before new infectious virus appears in the medium

Answer 11

Latent Period

Question 12

During this phase no extracellular virions are detected.

Answer 12

Latent Period

Question 13

Burst Size

Answer 13

The number of infectious virions released per average cell

Question 14

The 6 Steps of Virus Replication in order

Answer 14

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 15

T/F: Virus attachement to a receptor(s) on host cell is not specific.

Answer 15

FALSE!!!

Virus attachment to a receptor(s) on host cell is VERY SPECIFIC (like a lock and key)

Question 16

T/F: Each virus has its own specific receptor or receptors on specific host cells.

Answer 16

True

Question 17

What is the attachment on host cell surface mediated by?

Answer 17

Interactions between the virus and complimentary receptor on the host cell surface.

Question 18

T/F: Cells that lack the appropriate receptor escape being infected by the virus.

Answer 18

True
(note: if the host cell does not have the specific receptor for the virus, the virus will not be able to attach to the host cell; therefore the host cell escapes being infected by the virus)

Question 19

T/F: In all cases, binding to a cell receptor is sufficient for infection.

Answer 19

FASLE!!!
In SOME cases, binding to a cell receptor is NOT sufficient for infection. – in some cases an additional cell surface molecule, or CO-RECEPTOR, is required for entry.

Question 20

What is an example of a virus that may use more than one host cell receptor?

Answer 20

HIV

Question 21

What are the different types of Penetration?

Answer 21

1) Endocytosis
2) Surface Fusion
3) Pore- Mediated Penetration
4) Antibody- Mediated Penetration

Question 22

Penetration types of Noneveloped/ Naked Viruses

Answer 22

1) Receptor mediated endocytosis (Commonly Seen)

2) Pore mediated penetration (In some naked viruses)

Question 23

Penetration types of Enveloped Viruses

Answer 23

1) Surface membrane fusion (have pH INDEPENDENT fusion protein)
2) Receptor mediated endocytosis (have pH DEPENDENT fusion protein)

Question 24

What is an example of receptor mediated endocytosis that is commonly seen in nonenveloped/ naked viruses?

Answer 24

Cathrin- mediated endocytosis

Question 25

What is the name of the penetration type when some non-enveloped viruses inject their genome into the host cytoplasm through creation of a pore in the host membrane.

Answer 25

Pore- mediated endocytosis

Question 26

Which penetration type of enveloped viruses have a pH INDEPENDENT fusion protein?

Answer 26

Surface membrane fusion

Question 27

Which penetration type of enveloped viruses have a pH DEPENDENT fusion protein?

Answer 27

Receptor mediated endocytosis

Question 28

What is the name of the penetration for enveloped viruses in which fusion of virus envelope with host cell membrane occurs directly on the surface of the host cell?

Answer 28

Surface membrane fusion

Question 29

What is the name of the penetration for enveloped viruses in which fusion of virus membrane with host endosomal membrane release viral genome?

Answer 29

Receptor mediated endocytosis

Question 30

In this method of penetration for enveloped viruses, the fusion proteins require low pH to get activated, which is achieved in endosome and thus facilitate virus envelope fusion with endosomal membrane.

Answer 30

Receptor mediated endocytosis

Question 31

FIPV uses an uncommon penetration method of entry, which method does it use?

Answer 31

Antibody- mediated attachment and penetration

Question 32

What is the name of the step in virus replication where the viral genome is released in the host cell?

Answer 32

Uncoating

Question 33

T/F: During uncoating the virion can no longer be detected, but the virion can still be infective.

Answer 33

FALSE! | During uncaring the virion can no longer be detected, and their is LOSS OF INFECTIVITY OF THE VIRIONS!

Question 34

During synthesis of viral components ( nucleic acid and protein) what are the functions of the parent virus?

Answer 34

Function 1: Multiple copies for new viruses (children/ progeny) Function2: Viral proteins for capsid and successful replication

Question 35

Reverse Transcriptase converts viral ___A.___ to ___B.____ during virus replication

Answer 35

A. RNA | B. cDNA

Question 36

T/F: Viral DNA must conform to the requirements of host cell translation system during the Processing of Primary RNA Transcript.

Answer 36

FALSE! | Viral mRNA!!! must conform to the requirements of host cell translation system.

Question 37

A series of modifications occur, known as processing of primary RNA Transcript/ Pre-RNA. What are these series of modifications?

Answer 37

1. Capping 2. Addition of Poly A tail 3. Splicing

Question 38

T/F: During capping there is an addition of 7- methylguanosinn to the 5' end of RNA

Answer 38

True

Question 39

T/F: During the Addition of a Poly A tail there is a stretch of adenylate residues added to the 3' end.

Answer 39

True

Question 40

RNA splicing is a process that removes _____A.____ and joins ____B.____ in a primary transcript.

Answer 40

A. Introns | B. Exons

Question 41

_______ is the portion of gene that codes for amino acids.

Answer 41

Exon

Question 42

_______ is the portion of a gene that does NOT code for amino acids.

Answer 42

Intron

Question 43

``` After processing, mRNAs are translated in the: A. Nucleus B. E.R. C. Cytoplasm D. Mitochondria ```

Answer 43

C. Cytoplasm

Question 44

``` Viral mRNAs produced in the _________ must be exported to the cytoplasm. A. Nucleus B. Rough E.R. C. Smooth E.R. D. Mitochondria ```

Answer 44

A. Nucleus

Question 45

What are the 2 types of Viral mRNA?

Answer 45

1. Monocistronic | 2. Polycistronic

Question 46

Monocistronic is mRNA that encodes _____ polypeptides.

Answer 46

one

Question 47

Polycistronic is mRNA that encodes ______ polypeptides.

Answer 47

Several

Question 48

Where can assembly and maturation take place?

Answer 48

1. Nucleus 2. Cytoplasm 3. Plasma/ Cell Membrane (Most Enveloped Viruses)

Question 49

``` Assembly and maturation of MOST enveloped viruses takes place: A. Plasma/ Cell Membrane B. Nucleus C. Cytoplasm D. Mitochondria ```

Answer 49

A. Plasma/ Cell Membrane

Question 50

T/F: Assembly of virus genome and proteins into new virions can occur in any order.

Answer 50

FALSE!! | Assembly of virus genome and proteins into new virions follows a SPECIFIC ORDER!

Question 51

T/F: Naked Virions cause lysis of the host cell. They can then exit the host cell by budding because they lack an envelope.

Answer 51

FALSE!! | Naked Virions cause lysis of the host cell. They can NOT exit the host cell by budding because they lack an envelope.

Question 52

Enveloped virions are released in large numbers, by exiting the host cell via _______.

Answer 52

Budding

Question 53

``` Viruses acquire their envelope by budding from all of the following when leaving the host cell by exocytosis, EXCEPT: A. ER B. Nuclear/ nucleus membrane C. Mitochondria membrane D. Golgi apparatus ```

Answer 53

C. Mitochondria membrane. ER; Nuclear/ nucleus membrane and the Golgi apparatus

Question 54

T/F: Viruses mature by budding through the membrane of the Golgi apparatus or ER during exocytosis.

Answer 54

True

Question 55

Vesicles containing the virus migrate to the plasma membrane and are released by __________.

Answer 55

Exocytosis

Question 56

Replication of retroviruses can occur via ____A.____ and ____B.______.

Answer 56

A. Reverse Transcriptase | B. Integrase

Question 57

_________ synthesizes RNA into DNA.

Answer 57

Reverse Transcriptase

Question 58

_________ integrates viral DNA into the host genome.

Answer 58

Integrase

Question 59

How can viruses spread from cell to cell?

Answer 59

1. Extracellular Spread 2. Intercellular Spread 3. Nuclear Spread of Virus Genome

Question 60

This type of cell to cell spread results in rapid virus dissemination, evasion of immune system and persistent infections.

Answer 60

Intercellular Spread