Virus Replication Flashcards
T/F: Viruses have the genetic capability to multiply by division.
FALSE!
Viruses do NOT have the genetic capability to multiply by division.
A virus hijacks and utilizes the host cell machinery to produce what?
To produce its proteins and nucleic acid for the next generation of virus
What does the process of virus replication in a host cell resemble?
An assembly line
Permissive Cell
A cell in which a virus is able to replicate.
i.e. the machinery SUPPORTS REPLICATION of the virus
Non- Permissive Cell
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
_______ refers to the number of virions that are added per cell during infection.
MOI (Multiplicity of Infection)
What steps are included in the One-Step Virus Growth Curve?
1) Adsorption
2) Eclipse Period
3) Latent Period
4) Burst Size
During this period, the virus attaches to and enters the cells, and the titer of free virus in the medium may actually decline.
Adsorption
________ period: After uncoating and till just before 1st appearance of INTRACELLULAR new virus particle.
Eclipse Period
________ period: After uncoating and till just before 1st appearance of EXTRACELLULAR new virus particle.
Latent Period
The time before new infectious virus appears in the medium
Latent Period
During this phase no extracellular virions are detected.
Latent Period
Burst Size
The number of infectious virions released per average cell
The 6 Steps of Virus Replication in order
1) Attachment
2) Penetration
3) Uncoating
4) Synthesis of viral components (Nucleic acid and Protein)
5) Assembly and Maturation
6) Release in Large numbers
T/F: Virus attachement to a receptor(s) on host cell is not specific.
FALSE!!!
Virus attachment to a receptor(s) on host cell is VERY SPECIFIC (like a lock and key)
T/F: Each virus has its own specific receptor or receptors on specific host cells.
True
What is the attachment on host cell surface mediated by?
Interactions between the virus and complimentary receptor on the host cell surface.
T/F: Cells that lack the appropriate receptor escape being infected by the virus.
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)
T/F: In all cases, binding to a cell receptor is sufficient for infection.
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.
What is an example of a virus that may use more than one host cell receptor?
HIV
What are the different types of Penetration?
1) Endocytosis
2) Surface Fusion
3) Pore- Mediated Penetration
4) Antibody- Mediated Penetration
Penetration types of Noneveloped/ Naked Viruses
1) Receptor mediated endocytosis (Commonly Seen)
2) Pore mediated penetration (In some naked viruses)
Penetration types of Enveloped Viruses
1) Surface membrane fusion (have pH INDEPENDENT fusion protein)
2) Receptor mediated endocytosis (have pH DEPENDENT fusion protein)
What is an example of receptor mediated endocytosis that is commonly seen in nonenveloped/ naked viruses?
Cathrin- mediated endocytosis
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.
Pore- mediated endocytosis
Which penetration type of enveloped viruses have a pH INDEPENDENT fusion protein?
Surface membrane fusion
Which penetration type of enveloped viruses have a pH DEPENDENT fusion protein?
Receptor mediated endocytosis
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?
Surface membrane fusion
What is the name of the penetration for enveloped viruses in which fusion of virus membrane with host endosomal membrane release viral genome?
Receptor mediated endocytosis
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.
Receptor mediated endocytosis
FIPV uses an uncommon penetration method of entry, which method does it use?
Antibody- mediated attachment and penetration
What is the name of the step in virus replication where the viral genome is released in the host cell?
Uncoating
T/F: During uncoating the virion can no longer be detected, but the virion can still be infective.
FALSE!
During uncaring the virion can no longer be detected, and their is LOSS OF INFECTIVITY OF THE VIRIONS!
During synthesis of viral components ( nucleic acid and protein) what are the functions of the parent virus?
Function 1: Multiple copies for new viruses (children/ progeny)
Function2: Viral proteins for capsid and successful replication
Reverse Transcriptase converts viral ___A.___ to ___B.____ during virus replication
A. RNA
B. cDNA
T/F: Viral DNA must conform to the requirements of host cell translation system during the Processing of Primary RNA Transcript.
FALSE!
Viral mRNA!!! must conform to the requirements of host cell translation system.
A series of modifications occur, known as processing of primary RNA Transcript/ Pre-RNA. What are these series of modifications?
- Capping
- Addition of Poly A tail
- Splicing
T/F: During capping there is an addition of 7- methylguanosinn to the 5’ end of RNA
True
T/F: During the Addition of a Poly A tail there is a stretch of adenylate residues added to the 3’ end.
True
RNA splicing is a process that removes _____A.____ and joins ____B.____ in a primary transcript.
A. Introns
B. Exons
_______ is the portion of gene that codes for amino acids.
Exon
_______ is the portion of a gene that does NOT code for amino acids.
Intron
After processing, mRNAs are translated in the: A. Nucleus B. E.R. C. Cytoplasm D. Mitochondria
C. Cytoplasm
Viral mRNAs produced in the \_\_\_\_\_\_\_\_\_ must be exported to the cytoplasm. A. Nucleus B. Rough E.R. C. Smooth E.R. D. Mitochondria
A. Nucleus
What are the 2 types of Viral mRNA?
- Monocistronic
2. Polycistronic
Monocistronic is mRNA that encodes _____ polypeptides.
one
Polycistronic is mRNA that encodes ______ polypeptides.
Several
Where can assembly and maturation take place?
- Nucleus
- Cytoplasm
- Plasma/ Cell Membrane (Most Enveloped Viruses)
Assembly and maturation of MOST enveloped viruses takes place: A. Plasma/ Cell Membrane B. Nucleus C. Cytoplasm D. Mitochondria
A. Plasma/ Cell Membrane
T/F: Assembly of virus genome and proteins into new virions can occur in any order.
FALSE!!
Assembly of virus genome and proteins into new virions follows a SPECIFIC ORDER!
T/F: Naked Virions cause lysis of the host cell. They can then exit the host cell by budding because they lack an envelope.
FALSE!!
Naked Virions cause lysis of the host cell. They can NOT exit the host cell by budding because they lack an envelope.
Enveloped virions are released in large numbers, by exiting the host cell via _______.
Budding
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
C. Mitochondria membrane.
ER; Nuclear/ nucleus membrane and the Golgi apparatus
T/F: Viruses mature by budding through the membrane of the Golgi apparatus or ER during exocytosis.
True
Vesicles containing the virus migrate to the plasma membrane and are released by __________.
Exocytosis
Replication of retroviruses can occur via ____A.____ and ____B.______.
A. Reverse Transcriptase
B. Integrase
_________ synthesizes RNA into DNA.
Reverse Transcriptase
_________ integrates viral DNA into the host genome.
Integrase
How can viruses spread from cell to cell?
- Extracellular Spread
- Intercellular Spread
- Nuclear Spread of Virus Genome
This type of cell to cell spread results in rapid virus dissemination, evasion of immune system and persistent infections.
Intercellular Spread
