L4 Viral morphology and replication Flashcards
What is the common size for viruses? They have to be observed
0.02-0.03 uM (nanometer)
What is the difference between virion and virus?
Virion: extracellular state
Virus: intracellular state/ capsid removed
Which of the following are correct about viruses?
A. They are dependent on living cells for replication
B. They are non-motile
C. They are obligate intracellular
D. They are acellular
E. They have nucleus
F. They lack organelles for metabolism
G. They can redirect host cells as synthetic machinery
All except E
They do not have nucleus
Can virus have both DNA and RNA?
No, only DNA or RNA
List the differences between DNA and RNA viruses. (4)
- Strand
DNA: DS (double strand) more common
RNA: SS (single strand more common - Site of replication
DNA: in the nucleus
RNA: in cytoplasm - Transcription
DNA: must transcribe DNA > RNA
RNA: No need to transcribe to RNA - Stability
DNA: more stable: DNA polymerase has proof-reading
RNA: less stable: RNA polymerase and reverse transcriptase have no proof-reading
Functions of virus genome include integration and tumor formation. Briefly describe.
- Integration: dsDNA resembles human DNA and can be integrated into host DNA
- Tumor information: oncoprotein, e.g. HPV E6, E7 proteins (cut and ligate > when human DNA replicates > replicate too)
What is a caspid of a virus?
Protein coat formed by capsomeres (repearing protein subunits)
Which of the following are functions of caspid? A. Protect nucleic acid form degradation B. Receptor bidngin for naked virus C. Facilitate entry into host cell D. Marker for diagnosis E. Antigen to stimulate immune response F. Component of vaccine
All of the above
What are the differences of icosahedral and helical caspids? Give examples of each caspid too. (4)
Icosaheral: = cubic, spherical, DNA/RNA
e.g. Herpesvirus, HIV, Adenovirus, Papillomavirus
Helical: = rod like, RNA only
e.g. Influenza, rabies, Ebolavirus
Enveloped virus contains envelop enclosing the viral protein core. Why can they be killed by using disinfectants?
The envelop is acquired by budding through host plasma membrane, thus it is a lipid bilayer membrane with high lipid content
Which of the following about enveloped virus are correct?
A. They have viral specific surface glycoproteins as receptor-binding proteins
B. They are susceptible to heat
C. They are susceptible to detergents
D. They are targets of antivirals and vaccines
E. Naked virus are more resistant to heat and detergents
All of the ablve!
Nearly all gastroeneteritis virus like norovirus are naked virus (not enveloped), thus cannot be killed by alcohol.
How many layers of proteins are there in Rotavirus?
3
Name the targets for antiviral and vaccines in different types of viral proteins. (2) (naked and enveloped)
What are the targets of drugs in viral proteins? (1)
Naked virus: caspid proteins
Enveloped virus: surface glycoproteins
Enzymes are the target of drugs
What is ressortment in viral genome?
Virus with segmented genomes can exchange whole segment of genetic information creating novel features for the next generation.
DNA virus can be divided into enveloped and naked viruses. Give examples of each category of virus.
Enveloped: Herpes (HSV1), Hepadna (HBV)
Naked: Papillomavirus (e.g. HPV), Adenovirus
RNA viruses can be divided into double and single stranded viruses. Give the only example of virus that is double-stranded (naked too).
Reovirus (e.g. Rotavirus)
Single-stranded RNA virus can be further divided into positive and negative-stranded viruses.
Negative stranded, enveloped Orthomyoxiviridae and Paramyxoviridae are examples. Give an example for each of them.
Orthomyoxiviridae: Influenza
Paramyxoviridae: RSV, parainfluenza
Single-stranded, positive-stranded, enveloped RNA:
A. Flavivirus e.g. Dengue, Japanese encephalitis
B. Retrovirus e.g. HIV
C. Calicivirus e.g. Norovirus
A and B only
C: Should be Single-stranded, positive-stranded, NAKED RNA
Viral replication cycle:
A. (1)Attachment of virus to host cell receptors determines what ell can be infected
B. (2)All viruses penetrate the host cells by the same way
C. (3) Virus then release nucleic acid into the nucleus or cytoplasm of the host cell - uncoating
D. (4) Only mRNA are formed furing macromolecular synthesis
A and C
only
B: by 3 different ways
D: Early mRNA and protein synthesis: proteins are also formed
- Proteins to shut off host cell
- Proteins to replicate viral genome if needed
> Replication of the viral genome
Late mRNA and protein synthesis: structural proteins are formed
At the stage of macromolecular synthesis in viral replication cycle, what happens in during the replication of genome?
Replication of the viral genome +/- integrate into host DNA +/- transcription for viral mRNA > translation of mRNA in the cytoplasm
After macromolecular synthesis, there is postranslational modification of proteins, then the assembly of new virus particles to caspid. What happens in this stage?
Encapsulation of nucleic acid > insertion of envelop proteins into plasma membrane
The release of newly formed virus are different in naked and enveloped virions, briefly describe.
Naked virions: By lysis of host cells > no persistent productive infections
Enveloped virus: By budding, cell senescence, but may produce a low level of virus for years e.g. in chronic HepB
In retrovirus replication cycle e.g. HIV, (it is an enveloped ssRNA virus), what are involved?
A. Reverse transcriptase
B. Protesase
C. Integrase
All of the above
