102 Questions
What is the main function of viral capsids?
To protect nucleic acids from physical and enzymatic damages
What is the pericapsid and which families of viruses have it?
It is composed of phospholipids and is present only in some families of viruses like orthomyxovirus and herpesvirus
What is the role of capsid proteins of naked viruses?
To mediate the binding and penetration of virus inside the host cell
What is the function of RNA-dependent RNA polymerase in viral replication?
To synthesize mRNAs for translation
What is the role of retroviral reverse transcriptase in viral replication?
To synthesize DNA from an RNA template
Which type of RNA is used for the synthesis of new molecules of viral genome in riboviruses with double-stranded RNA?
(-) RNA strand
What is the function of integrase in retroviral replication?
To catalyze the integration of viral DNA into host genome
What is the only function of the genomic RNA in riboviruses with diploid genome?
To be used for the synthesis of double-stranded DNA
What is the role of pericapsid in viral sensitivity to organic disinfectants?
Pericapsid dissolves lipids in the virus
What is the difference between productive and abortive viral infection?
Productive infection leads to the production of viral particles, while abortive infection does not
What is viral tropism?
The ability of the virus to recognize specific receptors and infect specific cell types
What is the period between viral penetration and maturation called?
Period of eclipse
What is the function of M2 protein in influenza virus?
Acts as an ion channel and causes acidification of endocytic vesicle containing the virus
What is the replication strategy of Picornaviridae and Flaviviridae?
Their complete linear RNA genomes act as mRNA and is translated into a viral polyprotein which is subsequently cleaved into individual proteins by the viral protease.
What is the function of RNA polymerase in + RNA viruses?
Synthesis of viral genome and mRNAs for structural proteins.
Which virus group has only the translation of the 5' portion of viral genome?
Togaviruses, coronaviruses and caliciviruses (hepatitis E virus).
What is the difference between the replication strategy of Parvovirus and Papovavirus?
Parvovirus can replicate only in cells that are in active proliferation, while Papovaviruses induce the progression of the cell cycle from the G1 to the S phase.
What is the function of (-) RNA in riboviruses with negative RNA genome?
It cannot serve as mRNA.
What is the replicative strategy for DNA viruses in the 1st group?
Viral gene expression occurs in the nucleus through RNA polymerase II
What is the replicative strategy for DNA viruses in the 2nd group?
The entire replication cycle is completed in the cytoplasm
What is the replicative strategy for DNA viruses in the 3rd group?
Viral gene expression requires synthesis of a complementary DNA strand
What is the replicative strategy for DNA viruses in the 4th group?
Viral gene expression occurs in the nucleus through RNA polymerase II
What do DNA viruses require to replicate their genome?
Their own DNA polymerase encoded in their genome
What is the function of capsid proteins in naked viruses?
To mediate the binding and penetration of the virus inside the host cell
What is the function of pericapsid in some families of viruses?
To act as virus receptor to target cells
What is the role of nucleases and esterase in viral infections?
To cause enzymatic damages to nucleic acids
What is the main function of viral capsids?
To protect nucleic acids from physical damages and enzymatic damages
Which viral component is often the major antigen of naked viruses?
Capsid proteins
What is the replicative strategy for DNA viruses in the 2nd group?
They complete the replication cycle in the cytoplasm
What is the replicative strategy for DNA viruses in the 3rd group?
Their genome encodes for a DNA polymerase
Which enzyme is used by HBV to synthesize its genome?
Reverse transcriptase
How many replicative strategies do DNA viruses in the 1st group follow for the synthesis of mRNAs?
3
Which virus group has a partially double-stranded DNA genome?
Hepadnaviruses
What is the function of RNA-dependent RNA polymerase in viral replication?
To synthesize new molecules of viral genome from template RNAs
Which type of RNA is used for the synthesis of new molecules of viral genome in retroviruses?
Genomic RNA
What is the function of integrase in retroviral replication?
To integrate viral DNA into host genome
What is the only function of the genomic RNA in riboviruses with diploid genome?
To be used for the double-stranded DNA synthesis
What is the role of (+) RNA in retroviruses?
To serve as mRNAs for translation
What is the period between viral penetration and maturation of viral progeny called?
Period of eclipse
What is the function of M2 protein in influenza virus?
It acts as an ion channel and causes the acidification of endocytic vesicle containing the virus
What is viral tropism?
The ability of the virus to recognize specific receptors and thus to infect specific cell types
What is the role of pericapsid in viral sensitivity to organic disinfectants?
It accounts for the sensitivity of certain viruses to organic disinfectants
What is the difference between productive and abortive viral infection?
Productive infection leads to the production of viral particles, while abortive infection does not
What is the replicative strategy for riboviruses with negative RNA genome?
They synthesize new molecules of RNA with negative polarity
Which virus group has complete linear RNA genomes that act as mRNA?
Picornaviridae and Flaviviridae
What is the function of RNA-dependent RNA polymerase in + RNA viruses?
It synthesizes new molecules of RNA with positive polarity
Which cells can Parvovirus replicate in?
Cells that are in active proliferation
Which viruses have only the translation of the 5' portion of viral genome?
Togaviruses, Coronaviruses and Caliciviruses
What is the main function of viral capsids?
To protect nucleic acids from physical and enzymatic damages
What is the function of pericapsid in some families of viruses?
It is composed of phospholipids derived from cytoplasmic or intracellular membranes
What is the role of capsid proteins of naked viruses?
To mediate the binding and penetration of the virus inside the host cell
What can cause mutations in nucleic acids?
UV radiation
What is the composition of pericapsid in some families of viruses?
Viral glycoproteins and phospholipids
What is the period between viral penetration and maturation of viral progeny called?
Period of eclipse
What is the function of M2 protein in influenza virus?
It acts as an ion channel and causes the acidification of endocytic vesicle containing the virus
What is viral tropism?
The ability of the virus to recognize specific receptors and infect specific cell types
What is the role of pericapsid in viral sensitivity to organic disinfectants?
It accounts for the sensitivity of certain viruses to organic disinfectants that can dissolve lipids
What is the difference between productive and abortive viral infection?
Productive infection leads to the production of viral particles while abortive infection does not result in the production of viral particles
What is the replicative strategy for DNA viruses in the 2nd group?
The entire replication cycle is completed in the cytoplasm
Which group of DNA viruses requires the completion of the + strand by cellular enzymes before viral gene expression?
4th group
What is the difference in the number of phases of viral gene expression between Herpesviruses/Adenoviruses and Papovaviruses?
Herpesviruses/Adenoviruses have 3 phases, Papovaviruses have 2 phases
Which group of DNA viruses requires synthesis of the complementary DNA strand before gene expression by the cellular RNA polymerase II?
3rd group
Which DNA virus group uses a RNA-dependent DNA polymerase to synthesize its genome?
4th group
What type of cells can Parvovirus replicate in?
Cells in active proliferation
Which group of viruses includes Picornaviridae and Flaviviridae?
Viruses with (+) sense RNA genomes
What is the function of RNA-dependent RNA polymerase in (+) RNA viruses?
Synthesis of new molecules of RNA with positive polarity for viral genome and mRNAs
Which type of RNA cannot serve as mRNA in riboviruses?
Single-stranded RNA with negative polarity
What is the difference between the replication strategy of Parvovirus and Papovavirus?
Parvovirus induces the progression of the cell cycle from the G1 to the S phase, while Papovavirus can replicate only in cells that are in active proliferation
What is the role of RNA-dependent RNA polymerase in viral replication?
It synthesizes both (+) and (-) RNA strands in riboviruses with double-stranded RNA
Which enzyme is responsible for the synthesis of DNA from an RNA template in retroviruses?
Reverse transcriptase
What is the only function of the genomic RNA in riboviruses with diploid genome?
To be used for the double stranded DNA synthesis
What is the function of retroviral integrase?
It catalyzes the integration of viral DNA into the host genome
Which viruses have a segmented double-stranded RNA?
Reoviruses and Rotaviruses
What is the concept of quasi-species in viral populations?
The presence of genetically different viral variants in the same infected individual
What is the most error-prone viral replicative enzyme?
Reverse transcriptase of HBV and retroviruses
What can cause a genetic change to be stabilized in viral populations?
Both random fluctuations and selective advantage
What are the ways in which viruses can be genetically modified?
Both acquiring mutations and re-assortment/recombination
What is the most variable region of the HIV genome?
Env gene
Which HIV-1 mutations make the virus resistant to almost all NNRTIs?
Y181C and Y181I
Which virus has the smallest known animal DNA genome?
HBV
Which group of drugs target almost every step of HIV replication?
Nucleos(t)ide reverse transcriptase inhibitors
Which virus uses Reverse Transcriptase for its genome replication?
HBV
What is the most frequent genotype of Hepatitis C Virus worldwide and in Europe?
Genotype 1
Which genotype of Hepatitis C Virus is significantly more prevalent among patients with liver cirrhosis and those with decompensated liver disease requiring liver transplantation?
Genotype 1
What is the most efficient genotype of Hepatitis C Virus in driving steatosis?
Genotype 3
What is the most important baseline predictor for response to Peg-IFN + Ribavirin Combination Therapy in Hepatitis C Virus?
Genotype
What is the error rate of RT enzyme during transcription of HIV genome?
1:2,000-10,000 bases
What is antigenic drift?
A gradual and continuous change in antigenic properties of a virus
Which viruses are subject to antigenic drift?
RNA viruses
What is antigenic shift?
A genetic reassortment that leads to new antigenic properties
Which virus is a classic example of a virus subjected to antigenic drift?
Influenza virus
Why is influenza virus prone to antigenic shift?
Because of its segmented genome
What is the practical implication of viral evolution?
It can explain seasonal outbreaks, host change and pandemics
How does genetic variability in S gene affect HBV oncogenic potential?
Deletions and stop codons can induce oxidative stress and favor neoplastic transformation of hepatocytes
What is the implication of deletions in pre-S regions in HBV?
It correlates with increased risk of liver cancer
What is the implication of viral variability in the efficacy of immunity?
It regulates the efficacy of natural and artificial immunity
What is the implication of viral variability in the development of a vaccine?
It can be relatively easy in some cases, and very difficult (nearly impossible) in others
What is viral recombination?
The exchange of homologous stretches of genetic material between two virus strains co-infecting the same cell
What is the reason for HCV's high degree of genetic variability?
It lacks a proofreading function in its polymerase
How do RNA viruses undergo recombination during replication?
By breaking and rejoining homologous nucleic acid strands already synthesized
What is the concept of quasispecies?
The high degree of variability of a virus at the patient level
What is the difference in recombination frequency between retroviruses and other viruses?
Retroviruses have a higher frequency of recombination
"Unraveling DNA Virus Replication Strategies: Can You Decode the Science?" Test your knowledge on the complex replicative strategies of DNA viruses, including herpesviruses, adenoviruses, and papovaviruses. Learn about the process of mRNA synthesis and the role of RNA polymerase II in viral gene expression. Challenge yourself with this quiz and enhance your understanding of DNA virus replication mechanisms.
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