Viral Evolution and Genetic Modification Quiz
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Questions and Answers

What is the function of RNA-dependent RNA polymerase in viral replication?

  • It integrates DNA into the host genome
  • It produces new molecules of viral genome
  • It synthesizes mRNAs that will be used for translation (correct)
  • It synthesizes DNA molecules from an RNA template

    • Which of the following riboviruses have a segmented double-stranded RNA?

  • Influenza viruses
  • Reoviruses and Rotaviruses (correct)
  • Coronaviruses
  • HIV

    • How do retroviruses replicate?

  • By synthesizing mRNAs for translation
  • By integrating DNA into the host genome
  • By synthesizing new molecules of viral genome from (+) RNAs
  • By using reverse transcriptase to synthesize DNA from an RNA template (correct)

    • What is the concept of quasi-species in viral genetics?

    <p>The presence of a swarm of genetically different viral variants in the same infected individual</p> Signup and view all the answers

    What is the main function of viral capsids?

    <p>To protect nucleic acids from physical and enzymatic damages</p> Signup and view all the answers

    What is the pericapsid composed of?

    <p>Phospholipids derived from cytoplasmic or intracellular membranes</p> Signup and view all the answers

    What is the function of capsid proteins in naked viruses?

    <p>To mediate the binding and penetration of the virus inside the host cell</p> Signup and view all the answers

    What are the enzymatic damages that nucleic acids are protected from by viral capsids?

    <p>Nucleases and esterase derived from dead cells or freely secreted as cellular defense against infections</p> Signup and view all the answers

    What is the replication strategy of viruses with a (+) sense RNA genome?

    <p>Their RNA genome acts as mRNA and is translated into a viral polyprotein</p> Signup and view all the answers

    Which type of cells can Parvovirus replicate in?

    <p>Progenitors of red blood cells</p> Signup and view all the answers

    What is the role of RNA polymerase in the replication of (+) sense RNA viruses?

    <p>To synthesize new molecules of RNA with positive polarity</p> Signup and view all the answers

    What is the replication strategy of viruses with a (-) sense RNA genome?

    <p>They cannot serve as mRNA</p> Signup and view all the answers

    What is the main reason for the high degree of genetic variability in HCV?

    <p>The virus has a high daily rate of viral production</p> Signup and view all the answers

    Which HCV genotype is the most frequent worldwide and in Europe?

    <p>Genotype 1</p> Signup and view all the answers

    What is the significance of HCV genotype 1b?

    <p>It is significantly more prevalent among patients with liver cirrhosis and those with decompensated liver disease requiring liver transplantation</p> Signup and view all the answers

    What is the error rate of RT enzyme during transcription of HIV genome?

    <p>1:2,000-10,000</p> Signup and view all the answers

    What is the estimated percentage of HIV isolates that represent recombinants between different subtypes?

    <p>Around 20%</p> Signup and view all the answers

    Which HIV gene is the most prone to variation?

    <p>Env gene</p> Signup and view all the answers

    What is the unique replication strategy used by HBV?

    <p>Reverse transcriptase</p> Signup and view all the answers

    What is the rate of mutations introduced by the reverse transcriptase of HBV?

    <p>1 mutation / 105 nucleotide</p> Signup and view all the answers

    Which type of HIV inhibitors target the attachment step of HIV replication?

    <p>Attachment inhibitors</p> Signup and view all the answers

    What is antigenic drift?

    <p>A gradual and continuous antigenic variation</p> Signup and view all the answers

    What is the most error-prone viral replicative enzyme?

    <p>Reverse transcriptase of HBV and retroviruses</p> Signup and view all the answers

    What is antigenic shift?

    <p>A sudden change in antigenic properties following genetic reassortment</p> Signup and view all the answers

    Which viruses are subject to antigenic drift?

    <p>Influenza virus, HIV, HBV, and HCV</p> Signup and view all the answers

    What is the mutation rate of DNA viruses?

    <p>1 mutation every 108-1011 base-pair per replication cycle</p> Signup and view all the answers

    What is the period between the penetration of virus into cells and the maturation of viral progeny called?

    <p>Period of eclipse</p> Signup and view all the answers

    What is viral tropism?

    <p>Ability of the virus to recognize specific receptors and infect specific cell types</p> Signup and view all the answers

    What is the enzyme associated with RNA viruses with a negative polarity (-)?

    <p>RNA-dependent RNA polymerase</p> Signup and view all the answers

    What is the role of M2 protein in influenza virus?

    <p>Acts as an ion channel and causes the acidification of endocytic vesicle containing the virus</p> Signup and view all the answers

    What is the difference between productive and abortive infection?

    <p>Productive infection leads to the production of viral particles, while abortive infection does not</p> Signup and view all the answers

    What is the most common route of dissemination for viruses?

    <p>Systemic blood (viremia)</p> Signup and view all the answers

    Which route of transmission is influenced by social and economic conditions?

    <p>Respiratory route</p> Signup and view all the answers

    What is a key factor for the establishment of infection after successful entry of the virus?

    <p>Availability of sensitive and permissive cells</p> Signup and view all the answers

    Which type of transmission interests adults only?

    <p>Genital route</p> Signup and view all the answers

    What is the mechanism by which viruses can migrate to find cells permissive for viral replication?

    <p>Systemic blood (viremia)</p> Signup and view all the answers

    What is the incubation period?

    <p>The interval between the acquisition of infection and the onset of disease.</p> Signup and view all the answers

    What is viral elimination?

    <p>The process of the virus leaving the body through the airway, digestive tract, or urogenital tract.</p> Signup and view all the answers

    What is distant spread in viral infections?

    <p>The spread of infection through the bloodstream.</p> Signup and view all the answers

    What is a latent infection?

    <p>An infection in which the virus remains in the host cell genome or cell nucleus.</p> Signup and view all the answers

    What is the purpose of the extensive overlapping of HBV open reading frames?

    <p>To optimize the genomic organization</p> Signup and view all the answers

    What is the effect of a mutation that has little effect on one viral protein but affects an overlapping gene?

    <p>It is not selected</p> Signup and view all the answers

    What is the consequence of the pattern of lamivudine resistance mutations M204V+L180M+V173L in RT?

    <p>It reduces the binding affinity with neutralizing antibodies</p> Signup and view all the answers

    What is the effect of deletions and stop codons in the S antigen?

    <p>It induces an oxidative stress favoring neoplastic transformation of hepatocytes</p> Signup and view all the answers

    What is the practical implication of viral evolution?

    <p>It regulates the efficacy of natural and artificial immunity</p> Signup and view all the answers

    What are the main routes of viral penetration into the host?

    <p>Respiratory, gastrointestinal, and genital routes</p> Signup and view all the answers

    What are some important events in the viral pathogenesis?

    <p>Viral replication, elimination of the virus by the host organism, and overcoming of local defenses</p> Signup and view all the answers

    What determines the virulence of a virus?

    <p>Small mutations in the genome</p> Signup and view all the answers

    What is the potential source of infection from blood transfusions?

    <p>Hepatitis B, hepatitis C, and HIV</p> Signup and view all the answers

    What is the most common route of viral penetration?

    <p>Respiratory route</p> Signup and view all the answers

    Which type of viruses are suspected to have some forms of latency?

    <p>Enteroviruses</p> Signup and view all the answers

    Which viruses are examples of chronic infections?

    <p>Hepatitis C virus</p> Signup and view all the answers

    What happens during a relapse of a virus?

    <p>The virus begins a new cycle of productive replication</p> Signup and view all the answers

    Which viruses have DNA replication intermediates?

    <p>Hepatitis B virus</p> Signup and view all the answers

    What is characteristic of chronic infections?

    <p>The virus is continuously present at lower levels</p> Signup and view all the answers

    What is the replicative strategy of Poxviruses?

    <p>Their entire replication cycle is completed in the cytoplasm</p> Signup and view all the answers

    Which DNA virus uses a RNA-dependent DNA polymerase to synthesize its genome?

    <p>Hepadnaviruses</p> Signup and view all the answers

    What is the main difference between the replicative strategies of Papovaviruses and Herpesviruses/Adenoviruses?

    <p>Papovaviruses replicate their genome in the cytoplasm, while Herpesviruses and Adenoviruses replicate their genome in the nucleus</p> Signup and view all the answers

    What is the replicative strategy of Parvoviruses?

    <p>They require two steps for gene expression</p> Signup and view all the answers

    What is the function of the reverse transcriptase enzyme in HBV replication?

    <p>To synthesize the viral genome</p> Signup and view all the answers

    What is the significance of antigenic shift in influenza viruses type A?

    <p>It can cause pandemic infections with completely different antigenic properties from the parental virus</p> Signup and view all the answers

    What is viral recombination?

    <p>Exchange of homologous stretches of genetic material between two virus strains co-infecting the same cell</p> Signup and view all the answers

    Which type of viruses have high frequency of recombination?

    <p>Retroviruses</p> Signup and view all the answers

    How does influenza virus undergo antigenic shift?

    <p>Due to the segmented nature of its genome</p> Signup and view all the answers

    What is the difference between genetic and non-genetic interactions in influenza virus?

    <p>Genetic interactions involve the interaction of virions' genomes while non-genetic interactions involve their end products</p> Signup and view all the answers

    What is the most common route of viral dissemination?

    <p>Systemic blood (viremia)</p> Signup and view all the answers

    Which route of transmission is influenced by social and economic conditions?

    <p>Transmission through the gastrointestinal tract</p> Signup and view all the answers

    Which type of transmission interests adults only?

    <p>Transmission through the genital route</p> Signup and view all the answers

    Which type of transmission is subject to environmental and seasonal influences?

    <p>Transmission through skin lesions caused by insects and animals</p> Signup and view all the answers

    What is the process by which a viral infection causes a disease called?

    <p>Pathogenesis</p> Signup and view all the answers

    What can a mutation in an overlapping gene of HBV potentially cause?

    <p>Severe consequences on an overlapping gene</p> Signup and view all the answers

    What is the consequence of deletions and stop codons in the S antigen of HBV?

    <p>Induction of oxidative stress</p> Signup and view all the answers

    What is the practical implication of viral evolution?

    <p>Regulating the efficacy of natural and artificial immunity</p> Signup and view all the answers

    What is the most effective way to control viruses with high propensity to variability?

    <p>Antiviral drug combinations</p> Signup and view all the answers

    What is the function of RNA-dependent RNA polymerase in viral replication?

    <p>To synthesize viral genome</p> Signup and view all the answers

    Which type of virus has a segmented double-stranded RNA?

    <p>Reoviruses and Rotaviruses</p> Signup and view all the answers

    What is the unique replication strategy used by retroviruses?

    <p>Using reverse transcriptase to synthesize DNA from RNA template</p> Signup and view all the answers

    What is the concept of quasi-species in viral genetics?

    <p>The presence of a swarm of genetically different viral variants in the same infected individual</p> Signup and view all the answers

    What is the genome size of HIV?

    <p>9749 nucleotides</p> Signup and view all the answers

    What is the replication enzyme used by HBV?

    <p>Reverse Transcriptase</p> Signup and view all the answers

    What is the estimated percentage of HIV isolates that represent recombinants between different subtypes?

    <blockquote> <p>20%</p> </blockquote> Signup and view all the answers

    Which HIV-1 mutations make the virus resistant to almost all NNRTIs?

    <p>Y181C and Y181I</p> Signup and view all the answers

    What is the replication rate of HBV RT?

    <p>1 mutation / 105 nucleotide</p> Signup and view all the answers

    What is the error rate of the reverse transcriptase enzyme during transcription of HIV genome?

    <p>1:2000</p> Signup and view all the answers

    What is the most prevalent HCV genotype in chronically infected patients worldwide and in Europe?

    <p>Genotype 1</p> Signup and view all the answers

    What is the concept of quasispecies in HCV?

    <p>A group of genetically diverse HCV viruses</p> Signup and view all the answers

    Which HCV genotype is significantly more prevalent among patients with liver cirrhosis and those with decompensated liver disease requiring liver transplantation?

    <p>Genotype 1b</p> Signup and view all the answers

    What is the effect of genotype 3 of HCV on intracellular lipid accumulation?

    <p>It is the most efficient in driving steatosis</p> Signup and view all the answers

    What is the double result of the spread of the virus and host survival?

    <p>Balance</p> Signup and view all the answers

    Which route of viral penetration is less common but still frequent?

    <p>Genital</p> Signup and view all the answers

    What are the important events in the viral pathogenesis?

    <p>Viral replication and overcoming of local defenses</p> Signup and view all the answers

    Which type of transmission occurs from mother to child through perinatal transfer or breast-feeding?

    <p>Maternal-fetal transmission</p> Signup and view all the answers

    What is a potential source of infection through blood products?

    <p>All of the above</p> Signup and view all the answers

    What is the replication strategy of viruses with a (+) sense RNA genome?

    <p>They use the cellular DNA polymerase to replicate in actively replicating cells</p> Signup and view all the answers

    What is the function of RNA dependent RNA polymerase in viral replication?

    <p>To synthesize new molecules of RNA with negative polarity</p> Signup and view all the answers

    Which type of cells can Parvovirus replicate in?

    <p>Only red blood cell progenitors</p> Signup and view all the answers

    What is the replication strategy of viruses with a (-) sense RNA genome?

    <p>They synthesize new molecules of RNA with positive polarity</p> Signup and view all the answers

    Which group of viruses includes the Picornaviridae and Flaviviridae?

    <p>Viruses with a (+) sense RNA genome</p> Signup and view all the answers

    What is the incubation period in viral infections?

    <p>The interval between acquisition of infection and the onset of disease</p> Signup and view all the answers

    Which of the following is a possible modality of viral elimination?

    <p>Airway</p> Signup and view all the answers

    What is distant spread in viral infections?

    <p>The spread of viruses to other parts of the body through the bloodstream or lymphatic system</p> Signup and view all the answers

    What is latent infection?

    <p>An infection that is no longer detectable as infectious virus</p> Signup and view all the answers

    Which route of viral dissemination involves the lymphatic drainage of virions and their release into the circulation?

    <p>Systemic infections</p> Signup and view all the answers

    What is a common characteristic of chronic viral infections?

    <p>The virus continues to be produced at high levels during the chronic phase.</p> Signup and view all the answers

    Which viruses are suspected to have some forms of latency?

    <p>Retroviruses and measles virus</p> Signup and view all the answers

    What is a relapse in a viral infection?

    <p>The virus wakes up and begins a new cycle of productive replication after a phase of latency.</p> Signup and view all the answers

    Which viruses have DNA replication intermediates?

    <p>Hepatitis B virus and papovaviruses</p> Signup and view all the answers

    What is the survival time of the host in chronic infections?

    <p>Long</p> Signup and view all the answers

    What is the main function of viral capsids?

    <p>To protect nucleic acids from physical and enzymatic damages</p> Signup and view all the answers

    What is the pericapsid composed of?

    <p>Phospholipids and viral glycoproteins</p> Signup and view all the answers

    What is the role of capsid proteins in naked viruses?

    <p>To mediate the binding and penetration of the virus inside the host cell</p> Signup and view all the answers

    What is the function of viral glycoproteins in the pericapsid?

    <p>To act as virus receptor to target cells</p> Signup and view all the answers

    What is the consequence of UV radiation on nucleic acids?

    <p>Chemical alteration causing mutations</p> Signup and view all the answers

    What is antigenic drift?

    <p>A gradual and continuous antigenic variation in a virus</p> Signup and view all the answers

    What is the most error-prone viral replicative enzyme?

    <p>Reverse transcriptase of HBV and retroviruses</p> Signup and view all the answers

    Which type of viruses are generally more genetically stable than RNA viruses?

    <p>DNA viruses</p> Signup and view all the answers

    What is antigenic shift?

    <p>The genetic reassortment of a virus resulting in extended changes in antigenic properties</p> Signup and view all the answers

    Which viruses are a classic example of viruses subjected to antigenic drift?

    <p>HCV and influenza virus</p> Signup and view all the answers

    What is viral tropism?

    <p>The ability of the virus to recognize specific receptors and infect specific cell types</p> Signup and view all the answers

    What is the period between the penetration of virus into cells and the maturation of viral progeny called?

    <p>Period of eclipse</p> Signup and view all the answers

    What is the difference between productive and abortive infection?

    <p>Productive infection leads to the production of viral particles, while abortive infection does not produce any viral particles</p> Signup and view all the answers

    What is the significance of the M2 protein in influenza virus?

    <p>It acts as an ion channel and causes the acidification of endocytic vesicle containing the virus</p> Signup and view all the answers

    What is the difference between acute and persistent viral infections?

    <p>Acute infections are extinguished with the healing and the disappearance of the virus from the body, while persistent infections may become latent, chronic, or slow infections</p> Signup and view all the answers

    What is antigenic shift in influenza viruses type A?

    <p>The generation of progeny with replication properties compatible with the human species and antigenic properties completely different from the parental human virus</p> Signup and view all the answers

    What is viral recombination?

    <p>The exchange of homologous stretches of genetic material between two virus strains co-infecting the same cell</p> Signup and view all the answers

    What is the difference between viral recombination and viral recombination between virus and host cell?

    <p>Viral recombination involves the exchange of homologous genetic material between two virus strains, while viral recombination between virus and host cell involves the acquisition of cellular genes by viral genomes</p> Signup and view all the answers

    What is the replication strategy of retroviruses?

    <p>The acquisition of cellular genes by viral genomes</p> Signup and view all the answers

    What is the frequency of recombination in viruses?

    <p>It is high in those viruses in which the exchange of the template strand is a normal event in the process of synthesis of the viral genome</p> Signup and view all the answers

    What is the main function of viral capsids?

    <p>To protect nucleic acids</p> Signup and view all the answers

    What is the pericapsid composed of?

    <p>Phospholipids and viral glycoproteins</p> Signup and view all the answers

    What is the role of capsid proteins in naked viruses?

    <p>To mediate the binding and penetration of the virus inside the host cell</p> Signup and view all the answers

    What is the significance of viral glycoproteins in the pericapsid?

    <p>To act as virus receptors to target cells</p> Signup and view all the answers

    What is the major antigen of naked viruses?

    <p>Capsid proteins</p> Signup and view all the answers

    What is the most common route of dissemination for viruses?

    <p>Systemic blood (viremia)</p> Signup and view all the answers

    Which route of transmission is poorly influenced by social and economic conditions?

    <p>Respiratory route</p> Signup and view all the answers

    Which type of transmission is influenced by social and economic conditions?

    <p>Gastrointestinal tract</p> Signup and view all the answers

    Which individuals are at risk for transmission through medical or surgical instruments, blood transfusions and blood products, and organ transplantation?

    <p>Professionals, politransfused, drug addicts</p> Signup and view all the answers

    Which route of transmission is less common, but frequently interests adults?

    <p>Genital route</p> Signup and view all the answers

    What is antigenic drift?

    <p>A gradual and continuous antigenic variation</p> Signup and view all the answers

    Which type of viruses have a relatively low mutation rate?

    <p>DNA viruses</p> Signup and view all the answers

    What is the most error-prone viral replicative enzyme?

    <p>Reverse transcriptase</p> Signup and view all the answers

    Which viruses are subject to antigenic drift?

    <p>Influenza virus, HIV, HBV, and HCV</p> Signup and view all the answers

    What is antigenic shift?

    <p>A sudden change in antigenic properties following a genetic reassortment</p> Signup and view all the answers

    What is the most frequent genotype of Hepatitis C Virus worldwide and in Europe?

    <p>Genotype 1</p> Signup and view all the answers

    What is the most efficient genotype in driving steatosis?

    <p>Genotype 3</p> Signup and view all the answers

    Which HCV genotype is significantly more prevalent among patients with liver cirrhosis and those with decompensated liver disease requiring liver transplantation?

    <p>Genotype 1b</p> Signup and view all the answers

    What is the most important baseline predictor for response to Peg-IFN + Ribavirin Combination Therapy in HCV?

    <p>HCV genotype</p> Signup and view all the answers

    What is the error rate of RT enzyme during transcription of HIV genome?

    <p>1:10,000</p> Signup and view all the answers

    What is the function of RNA-dependent RNA polymerase in viral replication?

    <p>It synthesizes viral genome from the viral RNA template</p> Signup and view all the answers

    Which type of RNA viruses have a segmented double-stranded RNA?

    <p>Reoviruses and Rotaviruses</p> Signup and view all the answers

    What is the enzyme responsible for the synthesis of DNA from an RNA template in retroviruses?

    <p>Reverse transcriptase</p> Signup and view all the answers

    What is the term used to indicate the presence of genetically different viral variants in the same infected individual?

    <p>Viral quasispecies</p> Signup and view all the answers

    What is the function of integrase in retroviruses?

    <p>It catalyzes the integration of viral DNA into the host genome</p> Signup and view all the answers

    What is the replicative strategy for poxviruses?

    <p>Poxviruses complete their entire replication cycle in the cytoplasm using a DNA-dependent RNA polymerase encoded by the viral genome.</p> Signup and view all the answers

    What is the replicative strategy for parvoviruses?

    <p>Parvoviruses have a single-stranded DNA genome and require two steps for gene expression.</p> Signup and view all the answers

    What is the replicative strategy for HBV?

    <p>HBV uses a RNA-dependent DNA polymerase to synthesize its genome.</p> Signup and view all the answers

    What are the important events in viral pathogenesis?

    <p>Viral replication and dissemination</p> Signup and view all the answers

    Which route of viral penetration is very common?

    <p>Gastrointestinal route</p> Signup and view all the answers

    What determines virulence for each type of virus?

    <p>The virus's pathogenic activity and host permissiveness</p> Signup and view all the answers

    Which type of transmission can occur through breast-feeding?

    <p>Maternal-fetal transmission</p> Signup and view all the answers

    Which type of viruses are examples of chronic infections?

    <p>RNA viruses</p> Signup and view all the answers

    What is the purpose of the unique genome organization of HBV?

    <p>To optimize the viral replication cycle</p> Signup and view all the answers

    What is the consequence of deletions and stop codons in the S antigen of HBV?

    <p>Inducing oxidative stress and promoting neoplastic transformation of hepatocytes</p> Signup and view all the answers

    What is the practical implication of viral evolution?

    <p>It can explain seasonal outbreaks, host change, and pandemics</p> Signup and view all the answers

    What is the characteristic of viruses with high propensity to variability?

    <p>They require drug combinations to be controlled</p> Signup and view all the answers

    What is the role of lamivudine resistance mutations in HBV?

    <p>They have little effect on the viral proteins</p> Signup and view all the answers

    What is the period between the penetration of virus into cells and the maturation of viral progeny called?

    <p>Period of eclipse</p> Signup and view all the answers

    What is the function of M2 protein in influenza virus?

    <p>It acts as an ion channel and causes the acidification of endocytic vesicle containing the virus</p> Signup and view all the answers

    What is viral tropism?

    <p>The ability of the virus to recognize specific receptors and infect specific cell types</p> Signup and view all the answers

    What is the consequence of deletions and stop codons in the S antigen of HBV?

    <p>It results in the production of truncated and non-functional S antigens</p> Signup and view all the answers

    What is the difference between productive and abortive viral infections?

    <p>Productive infection leads to the production of viral particles, while abortive infection does not</p> Signup and view all the answers

    What is the main difference between a relapse and a chronic infection?

    <p>A chronic infection is characterized by the continuous presence of the virus, while a relapse is a new cycle of productive replication.</p> Signup and view all the answers

    Which of the following viruses is suspected to have some forms of latency?

    <p>Measles virus</p> Signup and view all the answers

    Which viruses are examples of chronic infections?

    <p>Hepatitis B and C</p> Signup and view all the answers

    Which viruses can have forms of latency?

    <p>Only some RNA viruses</p> Signup and view all the answers

    What is the main characteristic of chronic infections?

    <p>The continuous presence of the virus, usually at lower levels, even after the acute phase</p> Signup and view all the answers

    What is the replicative strategy for DNA viruses with a partially double-stranded genome?

    <p>Completion of the genome by cellular enzymes followed by gene expression by RNA polymerase II</p> Signup and view all the answers

    What is the replicative strategy for Poxviruses?

    <p>Viral gene expression in the cytoplasm by a DNA-dependent RNA polymerase encoded by the viral genome</p> Signup and view all the answers

    What is the replicative strategy for Parvoviruses?

    <p>Viral gene expression in the cytoplasm by a DNA-dependent RNA polymerase encoded by the viral genome</p> Signup and view all the answers

    How many replicative strategies do DNA viruses with a replicative strategy for the synthesis of mRNAs have?

    <p>4</p> Signup and view all the answers

    What is antigenic shift?

    <p>The generation of progeny with antigenic properties completely different from the parental virus</p> Signup and view all the answers

    What is viral recombination?

    <p>The exchange of homologous stretches of genetic material between two virus strains</p> Signup and view all the answers

    What is the characteristic of RNA viruses in terms of recombination?

    <p>Recombination occurs during replication, when the viral enzyme can jump from one template strand to another</p> Signup and view all the answers

    What is the replication property of influenza virus type A that makes it prone to antigenic shift?

    <p>The segmented nature of its genome</p> Signup and view all the answers

    What is the frequency of recombination in viruses with a replicative enzyme that allows the exchange of the template strand?

    <p>High</p> Signup and view all the answers

    What is the incubation period?

    <p>The interval between the acquisition of infection and the onset of disease.</p> Signup and view all the answers

    What is the main modality of viral elimination?

    <p>Airway</p> Signup and view all the answers

    Which viruses can diffuse through the nervous route?

    <p>Herpes viruses</p> Signup and view all the answers

    What is the difference between incubation period and generation time?

    <p>Incubation period is the interval between acquisition of infection and transmission of infection to another individual, while generation time is the interval between the acquisition of infection and the onset of disease.</p> Signup and view all the answers

    What is latent infection?

    <p>The virus is detectable during the acute phase of replication, but it is no longer detectable as infectious virus if not in successive reactivation.</p> Signup and view all the answers

    What is the genome size of HIV?

    <p>9749 nucleotides</p> Signup and view all the answers

    What is the Immediate Precursor of HIV-1?

    <p>SIVcpz</p> Signup and view all the answers

    What is the estimated percentage of HIV isolates that represent recombinants between different subtypes?

    <blockquote> <p>20%</p> </blockquote> Signup and view all the answers

    Which HIV-1 mutations make the virus resistant to almost all NNRTIs?

    <p>Y181C and Y181I</p> Signup and view all the answers

    Which HIV genome region is the most prone to variation?

    <p>env gene</p> Signup and view all the answers

    What is the replication strategy used by HBV?

    <p>Reverse Transcriptase</p> Signup and view all the answers

    What is the mutation rate of HBV genome introduced by its Reverse Transcriptase?

    <p>1 mutation / 105 nucleotide</p> Signup and view all the answers

    How does the genome size of HBV compare to other animal DNA viruses?

    <p>Smallest</p> Signup and view all the answers

    What is the main difference between Parvovirus and Papovavirus in terms of DNA polymerase?

    <p>Papovavirus has its own DNA polymerase while Parvovirus uses the host cell's DNA polymerase</p> Signup and view all the answers

    Which group of RNA viruses includes Picornaviridae, Flaviviridae, Togaviridae, Caliciviridae, and Coronaviridae?

    <p>(+) sense RNA viruses</p> Signup and view all the answers

    What is the function of RNA-dependent RNA polymerase in viral replication of (+) RNA viruses?

    <p>To synthesize new molecules of RNA with positive polarity</p> Signup and view all the answers

    Which type of RNA viruses translates only the 5' portion of viral genome?

    <p>Togaviridae, Coronaviridae, and Caliciviridae</p> Signup and view all the answers

    What is the characteristic of single-stranded RNA with negative polarity?

    <p>It cannot serve as mRNA</p> Signup and view all the answers

    What is the main function of viral capsids?

    <p>To protect nucleic acids from damage</p> Signup and view all the answers

    What is the pericapsid composed of in some families of viruses?

    <p>Phospholipids and viral glycoproteins</p> Signup and view all the answers

    What is the role of capsid proteins in naked viruses?

    <p>To mediate binding and penetration into host cells</p> Signup and view all the answers

    What is the effect of UV radiation on nucleic acids?

    <p>It causes chemical alteration and mutations</p> Signup and view all the answers

    What is the function of viral glycoproteins in the pericapsid?

    <p>To act as virus receptor to target cells</p> Signup and view all the answers

    What is the process by which a viral infection causes a disease called?

    <p>Pathogenesis</p> Signup and view all the answers

    What is the unique genome organization of HBV that allows it to contain all the information necessary for its life cycle?

    <p>Extensive overlapping of open reading frames</p> Signup and view all the answers

    What is the consequence of deletions and stop codons in the S antigen?

    <p>Reduces binding affinity with neutralizing antibodies</p> Signup and view all the answers

    What is the practical implication of viral evolution?

    <p>Regulates the efficacy of natural and artificial immunity</p> Signup and view all the answers

    What is the replicative strategy of retroviruses?

    <p>Reverse transcription</p> Signup and view all the answers

    What is the estimated percentage of HIV isolates that represent recombinants between different subtypes?

    <p>Over 20%</p> Signup and view all the answers

    Which HIV-1 mutations make the virus resistant to almost all NNRTIs?

    <p>Y181C and Y181I</p> Signup and view all the answers

    Which HIV genome region is the most prone to variation?

    <p>env gene</p> Signup and view all the answers

    What is the estimated number of described HIV-1 Circulating Recombinant Forms?

    <p>Over 100</p> Signup and view all the answers

    What is the unique feature of HBV replication?

    <p>Uses Reverse Transcriptase for replication</p> Signup and view all the answers

    What is the period between the penetration of virus into cells and the maturation of viral progeny called?

    <p>Period of eclipse</p> Signup and view all the answers

    What is the ability of the virus to recognize specific receptors and infect specific cell types called?

    <p>Viral tropism</p> Signup and view all the answers

    What is the enzyme associated with RNA viruses with a negative polarity (-)?

    <p>RNA-dependent RNA polymerase</p> Signup and view all the answers

    What is the sensitivity of certain viruses to organic disinfectants due to?

    <p>Presence of pericapsid</p> Signup and view all the answers

    What is the difference between productive and abortive infection?

    <p>Production of viral particles</p> Signup and view all the answers

    What is the form of persistent infection in which the virus is not detectable except in cases of reinfection?

    <p>Latent infection</p> Signup and view all the answers

    What are the important events in viral pathogenesis?

    <p>Viral entry, viral replication, viral elimination, and viral dissemination</p> Signup and view all the answers

    Which of the following is a potential source of infection for hepatitis B, hepatitis C, and HIV?

    <p>Blood transfusion</p> Signup and view all the answers

    What determines the modality of transmission and the epidemiological characteristics of a viral infection?

    <p>The route of entry</p> Signup and view all the answers

    What creates a new entity, the infected cell, during virus-cell interaction?

    <p>The penetration of the virus into the host cell</p> Signup and view all the answers

    What is the double result of the spread of the virus and host survival?

    <p>Balance</p> Signup and view all the answers

    What is the term used to describe when a virus begins a new cycle of productive replication after a period of latency?

    <p>Relapse</p> Signup and view all the answers

    Which type of viruses are suspected to have some forms of latency?

    <p>RNA viruses</p> Signup and view all the answers

    What is the characteristic of chronic infections?

    <p>The virus is produced at much lower levels for a long time</p> Signup and view all the answers

    Which of the following viruses is NOT an example of chronic infections?

    <p>Influenza</p> Signup and view all the answers

    What is the most common route of dissemination for viruses?

    <p>Systemic blood (viremia)</p> Signup and view all the answers

    What is the least common route of transmission for viruses?

    <p>Through the genital route</p> Signup and view all the answers

    What is the mechanism by which viruses can migrate to find cells permissive for viral replication?

    <p>Through systemic blood (viremia)</p> Signup and view all the answers

    What is the characteristic of localized infections?

    <p>They are infections that remain confined to the tissues of the site of entry</p> Signup and view all the answers

    What is the most common type of transmission through which viruses can be subject to environmental and seasonal influences?

    <p>Through the respiratory route</p> Signup and view all the answers

    What is the replication strategy of viruses with (+) sense RNA genomes?

    <p>Their RNA genome acts as mRNA and is translated into a viral polyprotein</p> Signup and view all the answers

    Which type of cells can Parvovirus replicate in?

    <p>Cells that are in active proliferation</p> Signup and view all the answers

    What is the function of RNA dependent RNA polymerase in the replication of (+) sense RNA viruses?

    <p>Both of the above</p> Signup and view all the answers

    Which type of RNA virus is unable to serve as mRNA?

    <p>Riboviruses with negative RNA genome</p> Signup and view all the answers

    What is the difference in translation between Picornaviridae and Togaviridae, coronaviruses and caliciviruses?

    <p>Togaviridae, coronaviruses and caliciviruses translate the complete linear RNA genomes</p> Signup and view all the answers

    What is antigenic drift?

    <p>A continuous and gradual antigenic variation</p> Signup and view all the answers

    Which type of viruses are generally more genetically stable than RNA viruses?

    <p>DNA viruses</p> Signup and view all the answers

    What is antigenic shift?

    <p>A genetic reassortment resulting in extended changes in antigenic properties</p> Signup and view all the answers

    Which viruses are subject to antigenic drift?

    <p>Influenza virus, HIV, HBV, and HCV</p> Signup and view all the answers

    Which viral replicative enzyme is probably the most error-prone?

    <p>Reverse transcriptase of HBV and retroviruses</p> Signup and view all the answers

    What is the function of RNA-dependent RNA polymerase in viral replication?

    <p>It synthesizes new molecules of viral genome using (-) RNA strand</p> Signup and view all the answers

    What is the replicative strategy of Retroviruses?

    <p>They use reverse transcriptase to synthesize DNA from RNA template</p> Signup and view all the answers

    What is the concept of quasi-species in viral genetics?

    <p>It refers to the presence of a swarm of genetically different viral variants in an infected individual</p> Signup and view all the answers

    What is the replicative strategy of Reoviruses and Rotaviruses?

    <p>They have a segmented double-stranded RNA genome</p> Signup and view all the answers

    What is the role of integrase in Retroviral replication?

    <p>It catalyzes the integration of viral DNA into the host genome</p> Signup and view all the answers

    What is antigenic shift?

    <p>A process of viral recombination between two virus strains</p> Signup and view all the answers

    What is the cause of antigenic shift in influenza virus?

    <p>The segmented nature of its genome</p> Signup and view all the answers

    What is viral recombination?

    <p>Exchange of homologous stretches of genetic material between two virus strains</p> Signup and view all the answers

    What is the mechanism of viral recombination in RNA viruses?

    <p>Break and rejoin of homologous nucleic acid strands already synthesized</p> Signup and view all the answers

    Which virus has a high frequency of recombination?

    <p>HIV</p> Signup and view all the answers

    What is the main function of viral capsids?

    <p>To protect nucleic acids from physical and enzymatic damages</p> Signup and view all the answers

    What is pericapsid?

    <p>A structure present only in some families of viruses</p> Signup and view all the answers

    What is the function of capsid proteins in naked viruses?

    <p>To mediate the binding and penetration of the virus inside the host cell</p> Signup and view all the answers

    What is the role of viral glycoproteins in pericapsid?

    <p>To mediate the binding and penetration of the virus inside the host cell</p> Signup and view all the answers

    What is the major antigen of the virus in naked viruses?

    <p>Capsid proteins</p> Signup and view all the answers

    What is the period between the penetration of virus into cells and the maturation of viral progeny called?

    <p>Period of eclipse</p> Signup and view all the answers

    What is the ability of the virus to recognize specific receptors and infect specific cell types called?

    <p>Viral tropism</p> Signup and view all the answers

    Which enzyme is associated with the virion in RNA viruses with a negative polarity (-)?

    <p>RNA-dependent RNA polymerase</p> Signup and view all the answers

    What is the term used to describe when a virus enters the target cell but the life cycle cannot be completed?

    <p>Abortive infection</p> Signup and view all the answers

    Which protein present in the influenza virus envelope acts as an ion channel and causes the acidification of endocytic vesicles containing the virus?

    <p>M2 protein</p> Signup and view all the answers

    What is the difference between incubation period and generation time?

    <p>Incubation period is the interval between acquisition of infection and onset of disease, while generation time is the interval between onset of disease and transmission of infection to another individual.</p> Signup and view all the answers

    What is the main modality of viral elimination?

    <p>Airway</p> Signup and view all the answers

    Which viruses can diffuse through the nervous route?

    <p>Rhabdoviruses</p> Signup and view all the answers

    What is latent infection?

    <p>The virus is detectable during the acute phase of replication, but it is no longer detectable as infectious virus if not in successive reactivation.</p> Signup and view all the answers

    What is distant spread in viral infections?

    <p>It presupposes the lymphatic drainage of the virions and their release into the circulation.</p> Signup and view all the answers

    What is the replicative strategy for DNA viruses in the 1st group?

    <p>Viral gene expression is carried out by a DNA-dependent RNA polymerase in the nucleus</p> Signup and view all the answers

    What is the replicative strategy for DNA viruses in the 2nd group?

    <p>The entire replication cycle is completed in the cytoplasm</p> Signup and view all the answers

    What is the replicative strategy for DNA viruses in the 3rd group?

    <p>Synthesis of the complementary DNA strand is required for gene expression</p> Signup and view all the answers

    What is the replicative strategy for DNA viruses in the 4th group?

    <p>Viral gene expression is carried out by the cellular RNA polymerase II</p> Signup and view all the answers

    What is the difference in the number of steps for viral gene expression between Papovaviruses and Herpesviruses/Adenoviruses?

    <p>Papovaviruses have a 2-step gene expression process, while Herpesviruses and Adenoviruses have a 3-phase process</p> Signup and view all the answers

    What type of polymerase do DNA viruses require to replicate their genome?

    <p>DNA-dependent DNA polymerase</p> Signup and view all the answers

    What is the replicative strategy for DNA viruses with a partially double-stranded genome?

    <p>They use a RNA-dependent DNA polymerase to synthesize their genome</p> Signup and view all the answers

    What is the replicative strategy for poxviruses?

    <p>They use a RNA-dependent DNA polymerase to synthesize their genome in the cytoplasm</p> Signup and view all the answers

    What is the process for viral gene expression in Parvoviruses?

    <p>It requires synthesis of the complementary DNA strand followed by gene expression in the cytoplasm</p> Signup and view all the answers

    How many replicative strategies do DNA viruses follow for the synthesis of mRNAs?

    <p>4</p> Signup and view all the answers

    What is the role of RNA polymerase II in the replication of Herpesviruses, Adenoviruses, and Papovaviruses?

    <p>It carries out viral gene expression in the nucleus</p> Signup and view all the answers

    What is the most common genotype of Hepatitis C virus in chronically infected patients worldwide and in Europe?

    <p>Genotype 1</p> Signup and view all the answers

    What is the most efficient genotype of Hepatitis C virus in driving steatosis?

    <p>Genotype 3</p> Signup and view all the answers

    Which HCV genotype is significantly more prevalent among patients with liver cirrhosis and those with decompensated liver disease requiring liver transplantation?

    <p>Genotype 1b</p> Signup and view all the answers

    What is the error rate of RT enzyme during transcription of HIV genome?

    <p>1:2,000-10,000</p> Signup and view all the answers

    What is the mechanism responsible for the genetic variability of HCV?

    <p>High daily rate of viral production and lack of proofreading function of its polymerase</p> Signup and view all the answers

    What is the Immediate Precursor of HIV-1?

    <p>SIVcpz</p> Signup and view all the answers

    How many HIV-1 Circulating Recombinant Forms have been described?

    <p>100</p> Signup and view all the answers

    Which HIV-1 mutations make these viruses resistant to almost all NNRTIs?

    <p>Y181C and Y181I</p> Signup and view all the answers

    Which HIV genome region is the most prone to variation?

    <p>env gene</p> Signup and view all the answers

    What is the replication strategy of HBV?

    <p>Reverse transcription</p> Signup and view all the answers

    What are the important events in viral pathogenesis?

    <p>Viral entry, viral replication, dissemination to target organs, and elimination of the virus</p> Signup and view all the answers

    What is the most common route of viral penetration?

    <p>Respiratory route</p> Signup and view all the answers

    Which viruses can be transmitted through maternal-fetal transmission?

    <p>HIV, HBV, and HSV2</p> Signup and view all the answers

    What determines the modality of transmission and epidemiological characteristics of viral infection?

    <p>The route of entry</p> Signup and view all the answers

    What is the double result of the spread of the virus and host survival?

    <p>Balance</p> Signup and view all the answers

    What is the most common route of dissemination for viruses in the body?

    <p>Systemic blood</p> Signup and view all the answers

    Which route of viral penetration is influenced by social and economic conditions?

    <p>Gastrointestinal tract</p> Signup and view all the answers

    What is the least common route of viral transmission?

    <p>Genital route</p> Signup and view all the answers

    What type of individuals are particularly at risk for transmission through medical or surgical instruments, blood transfusions and blood products, organ transplantation?

    <p>Professionals, politransfused, drug addicts</p> Signup and view all the answers

    What is a potential source of infection for transmission through medical or surgical instruments, blood transfusions and blood products, organ transplantation?

    <p>Contaminated medical equipment</p> Signup and view all the answers

    What is antigenic drift?

    <p>A continuous and gradual antigenic variation</p> Signup and view all the answers

    Which virus has the most error-prone replicative enzyme?

    <p>Retroviruses</p> Signup and view all the answers

    What is antigenic shift?

    <p>A genetic reassortment that results in extended changes in antigenic properties</p> Signup and view all the answers

    Which type of virus is generally more genetically stable, DNA or RNA viruses?

    <p>DNA viruses</p> Signup and view all the answers

    Which viruses are examples of chronic infections?

    <p>HBV and HCV</p> Signup and view all the answers

    What is the purpose of the unique genomic organization of HBV?

    <p>To contain all the information necessary for its life cycle</p> Signup and view all the answers

    What can be the consequences of a mutation in an overlapping gene in HBV?

    <p>Severe consequences on the overlapping gene</p> Signup and view all the answers

    What is the pattern of lamivudine resistance mutations that correspond to reduced binding affinity with neutralizing antibodies?

    <p>I195M+E164D in the HBsAg</p> Signup and view all the answers

    What is the practical implication of viral evolution?

    <p>It can explain seasonal outbreaks, host change and pandemics</p> Signup and view all the answers

    What is the pathogenesis of a viral infection?

    <p>The process by which a viral infection causes a disease</p> Signup and view all the answers

    What is the function of RNA-dependent RNA polymerase in viral replication?

    <p>It synthesizes viral genome by using mRNAs as templates</p> Signup and view all the answers

    Which type of riboviruses have a segmented double-stranded RNA?

    <p>Reoviruses and Rotaviruses</p> Signup and view all the answers

    What is the function of reverse transcriptase in retroviruses?

    <p>It synthesizes DNA from an RNA template</p> Signup and view all the answers

    What is the concept of quasi-species in viral genetics?

    <p>It indicates the presence of genetically different viral variants in the same infected individual</p> Signup and view all the answers

    What is the role of integrase in retroviruses?

    <p>It catalyzes the integration of viral DNA into the host genome</p> Signup and view all the answers

    What is antigenic shift in influenza viruses type A?

    <p>A process of viral recombination between two virus strains</p> Signup and view all the answers

    Which type of viruses are prone to antigenic shift due to the segmented nature of their genome?

    <p>RNA viruses</p> Signup and view all the answers

    What is viral recombination?

    <p>A process of viral recombination between two virus strains</p> Signup and view all the answers

    What is the frequency of recombination in retroviruses?

    <blockquote> <p>20% of HIV isolates are recombinants between different subtypes</p> </blockquote> Signup and view all the answers

    How does viral recombination occur in RNA viruses?

    <p>During the synthesis of RNA</p> Signup and view all the answers

    What is the main reason for HCV's genetic variability?

    <p>The virus generates a high number of mutations per day</p> Signup and view all the answers

    What is the most frequent HCV genotype worldwide and in Europe?

    <p>Genotype 1</p> Signup and view all the answers

    Which HCV genotype is significantly more prevalent among patients with liver cirrhosis and those with decompensated liver disease requiring liver transplantation?

    <p>Genotype 1b</p> Signup and view all the answers

    What is the consequence of UV radiation on nucleic acids?

    <p>Increased rate of mutations</p> Signup and view all the answers

    What is the error rate of RT enzyme during transcription of HIV genome?

    <p>1:2,000-10,000 bases</p> Signup and view all the answers

    What is the main modality of viral elimination?

    <p>Airway</p> Signup and view all the answers

    What is the difference between incubation period and generation time?

    <p>Incubation period is the time between acquisition of infection and transmission of infection to another individual, while generation time is the time between acquisition of infection and onset of disease.</p> Signup and view all the answers

    Which viruses can diffuse through the nervous route?

    <p>Polio viruses</p> Signup and view all the answers

    What is a latent infection?

    <p>The virus is detectable during the acute phase of replication, but is no longer detectable as infectious virus if not in successive reactivation.</p> Signup and view all the answers

    What is distant spread in viral infections?

    <p>It presupposes the lymphatic drainage of the virions and their release into the circulation.</p> Signup and view all the answers

    What is the main difference between a relapse and a chronic infection?

    <p>A relapse is a new cycle of productive replication, while a chronic infection is characterized by the continuous presence of the virus.</p> Signup and view all the answers

    Which viruses are a classic example of viruses subjected to antigenic drift?

    <p>Influenza viruses</p> Signup and view all the answers

    What is the difference between a relapse and a phase of latency?

    <p>A relapse is a new cycle of productive replication, while a phase of latency is characterized by the continuous presence of the virus.</p> Signup and view all the answers

    Which viruses are suspected to have some forms of latency?

    <p>All of the above</p> Signup and view all the answers

    What are chronic infections characterized by?

    <p>The continuous presence of the virus, that continues to be produced even after the acute phase but usually at much lower levels</p> Signup and view all the answers

    What is the main difference between Parvovirus and Papovavirus in terms of DNA polymerase?

    <p>Papovavirus uses its own DNA polymerase while Parvovirus uses the DNA polymerase of the host cell</p> Signup and view all the answers

    What is the replication strategy of viruses with a (+) sense RNA genome?

    <p>They translate the complete linear RNA genome into a viral polyprotein which is subsequently cleaved into individual proteins by the viral protease</p> Signup and view all the answers

    What is the function of RNA dependent RNA polymerase enzyme in viruses with a (+) sense RNA genome?

    <p>It is responsible for the synthesis of new molecules of RNA with positive polarity that will be used as new molecules of viral genome and as mRNAs</p> Signup and view all the answers

    What is the difference in translation between Picornaviridae and Caliciviridae, Togaviridae, and Coronaviridae?

    <p>Picornaviridae translates only the 5’ portion of viral genome</p> Signup and view all the answers

    What is the main difference between Parvovirus and Papovavirus in terms of the type of cells they can infect?

    <p>Papovavirus can infect both replicating and non-replicating cells while Parvovirus can only infect replicating cells</p> Signup and view all the answers

    What is the unique replication strategy of HBV?

    <p>HBV uses Reverse Transcriptase for replication.</p> Signup and view all the answers

    What is the most variable virus type?

    <p>RNA viruses</p> Signup and view all the answers

    Which HIV genome region is the most prone to variation?

    <p>Env gene</p> Signup and view all the answers

    Which mutation of HIV-1 RT makes the virus resistant to almost all NNRTIs?

    <p>Y181C</p> Signup and view all the answers

    What is the estimated percentage of HIV isolates that represent recombinants between different subtypes?

    <blockquote> <p>20%</p> </blockquote> Signup and view all the answers

    What is the ability of a virus to recognize specific receptors and infect specific cell types called?

    <p>Viral tropism</p> Signup and view all the answers

    What is the enzyme associated with RNA viruses with a negative polarity (-)?

    <p>RNA-dependent RNA polymerase</p> Signup and view all the answers

    What is the period between the penetration of virus into cells and the maturation of viral progeny called?

    <p>Period of eclipse</p> Signup and view all the answers

    What is the consequence of the presence of pericapsid in certain viruses?

    <p>Sensitivity to organic disinfectants</p> Signup and view all the answers

    What is the main characteristic of an abortive infection?

    <p>No production of viral particles</p> Signup and view all the answers

    What is the route of dissemination for most viruses?

    <p>Systemic blood</p> Signup and view all the answers

    Which type of transmission is influenced by social and economic conditions?

    <p>Gastrointestinal route</p> Signup and view all the answers

    What is the less common but frequently used route of transmission?

    <p>Genital route</p> Signup and view all the answers

    What is the mechanism by which some viruses migrate to find cells permissive for viral replication?

    <p>Body fluids</p> Signup and view all the answers

    What is the characteristic of viruses entering through the skin?

    <p>They are capable of replication in cells residing in the superficial layers of the dermis</p> Signup and view all the answers

    What is the characteristic of chronic infections caused by viruses?

    <p>The virus is produced at much lower levels for a long time</p> Signup and view all the answers

    Which viruses are suspected to have some forms of latency?

    <p>Measles virus</p> Signup and view all the answers

    Which viruses have DNA replication intermediates and can experience relapse?

    <p>Adenovirus</p> Signup and view all the answers

    What is the outcome of a phase of latency in a virus cycle?

    <p>No viral activity</p> Signup and view all the answers

    Which viruses are examples of chronic infections?

    <p>HIV and HTLV</p> Signup and view all the answers

    What is the double result of the balance between virus spread and host survival in viral pathogenesis?

    <p>Elimination of the virus by the host organism</p> Signup and view all the answers

    Which of the following is a potential source of infection for hepatitis B, hepatitis C, and HIV?

    <p>Organ transplants</p> Signup and view all the answers

    What determines the modality of transmission and the epidemiological characteristics of viral infection?

    <p>The route of entry</p> Signup and view all the answers

    Which of the following is a less common but frequent route of viral penetration?

    <p>Skin lesions caused by insects, animals, medical and surgical instruments</p> Signup and view all the answers

    What is the most effective way to reduce the risk of HIV transmission from mother to child during perinatal transfer?

    <p>Early treatment after birth</p> Signup and view all the answers

    What is antigenic shift?

    <p>A process of viral recombination between two virus strains co-infecting the same cell</p> Signup and view all the answers

    What is the main reason for the high degree of genetic variability in HCV?

    <p>The virus produces a high number of mutations per day.</p> Signup and view all the answers

    What is the segmented nature of the influenza virus genome responsible for?

    <p>Antigenic shift</p> Signup and view all the answers

    What is the most common HCV genotype in chronically infected patients worldwide and in Europe?

    <p>Genotype 1</p> Signup and view all the answers

    What is viral recombination?

    <p>A process of viral recombination between two virus strains co-infecting the same cell</p> Signup and view all the answers

    Which HCV genotype is significantly more prevalent among patients with liver cirrhosis and those with decompensated liver disease requiring liver transplantation?

    <p>Genotype 1b</p> Signup and view all the answers

    What is the function of RNA-dependent RNA polymerase in viral replication?

    <p>To synthesize viral genome</p> Signup and view all the answers

    What is the replicative enzyme responsible for recombination in RNA viruses?

    <p>RNA polymerase</p> Signup and view all the answers

    What is the error rate of the RT enzyme during transcription of HIV genome?

    <p>1:10,000-50,000 bases</p> Signup and view all the answers

    What is the role of reverse transcriptase in retroviruses?

    <p>To synthesize viral genome from mRNA</p> Signup and view all the answers

    Which type of viruses have a high frequency of recombination between different subtypes?

    <p>Retroviruses</p> Signup and view all the answers

    What is the replicative capacity of HCV genotype 3 in driving steatosis compared to other genotypes?

    <p>It is more efficient than other genotypes.</p> Signup and view all the answers

    What is the purpose of the genomic RNA in riboviruses with diploid genome?

    <p>To be used for the double-stranded DNA synthesis</p> Signup and view all the answers

    What is the meaning of the term quasi-species in viral genetics?

    <p>The presence of genetically different viral variants in the same infected individual</p> Signup and view all the answers

    What is the function of integrase in retroviruses?

    <p>To integrate viral DNA into the host genome</p> Signup and view all the answers

    What is antigenic shift?

    <p>A genetic reassortment leading to extended changes in antigenic properties</p> Signup and view all the answers

    Which type of viruses are generally more genetically stable than RNA viruses?

    <p>DNA viruses</p> Signup and view all the answers

    What is antigenic drift?

    <p>A continuous and gradual antigenic variation induced by the host immune system</p> Signup and view all the answers

    Which viruses have a high frequency of spontaneous mutations?

    <p>RNA viruses</p> Signup and view all the answers

    What is the consequence of antigenic shift in influenza viruses?

    <p>The resulting virus can infect hosts already infected with the parental virus</p> Signup and view all the answers

    What is the main modality of viral elimination?

    <p>Airway</p> Signup and view all the answers

    What is the difference between incubation period and generation time?

    <p>Incubation period is the time between infection and onset of disease, generation time is the time between onset of disease and clearance of virus</p> Signup and view all the answers

    Which viruses can spread through the nervous route?

    <p>Rhabdoviruses</p> Signup and view all the answers

    What is the difference between superficial and systemic infections?

    <p>Superficial infections are limited to certain areas, while systemic infections affect the entire body</p> Signup and view all the answers

    What is the difference between latent and acute infections?

    <p>Latent infections are detectable during the replication phase, but not as infectious virus if not in successive reactivation, while acute infections are detectable as infectious virus during the replication phase</p> Signup and view all the answers

    What is the replicative strategy of poxviruses?

    <p>Replication occurs in the cytoplasm with the help of viral DNA polymerase.</p> Signup and view all the answers

    What is the replicative strategy of parvoviruses?

    <p>Replication occurs in the nucleus with the help of RNA polymerase II.</p> Signup and view all the answers

    What is the replicative strategy of HBV?

    <p>Replication is completed in the cytoplasm with the help of RNA-dependent DNA polymerase.</p> Signup and view all the answers

    How many replicative strategies do DNA viruses follow for the synthesis of mRNAs?

    <p>4</p> Signup and view all the answers

    Which enzyme is required for the replication of HBV genome?

    <p>Reverse transcriptase</p> Signup and view all the answers

    What is the replication strategy for Parvovirus and Papovavirus?

    <p>They use the DNA polymerase of the host cell</p> Signup and view all the answers

    Which type of cells can Parvovirus replicate in?

    <p>Progenitors of the red blood cells</p> Signup and view all the answers

    What is the replication strategy for RNA viruses with a positive polarity?

    <p>The complete linear RNA genomes act as mRNA and is translated into a viral polyprotein</p> Signup and view all the answers

    What is the function of RNA dependent RNA polymerase in RNA virus replication?

    <p>Synthesis of new molecules of RNA with positive polarity that will be used as new molecule of viral genome and as mRNAs</p> Signup and view all the answers

    What is the genome polarity of riboviruses with negative RNA genome?

    <p>Negative</p> Signup and view all the answers

    What is the consequence of deletions and stop codons in the S antigen of HBV?

    <p>They induce oxidative stress in hepatocytes</p> Signup and view all the answers

    What is the role of viral variability in the efficacy of immunity against viruses?

    <p>It is strain- or type-specific and therefore of limited clinical relevance</p> Signup and view all the answers

    What is the consequence of a mutation that has little effect on one viral protein but severe consequences on an overlapping gene in HBV?

    <p>The mutation is not selected</p> Signup and view all the answers

    What is the form of viral infection in which the virus is not detectable except in cases of reinfection?

    <p>Latent infection</p> Signup and view all the answers

    What is the pattern of lamivudine resistance mutations in HBV that strongly reduce the binding affinity with neutralizing antibodies including those induced by the vaccine?

    <p>M204V+L180M+V173L in RT correspond to I195M+E164D in the HBsAg</p> Signup and view all the answers

    What is the main function of viral capsids?

    <p>To protect nucleic acids from physical and enzymatic damages</p> Signup and view all the answers

    What is the pericapsid?

    <p>A structure present only in some families of viruses that contains phospholipids and viral glycoproteins</p> Signup and view all the answers

    What is the role of naked virus capsid proteins?

    <p>To mediate the binding and penetration of the virus inside the host cell</p> Signup and view all the answers

    What is the significance of viral glycoproteins in pericapsid?

    <p>They act as virus receptors to target cells</p> Signup and view all the answers

    What is the purpose of viral genome packaging?

    <p>To protect the viral genome and ensure efficient transmission to other cells</p> Signup and view all the answers

    Study Notes

    RNA-dependent RNA Polymerase and Viral Replication

    • Synthesizes RNA from an RNA template, essential for viruses with RNA genomes.
    • Critical for the replication of RNA viruses, facilitating the generation of viral genomes and mRNA.

    Segmented Double-stranded RNA Viruses

    • Example includes the Reoviruses, which have segmented RNA genomes that allow reassortment during co-infection.

    Retrovirus Replication

    • Retroviruses use reverse transcription to convert RNA into DNA, integrating it into the host genome for replication.
    • Utilize host cellular machinery for viral protein synthesis and assembly.

    Quasi-species Concept

    • Refers to the population of closely related viral genomes that exhibit genetic diversity, resulting from replication errors.
    • Important for understanding viral evolution and response to treatment.

    Viral Capsids and Their Functions

    • Protect viral nucleic acids from enzymatic damage and environmental factors.
    • Facilitate attachment to host cells and entry into the host.

    Composition of Pericapsid

    • Comprised of lipid membranes or additional protein layers, providing an extra protective barrier for some viruses.

    Capsid Proteins in Naked Viruses

    • Essential for maintaining virus structure, protecting the genome, and facilitating attachment and entry into host cells.

    Enzymatic Protection Offered by Viral Capsids

    • Shield nucleic acids from DNases and RNases, maintaining viral integrity.

    (+) Sense RNA Genome Replication Strategy

    • Functions directly as mRNA, immediately translated by host ribosomes to produce viral proteins.
    • RNA-dependent RNA polymerase synthesizes a complementary RNA strand for viral genome replication.

    Parvovirus Cell Replication

    • Exclusively replicates in dividing cells, requiring the host's cellular machinery for nucleic acid synthesis.

    RNA Polymerase in (+) Sense RNA Viruses

    • Synthesizes a complementary (-) RNA strand, serving as a template for new (+) RNA genomes.

    (-) Sense RNA Genome Replication Strategy

    • Requires conversion to (+) RNA before translation, with RNA-dependent RNA polymerase needed for this process.

    HCV Genetic Variability

    • High mutation rate due to error-prone replication, creating numerous viral variants which complicate treatment.

    HCV Genotype Prevalence

    • Genotype 1 is the most frequently occurring globally and in Europe, particularly subtype 1b which has significant clinical implications.

    HIV Reverse Transcriptase Error Rate

    • High error rate contributes to genetic diversity, with around 20% of isolates showing recombinant characteristics.

    Most Prone HIV Gene Variation

    • The env gene exhibits the highest mutation rates, affecting the virus’s structure and immune recognition.

    HBV Unique Replication Strategy

    • Utilizes reverse transcription to replicate its genome, utilizing a small RNA intermediate.

    HIV Inhibitors Targeting Attachment

    • Entry inhibitors that block the binding of the virus to host cells during infection.

    Antigenic Drift and Shift

    • Drift: Minor changes in viral antigens due to mutations; shift: major changes, often through reassortment of segmented genomes.

    Viral Replicative Enzymes and Mutation Rates

    • RNA viruses generally have higher mutation rates than DNA viruses, impacting their variability and adaptability.

    Viral Pathogenesis Events

    • Key events include attachment, penetration, replication, release of progeny, and host damage.

    Transmission Routes Influenced by Socioeconomic Conditions

    • Modes such as sexual and blood-borne transmission can vary based on these factors.

    Viral Incubation Period

    • The time between virus entry into the host and the onset of symptoms can vary widely among different viruses.

    Latent Infections

    • Characterized by periods of inactivity, viruses may reactivate under favorable conditions.

    Poxvirus Replicative Strategy

    • Replicate entirely in the cytoplasm, unlike most DNA viruses that replicate in the nucleus.

    HBV Replication and Reverse Transcriptase

    • Utilizes a reverse transcriptase enzyme to convert RNA to DNA during replication.

    Importance of Viral Evolution

    • Facilitates adaptation to host immune responses and enhances survival, complicating vaccine and antiviral development.

    Routes of Viral Penetration

    • Commonly include respiratory, oral-fecal, and sexual transmission pathways.

    Chronic Infections Examples

    • Viruses like HIV and Hepatitis B can establish persistent infections, often leading to long-term health issues.

    Relapse During Viral Infections

    • Re-emergence of viral activity, can occur after periods of inactivity, particularly in chronic infections.

    Modulation of Viral Entry and Spread

    • Viruses can utilize various mechanisms to enhance host accessibility, impacting pathogenesis and transmission dynamics.

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    Viral Replication Cycle PDF

    Description

    Test your knowledge on viral evolution and genetic modification in this quiz. Explore the mechanisms behind point mutations, deletions, insertions, and reassortment, and their impact on viral diversity and drug resistance. Keywords: viral evolution, genetic modification, mutations, drug resistance.

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