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GMS Exam 1 Questions And
Answers
Shared feature among Coronaviruses? Ans- They all produce a nested set of subgenomic mRNAs. True or False: The HE spike of coronaviruses is responsible for fusion of the viral and host membranes. Ans- False True or False: Coronaviruses bud at the plasma membrane. Ans- False Where do CoV bud? Ans- in intermediate compartments (IC) within the cell True or False: Acute respiratory distress during a SARS infection is likely caused by a cytokine storm. Ans- True What is the accepted reservoir host of SARS? Ans- Bats Which of the following viruses is not a member of the Flaviviridae family?
- Rotavirus
- Yellow Fever Virus
- West Nile Virus
- Hep C Virus Ans- Rotavirus Shared feature between flaviviruses and togaviruses? Ans- Many viruses in both families are arboviruses. Which of the following statements about viral fusion is incorrect?
- The low pH of the endosome induces a conformational change in the virion that exposes the fusion peptide.
- The viral fusion glycoprotein is always the same glycoprotein that binds the host receptor.
- After fusion of the viral membrane with the endosomal membrane, the viral genome is released into the cytoplasm. Ans- The viral fusion glycoprotein is always the same glycoprotein that binds the host receptor. Flaviviruses and togaviruses both generate polyproteins that thread into and out of the ER membrane; what is the main purpose of this? Ans- To localize the viral glycoproteins in the ER lumen where they can then move to the Golgi and become glycosylated. Which feature of togavirus/alphavirus virions is incorrect? A- They have flower-shaped spikes extending off of the surface. B- The envelope is icosahedral, but the capsid is disorganized. C- Each petal associates with one capsid protein underneath the lipid bilayer. D- Each petal of the flower is comprised of a heterodimer of the two glycoproteins (E1 and E2). Ans- The envelope is icosahedral, but the capsid is disorganized. What recruits host translation initiation factors to the 5' end of calicivirus genomes? Ans- The viral VPg protein How are the norovirus structural proteins synthesized? Ans- They are translated from a subgenomic mRNA produced late in the replication cycle. Which of the following features is true regarding norovirus virions? A- The minor structural protein VP2 resides only inside the virion. B- They are extremely stable over a broad pH range. C- The tips of the arches protruding off the surface are the most hypervariable region of the virion. D- All of these Ans- All of these What are 3 features of Norovirus virions? Ans- 1. They are extremely stable over a broad pH range.
- The tips of the arches protruding off the surface are the most hypervariable region of the virion.
- The minor structural protein VP2 resides only inside the virion.
What factor recruits host translation initiation factors to the 5' end of picornavirus genomes to initiate protein production? A- A methylated guanosine cap B- The host ribosome itself C- A viral VPg protein D- An internal ribosome entry site (IRES) Ans- An internal ribosome entry site (IRES) Which poliovirus vaccine is in common use in the United States today?
- IPV (inactivated polio vaccine)
- OPV (oral live attenuated polio vaccine) Ans- IPV (inactivated polio vaccine) After the Poliovirus is contained in an area, which form of the vaccine is used: the inactivated or the live form? Ans- the inactivated polio vaccine (IPV) Which of these is not an example of immunopathology? A- Antibody-dependent enhancement of viral infection B- Virus antagonism of the interferon signaling pathway C- Viral induction of pyrogenic cytokines that stimulate fever D- Generation of immune complexes during chronic infections Ans- Virus antagonism of the interferon signaling pathway If you are exposed to virus particles when your sick neighbor sneezes close to you, which form of viral transmission does this represent? Ans- Horizontal Would you expect virus in nature, or virus used in the laboratory, to be more genetically diverse? Ans- in nature Reassortment can only occur for which class of virus? Ans- Viruses with segmented genomes
Which of the following is not a reason that RNA viruses have a higher rate of mutation than DNA viruses? A- They have low-fidelity polymerases B- Their polymerases lack proof-reading activity C- They replicate entirely in the cytoplasm D- Their genomes are much smaller so the replication rate is much quicker Ans- They replicate entirely in the cytoplasm. True or False: The skin is the most common site of viral infections. Ans- False Which of the following represent barriers to viral infections of the gastrointestinal tract?
- bile detergents
- all of these
- mucosal IgA
- acid pH of the stomach
- thick layer of mucus Ans- all of these What are 4 barriers to viral infections of the GI tract? Ans- 1. mucosal IgA
- thick layer of mucus
- acid pH of the stomach
- bile detergents True or False: All virus infections of host cells result in killing of the infected cell. Ans- False Which term describes an infection where the virus can spread to many different organs in the body? Ans- systemic infection Which of the following does not represent a mechanism by which viruses can disseminate to secondary tissues? A- Cell-associated viremia once a virus infects a migratory cell
Retroviruses are unique viruses because they require reverse transcriptase (RT), which is packaged with the genome. For most retroviruses, the (+)RNA genome is packaged, and then converted to ssDNA (when?): Ans- after entry into a new cell If you were to measure infectious virus titers 2 hours after infection, you would most likely observe a: Ans- significant drop in virus titer Immunofluorescence is a useful means to directly detect viral particles or viral in tissue or cell samples. Ans- antigens PCR is an excellent way to directly detect viral genomes or viral transcripts, but requires an educated guess for testing purposes because of the need to use: Ans- sequence- specific primers PCR is an excellent way to detect viral genomes or viral transcripts in tissue, cell or fluid samples, but requires an educated guess for testing purposes because of the need to use: A- viral antigens B- sequence-specific RNA C- DNA nucleotides D- sequence-specific primers E- protein-specific antibodies Ans- sequence-specific primers Immunofluorescence is a useful means to detect viral particles or viral in tissue or cell samples.
- RNA
- antigens
- envelopes
- DNA
- antibodies Ans- antigens If you were to measure infectious virus titers 2 hours after infection, you would most likely observe a: A- 1000-fold increase in virus titer B- 100,000-fold increase in virus titer
C- significant drop in virus titer D- small increase in virus titer E- no change until an increase is observed Ans- significant drop in virus titer Retroviruses are unique viruses because they require reverse transcriptase (RT), which is packaged with the genome. For most retroviruses, the (+)RNA genome is packaged, and then converted to ssDNA:
- during genome replication
- immediately upon packaging
- during capsid maturation
- as soon as RT is available
- after entry into a new cell Ans- after entry into a new cell The most important enzyme for RNA virus replication is the RDRP (RNA-dependent RNA polymerase). In order for negative strand (-) RNA viruses to replicate in a newly infected cell, they must:
- incorporate RDRP into the viral particle
- hijack host RDRP
- express RDRP immediately after entry
- first replicate the (-)RNA genome
- first make a (+)RNA genome copy Ans- incorporate RDRP into the viral particle The basic component of a virion that is required to protect the nucleic acid genome is the: Ans- capsid Enveloped viruses are susceptible to many environmental stresses such as dehydrating agents due to the sensitivity of their:Ans- lipid membrane Each triangular face of a capsid is usually made of proteins. Ans- 3 The Baltimore classification system, the most commonly used virus classification system, groups viruses based on (2): Ans- genome structure & reverse transcriptase
What is important for enveloped viruses during transmission? Ans- They must stay wet. What is the symmetry ratio exhibited by Icosahedral viruses? Ans- 5:3:2 symmetry (six 5-fold axes, ten 3-fold axes, and fifteen 2-fold axes) How many faces make up an Icosahedral capsid? Ans- 20 faces How many proteins usually make up one face of a capsid? Ans- 3 proteins What is the least number of proteins that can make up a capsid? Ans- 60 total proteins What is unique about Bacteriophage capsids? Ans- They can exhibit both icosahedral and helical structures. What are the 7 types of viruses used in the Baltimore Classification System? Ans- 1. ssDNA
- dsDNA
- dsRNA
- (+) RNA
- (-) RNA
- Retroviruses (w/ RT)
- ss/dsDNA (w/ RT) How many species of viruses are there? Ans- 2285 species of viruses How many families of viruses are there? Ans- 87 families of viruses What are the 9 general stages of viral infection? Ans- 1. Adsorption
- Entry
- Uncoating
- Translating Early Genes
- Replication of Genome
- Translation of Late Genes
- Assembly
- Packaging
- Release What does the replication strategy of each virus depend on? Ans- the form of its genome During virus growth, what happens to the number of viruses during 'Disassembly'? Ans- the number of viruses sharply decreases During virus growth, what happens to the number of viruses during 'Replication'? Ans- the number of viruses stays the same During virus growth, what happens to the number of viruses during 'Assembly'? Ans- the number of viruses sharply increases What is Immunofluorescence? Ans- A direct viral detection technique that uses virus‐ specific antibodies to detect a specific viral protein, usually in a tissue section biopsy or cells. What does ELISA stand for? Ans- Enzyme‐linked immunosorbent assay What is ELISA? Ans- A direct viral detection technique that uses virus‐specific antibodies to detect virus particles or secreted viral proteins in fluid. When is Electron Microscopy used? Ans- to detect viral particles in lesions What are the 4 techniques used for direct detection of viruses? Ans- 1. Electron Microscopy
- Immunofluorescence
What is the consequence of the dermis and sub-dermal tissues being highly vascularized? Ans- infections may disseminate How is the skin a barrier to infection? Ans- this outer layer of dead, keratinized cells cannot support viral infection What is the most common route of viral entry? Ans- the respiratory tract Why is the respiratory tract the most common route of viral entry? Ans- The respiratory tract has a huge, absorptive area and high turnover. What is the major portal of entry for pathogens in the GI tract? Ans- M cells What is the cytopathic effect? Ans- the structural changes in the host cells that are caused by viral invasion What is an abortive infection? Ans- an infection that does not result in the generation of infectious particles What characterizes a chronic infection? Ans- constant production of virus and a long incubation period What is an example of a recurrent virus? Ans- herpes simplex What is a latent virus? Ans- an asymptomatic infection that does not result in viral progeny What is the effect of transformation due to viral infection? Ans- abnormal cell growth Define tissue tropism: Ans- the spectrum of tissues infected by a virus Define dissemination: Ans- spreading beyond the primary site of entry
What is a systemic infection? Ans- an infection that affects many organs What is the consequence of basolateral release of virions? Ans- it could result in viral dissemination What are the 2 routes of viral dissemination? Ans- 1. hematogenous spread
- neural spread What is hematogenous spread? Ans- spreading by way of the bloodstream What is the difference between primary viremia and secondary viremia? Ans- Primary viremia refers to the initial spread of virus in the blood from the first site of infection. Secondary viremia occurs when primary viremia has resulted in infection of additional tissues via bloodstream, in which the virus has replicated and once more entered the circulation. What is the difference between passive viremia and active viremia? Ans- Passive viremia is the introduction of viruses in the bloodstream without the need of active viral replication, whereas active viremia is caused by the replication of viruses which results in viruses being introduced into the bloodstream. What is an example of cell-associated hematogenous spread? Ans- when a virion adheres to RBCs or platelets before replicating What is neural spread via peripheral nerve? Ans- viruses that spread from the primary site of infection by entering local nerve endings What is an example of passive viremia? Ans- direct inoculation by insects Which results in higher viral shedding: primary viremia or secondary viremia? Ans- secondary viremia What is an example of secondary viremia? Ans- rabies
Which has a higher spontaneous mutation rate: DNA or RNA? Ans- RNA Why does RNA have a higher spontaneous mutation rate? Ans- It is due to the poor fidelity of polymerase, the rapid rate of genome replication, and the lack of a proofreading mechanism. Which has more genetic stability: DNA or RNA? Ans- DNA Which has more genetic adaptability: DNA or RNA? Ans- RNA What is the goal during induced mutations? Ans- single nucleotide changes Forward genetics uses to find. Ans- Phenotype; Genotype What is reverse genetics? Ans- using the genotype to find the phenotype What is the nucleocapsid symmetry of Coronaviruses? Ans- helical Coronaviruses are (enveloped/ naked capsids) and have what type of genome? Ans- CoV are enveloped and have a positive-sense ssRNA What is responsible for the morphology of CoV? Ans- the S proteins (spikes) SARS requires which cell receptor for binding? Ans- ACE What is the shorter "spike-like" protein that some Coronaviruses have? Ans- HE proteins CoV are frequently associated w/ what? Ans- the common cold CoV generally infect the tract, but can also infect the tract. Ans- they usually infect the respiratory tract, but can infect the GI tract
Rhinoviruses are frequently associated w/ what? Ans- the common cold What is unique about Coronaviruses? Ans- they are large and they exhibit "nested" transcription Where are the non-structural protein genes located within the genome of CoV? Ans- at the 5' end What is special about subgenomic mRNAs? Ans- many different proteins can be created from the same mRNA strand How are subgenomic mRNAs created? Ans- Subgenomic mRNAs are created when transcription begins at the 3' end of the template strand (or 5' of the to-be-newly synthesized template) and begins to copy towards the 5' end of the template strand before "jumping" to the end of the template and copying the last nucleotides of the 5' end of the template, (finishing the 3' tail for the newly created strand). What do the products of "nested" transcription look like? Ans- the translated strand will have a similar 5' end to varying degrees with the original template (depending on which part of the template the transcription jumped over) and a similar 3' end to the template. What is the genome for Influenzaviruses? Ans- single-stranded (-) RNA True or False: Influenzaviruses are segmented. Ans- True The nucleocapsid symmetry of all negative-sense ssRNA is. Ans- helical monocistronic- Ans- an mRNA segment that encodes for a single viral protein Where are RNA segments spliced? Ans- in the nucleus Influenzaviruses have mRNA segments. Ans- 8
How do Influenzaviruses gain entry into host cells? Ans- the HA glycoproteins bind to the receptors on the surface of the host cell where cell-mediated endocytosis follows and fusion with the endosomes occurs After Influenzaviruses gain entry into a host cell via cell-mediated endocytosis, what do they do first? Ans- release their segmented genomes into the cytoplasm Where do Influenzaviruses replicate within the host cell Ans- Influenzaviruses replicate within the nucleus. Influenzaviruses replicate in the nucleus to yield (+)mRNA; where is this positive-sense mRNA translated? Ans- in the cytoplasm Hemagglutinin binds what type of receptors? Ans- HA proteins bind sialic acid-containing receptors. Is Neuraminidase involved in the entry process of Influenzaviruses? Ans- No During the budding process of Influenzaviruses, the progeny virions get "stuck" to sialic acid-containing receptors on the surface of the host cell. What cleaves these sialic acid-containing receptors so that the progeny Influenzaviruses can complete the budding phase? Ans- Neuraminidase glycoproteins (NA) M2 proton channels form to create small pores in the envelope of Influenzaviruses? Ans- tetramers What is the role of the M2 proton channel in Influenzaviruses? Ans- this proton channel allows protons (H+) to flow inside the virion and facilitate the release of the nucleocapsid into the cytoplasm Which anti-influenza drug blocks M2 channel activity? Ans- Amantadine Where are the highly conserved regions of the Influenzavirus genome? Ans- at their 5' and 3' ends
Why is a lot of "shuttling" needed for Orthomyxoviruses? Ans- BC they replicate in the nucleus and continue the other stages of viral infection in the cytoplasm How do Influenzaviruses gain their 5' "cap"? Ans- Influenzaviruses steal their 5' caps from cellular pre- mRNAs inside the nucleus. How is the Poly-A "tail" generated in Influenzaviruses? Ans- During transcription, PB1 uses a "stuttering" technique and continuously adds complementary A's to the poly-U's that it stutters back to and reads several times over. True or False: Splicing of the mRNA segments 7 and 8 occurs frequently. Ans- False Influenzavirus proteins that have just been translated in the cytoplasm are shuttled back into the nucleus to aid in. Ans- replication How does NS2 aid the export of Influenzavirus nucleocapsids from the nucleus? Ans- NS2 has a nuclear export signal For Influenzaviruses, what is the most abundant viral protein in infected cells? Ans- NS What is the role of NS1 for Influenzaviruses? Ans- NS1 has multiple functions to shut down the host cell Which Influenzavirus protein interferes with the polyadenylation of cellular mRNAs? Ans- the protein NS Type I Interferon is suppressed by which Influenzavirus protein? Ans- NS Where does glycosylation take place? Ans- the Golgi What are the secondary infections caused by Influenzaviruses due to? Ans- Influenzaviruses compromise the single layer of cells in the respiratory tract that consist of goblet cells and ciliated cells.
