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GMS Exam 1 Questions And Answers
Typology: Exams
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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?
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?
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?
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.
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:
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
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
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.