Virology Exam #1

SARS-CoV-2 has an estimated k of 0.1. That means that: a. 10% of infected people are causing 80% of new infections b. 10% of infected people are causing 10% of new infections c. 0.1 % of infected people are causing 80% of new infections d. 0.1 % of infected people are causing 10% of new infections

a. 10% of infected people are causing 80% of new infections

Viruses are obligate intracellular parasites. Why? a. Because viral genome replication needs host cell enzymes or substrates (for example nucleotides), and viral proteins are synthesized by host cell ribosomes b. Because viral genome replication always needs host cell enzymes c. Because viral proteins are synthesized by host cell ribosomes d. Because the virion is only stable inside the host cell

a. Because viral genome replication needs host cell enzymes or substrates (for example nucleotides), and viral proteins are synthesized by host cell ribosomes

Which of the following allow the innate immune system to distinguish microbes from self? a. Cytoplasmic helicases and TLRs

a. Cytoplasmic helicases and TLRs

Which is not a universal rule of viral DNA synthesis? a. DNA synthesis is always 3' to 5' b. Replication starts at specific template sites called origins c. The 3'-OH end of the last nucleotide of the chain is covalently bound to the 5'-P end of the dNTP being added and so forth d. Requires DNA-dependent DNA polymerase

a. DNA synthesis is always 3' to 5'

Rous sarcoma virus, a retrovirus, must do what before transcription of mRNA can occur? a. Production of dsDNA by RT which then integrates into the host cell genome b. Production of ssDNA by RT which then integrates into the host cell genome c. Production of dsDNA by RT which but integration into the host cell genome is not required d. Production of ssDNA by RT which but integration into the host cell genome is not required

a. Production of dsDNA by RT which then integrates into the host cell genome

The proteins LT (SV40), E7 (HPV-16 or 18) and E1A (AD5) sequester the cellular protein Retinoblastoma (Rb). Why? a. Rb inhibits expression of genes required for DNA synthesis and entry into S phase b. Rb enhances expression of genes required for DNA synthesis and entry into S phase c. Rb is the DNA polymerase d. Rb is an helicase

a. Rb inhibits expression of genes required for DNA synthesis and entry into S phase

Which is a universal rule of RNA-directed RNA synthesis? a. RdRp may initiate de novo or require a primer b. RNA synthesis initiates randomly on the RNA template c. RNA is synthesized in the 3' to 5' direction d. RNA synthesis is always template-directed

a. RdRp may initiate de novo or require a primer

A common fate of permissive host cells for non-enveloped viruses is cell death. a. True b. False: for enveloped viruses c. False: cell detachment d. False: cell quiescence

a. True

INFs are pro-inflammatory cytokines. a. True b. False: anti-inflammatory c. False: chemokines d. INFs and cytokines are not related at all

a. True

Some viruses require virion maturation in the form of protein cleavage after being released from the host cell. Without that maturation, they cannot infect more cells. a. True b. False: all viruses are ready to infect immediately after release c. False: protein cleavage after release never happens d. False: virion maturation is an outdated concept

a. True

The fraction of cells infected by a given number of viral particles is dependent on the MOI a. True b. False: receptor number only c. False: viral particle number only d. False: cell number only

a. True

The inflammatory response, as well as the antiviral response, are part of the innate immune response. a. True b. False: inflammation and innate immunity are not related at all c. False: the antiviral response and innate immunity are not related at all d. False: they are part of the adaptive immune system

a. True

Viral genomes can be grouped into seven classes - dsDNA, gapped ds DNA, ss + DNA, dsRNA, + RNA, + RNA with dsDNA intermediate, and - RNA. a. True b. False: six classes - dsDNA, gapped ds DNA, ss DNA, dsRNA, + RNA, and - RNA c. False: 2 classes - RNA and DNA d. False: five classes - dsDNA, ss + DNA, dsRNA, + RNA, and - RNA

a. True

Viral size is typically in the nanometer range while bacterial size is typically in the low micrometer range (1-2 µm) and human cell size is typically 10-20µm. a. True b. False: viruses are typically in the low micrometer range, just like bacteria c. False: human cells are typically in the low micrometer range, just like bacteria d. False: viral size in typically in the picometer range

a. True

Viruses can increase glycolysis and the TCA cycle for ATP production or use glycolysis and TCA cycle intermediates to shunt metabolism towards macromolecule biosynthesis (amino acids, fatty acids, nucleotides) a. True b. False: viruses can increase glycolysis but not inhibit glycolysis c. False: glycolysis is not connected to nucleotide synthesis at all d. False: the TCA cycle is not connected to fatty acid synthesis at all

a. True

dsRNA viruses must make mRNA, which is then used for both protein synthesis and dsRNA generation a. True b. False: dsRNA viruses must make dsDNA c. False: dsRNA viruses do not need to replicate the genome d. False: dsRNA viruses can use the + strand as mRNA

a. True

ss - RNA viruses must make mRNA and ss + RNA which serves as a template for genome production a. True b. False: ss - RNA viruses must make dsDNA c. False: ss - RNA viruses must make ss - RNA to generate mRNA d. False: ss - RNA viruses can use the - strand as mRNA

a. True

Gapped dsDNA genomes must complete the gap before producing mRNA or duplicating the genome a. True: for example, Hepadnaviridae and the Hepatitis B virus b. False: they can produce mRNA, but not duplicate the genome c. False: they can duplicate the genome but not produce mRNA d. False: they can do both without completing the gap

a. True: for example, Hepadnaviridae and the Hepatitis B virus

Knowing the nature of the viral genome, it is possible to deduce the basic steps that need to happen for viral mRNA production a. True: for example, viruses with + RNA must produce -RNA, or -DNA followed by dsDNA, in order to produce mRNA b. True: for example, viruses with + DNA must produce - RNA, in order to produce mRNA c. False: viruses with +RNA already have mRNA, since + RNA is always mRNA d. False: nobody knows the basic steps that lead to viral mRNA production

a. True: for example, viruses with + RNA must produce -RNA, or -DNA followed by dsDNA, in order to produce mRNA

When developing new vaccines, researchers want a good balance between Th1 and Th2 responses. a. True: good vaccines will be good inducers of antibody production but also good inducers of cytotoxic T cell responses b. Mostly Th2 c. Mostly Th1 d. Th1 and Th2 responses have nothing to do with vaccine development

a. True: good vaccines will be good inducers of antibody production

Virus-induced changes in glucose metabolism can trigger type 2 diabetes. a. True: increased production of glucose by the liver b. False: glucose uptake by tissues is always increased c. False: the liver always increases glucose uptake and glycolysis d. False: blood glucose levels and type 2 diabetes are not related

a. True: increased production of glucose by the liver

R0 = tau x C x D. a. True: the basic reproductive number is equal to the product between the probability of infection given contact, average duration of contact between infected and uninfected host and duration of infectivity b. True: the basic infective number is equal to the product between the probability of infection, average duration of contact between infected and uninfected host and duration of infectivity c. False: the basic reproductive number is equal to the fraction between the probability of infection given contact and average duration of contact between infected and uninfected host times duration of infectivity d. False: the basic infective number is equal to the fraction between the probability of infection given contact and average duration of contact between infected and uninfected host times duration of infectivity

a. True: the basic reproductive number is equal to the product between the probability of infection given contact, average duration of contact between infected and uninfected host and duration of infectivity

The RNA world is a theory that states that RNA existed before DNA. This contributes to the idea that viruses are really old. a. True: the only RNA genomes on the planet today are viral b. True: the only DNA genomes on the planet today are viral c. False: viruses are relatively recent in evolution d. False: viral genomes are never made of RNA

a. True: the only RNA genomes on the planet today are viral

RT has revolutionized molecular biology. Which statement about the enzyme is not correct? a. Unique to retroviruses b. Packaged in the retroviral particle c. Has RNaseH activity d. It reverses the flow of genetic information

a. Unique to retroviruses

Which DNA genome, on entry into the cell, can be immediately copied to mRNA? a. dsDNA b. gapped dsDNA c. circular ssDNA d. linear ssDNA

a. dsDNA

The PI3K pathway can be activated by viral attachment, leading to: a. Cell death and autophagy b. Actin remodeling and endocytosis c. Apoptosis d. Necroptosis

b. Actin remodeling and endocytosis

Helical symmetry can be described as: a. Coat protein molecules engage in non-identical, non-equivalent interactions with one another and with the viral genome to allow construction of a large, stable structure from a single protein subunit b. Coat protein molecules engage in identical, equivalent interactions with one another and with the viral genome to allow construction of a large, stable structure from a single protein subunit c. Coat protein molecules engage in identical, equivalent interactions with one another, but not with the viral genome, to allow construction of a large, stable structure from a single protein subunit d. Coat protein molecules engage in identical, equivalent interactions with one another and with the viral genome to allow construction of a large, stable structure from different protein subunits

b. Coat protein molecules engage in identical, equivalent interactions with one another and with the viral genome to allow construction of a large, stable structure from a single protein subunit

Which of the following does not play a role in viral entry a. Clathrin-mediated endocytosis b. Diffusion of viral particles in the cytoplasm c. Microtubule-mediated transport d. Sialic acids

b. Diffusion of viral particles in the cytoplasm

The TCR receptor of CD8 lymphocytes (cytotoxic) recognize endogenous antigen peptides presented by MHCII molecules, while the TCR receptor of CD4 lymphocytes (helper) recognize exogenous antigen paptides presented by MHCI molecules. a. True b. False: CD8 - endogenous antigen peptides - MHCI, and CD4 - exogenous antigen peptides - MHCII c. False: CD8 - exogenous antigen peptides - MHCI, and CD4 - endogenous antigen peptides - MHCII d. False: CD8 - exogenous antigen peptides - MHCII, and CD4 - endogenous antigen peptides - MHCI

b. False: CD8 - endogenous antigen peptides - MHCI, and CD4 - exogenous antigen peptides - MHCII

Neuraminidase (NA) binds to sialic acid allowing influenza virus attachment and subsequent entry. a. True b. False: Hemagglutinin (HA) and not NA c. False: NA binds to sialic acid inside the cell d. False: NA binds to sialic acid in the nucleus

b. False: Hemagglutinin (HA) and not NA

Chemical bonds between subunits are generally covalent. a. True b. False: non-covalent c. False: subunits do not bind d. False: it is presently not known

b. False: non-covalent

dsDNA viruses always encode their own DNA polymerase. a. True b. False: some use the host cell DNA polymerase, for example Polyomaviridae and Papillomaviridae c. False: some use the host cell DNA polymerase, for example Poxviridae and Herpesviridae d. False: some use the host cell DNA polymerase, for example Retroviridae and Adenoviridae

b. False: some use the host cell DNA polymerase, for example Polyomaviridae and Papillomaviridae

HIV and influenza viruses enter the host cell through membrane fusion facilitated by membrane fusion proteins. a. True b. False: the influenza virus uses cell fusion to free the genome from the capsid and the endosome containing the viral particle - allowing the genome to enter the nucleus c. False: only the influenza virus uses membrane fusion to enter the host cell d. False: membrane fusion proteins do not exist

b. False: the influenza virus uses cell fusion to free the genome from the capsid and the endosome containing the viral particle - allowing the genome to enter the nucleus

The hepatitis B virus always integrates into the host cell genome a. True b. False: there is no integration c. False: only some regions of the genome d. False: only dsDNA made by RT

b. False: there is no integration

Which statement about viral budding is incorrect? a. The viral spike glycoprotein can drive budding b. No host proteins are involved in the budding process c. Lipids assist structural proteins to interact with the membrane d. Budding can occur from the nucleus, ER, Golgi and plasma membrane

b. No host proteins are involved in the budding process

Which statement about polyadenylation of DNA virus mRNAs is true? a. Always occurs in the cytoplasm b. Occurs after cleavage of pre-mRNA c. Poly-A is added at the 5' end of pre-mRNA d. Specified by a stretch of U residues in the template like RNA viruses

b. Occurs after cleavage of pre-mRNA

We carry many viruses at any given time. Which statement is correct? a. All viruses make us sick and can be lethal b. Our immune system can manage most viral infections c. Humans are usually infected with one virus at a time d. The press is usually correct in their human virology reporting

b. Our immune system can manage most viral infections

What is multiplicity of infection - MOI? a. Number of infectious particles each cell receives b. PFU/number of cells c. Number of defective viral particles d. How many times a virus generates more viruses inside the same cell

b. PFU/number of cells

Classical complement pathway activation requires: a. Enough number of viruses b. Pathogens bound to antibodies c. A small amount of c3b that is always present d. Lectins

b. Pathogens bound to antibodies

What is RdRp? a. RNA-directed DNA polymerase b. RNA-directed RNA polymerase c. DNA-directed DNA polymerase d. DNA-directed RNA polymerase

b. RNA-directed RNA polymerase

Areas where lymphocytes encounter antigens, become activated, undergo clonal expansion, and differentiate into effector cells, can be found in: a. Primary lymphoid organs b. Secondary lymphoid organs c. Lymph nodes only d. Thymus only

b. Secondary lymphoid organs

Which of the following describe virus symmetry and self assembly? a. The bonding contacts of subunits are usually covalent b. The bonding contacts of subunits are usually non-covalent c. Each subunit has different bonding contacts with its neighbors d. Self-assembly of viral particles never occurs

b. The bonding contacts of subunits are usually non-covalent

For viruses that do not form plaques, endpoint dilution assays are commonly performed. What is the end point? a. The concentration of virus that leads to 100% infected cells b. The concentration of virus that leads to 50% infected cells c. The concentration of virus that leads to 10% infected cells d. The concentration of virus that leads to plaque formation

b. The concentration of virus that leads to 50% infected cells

A rapid SARS-CoV-2 antibody test with a positive M band but negative G band means that: a. The infection was a long time ago since only IgMs are produced b. The infection is recent and B-cell class switch to IgG has not happened yet c. The infection is recent and B-cell class switch to IgG has already happened d. It is not possible to infer time of infection with M bands

b. The infection is recent and B-cell class switch to IgG has not happened yet

What is infectivity? a. The total number of viral particles b. The number of infectious viral particles c. The number of infected host cells d. The number of viral genomes

b. The number of infectious viral particles

Define incubation period of a virus. a. Time between infection and onset of disease b. Time between infection and onset of disease symptoms c. Time between infection and disease resolution d. Time the infected person is contagious

b. Time between infection and onset of disease symptoms

What is the first biosynthetic event that occurs in cells infected with dsDNA viruses? a. Membrane fusion b. Transcription c. Protein synthesis d. All of the above

b. Transcription

Upon encounter with a macrophage or a dendritic cell, a dsDNA virus might be recognized by which PRR? a. TLR b. cGAS c. RLR d. CLR

b. cGAS

PKR is an interferon-induced enzyme in response to (blank space), leading to phosphorylation of (blankc space) and inhibition of protein translation. a. GDP, eIF2alpha b. dsRNA, eIF2alpha c. ssRNA, eIF2B d. ssRNA, eIF2alpha

b. dsRNA, eIF2alpha

The remarkable retroviral strategy includes: a. + ss RNA to - ssDNA to mRNA and +ss RNA genome b. + ss RNA to dsDNA to -ssDNA to mRNA and +ss RNA genome c. + ss RNA to - ssDNA to dsDNA to mRNA and +ss RNA genome d. + ss RNA to - ssDNA to dsDNA to mRNA and -ss RNA genome

c. + ss RNA to - ssDNA to dsDNA to mRNA and +ss RNA genome

In two-hit kinetics, the number of plaques is directly proportional to the square of the concentration of the virus inoculated. In this case, how many infectious viral particles need to infect one host cell? a. 1 b. 1^2 c. 2 d. 2^2

c. 2

An icosahedral virus with T=4 has 1 structural subunit per icosahedron face, leading to a total of 60 protein subunits in the viral capsid. a. 2 structural subunits per icosahedron face, with 120 total subunits b. 3 structural subunits per icosahedron face, with 180 total subunits c. 4 structural subunits per icosahedron face, with 240 total subunits d. 5 structural subunits per icosahedron face, with 300 total subunits

c. 4 structural subunits per icosahedron face, with 240 total subunits

Why is mRNA placed at the center of the Baltimore scheme? a. Because all viral particles contain mRNA b. Because all viral genomes are mRNA c. Because mRNA must be made from all viral genomes d. Because only cellular mRNAs are used to make viral particles

c. Because mRNA must be made from all viral genomes

Which is a part of the poliovirus replication strategy? a. Production of subgenomic RNAs b. De novo (without primer) initiation of RNA synthesis c. Circularization of template for initiation of RNA synthesis d. All of the above

c. Circularization of template for initiation of RNA synthesis

Intrinsic defenses are always present. Which of the following are included? a. Antibodies b. T cells c. Epigenetic silencing d. Skin

c. Epigenetic silencing

Adenovirus VA RNA I prevents activation of PKR, thus preventing protein translation initiation a. True b. False: It induces activation of PKR, thus preventing protein translation initiation c. False: It prevents activation of PKR, thus leading to protein translation initiation d. False: PKR is not related to translation initiation

c. False: It prevents activation of PKR, thus leading to protein translation initiation

Humoral immunity after the first exposure to the pathogen is identical to humoral immunity after the second exposure to the pathogen. a. True b. False: IgGs are produced first in the primary response c. False: memory B-cells producing IgGs respond immediately after second exposure d. False: IgMs are only produced in the primary response

c. False: memory B-cells producing IgGs respond immediately after second exposure

Packaging signals in viral (blank space) interact with viral (blank space) during viral assembly. a. Lipids, proteins b. Proteins, subassemblies c. Genomes, proteins d. Proteins, genomes

c. Genomes, proteins

How do interferons (IFNs) limit viral replication? a. IFNs directly inhibit viral translation b. IFNs lyse viral particles c. IFNs induce ISGs d. IFNs damage cells

c. IFNs induce ISGs

Inhibition of host cell gene expression might be advantageous to viral infections because: a. It increases competition between cellular and viral mRNAs for protein translation machinery b. It increases DNA synthesis c. It reduced competition between cellular and viral mRNAs for protein translation machinery d. It increases glycolysis

c. It reduced competition between cellular and viral mRNAs for protein translation machinery

Viral genomes must be distinguished from cellular DNA or RNA when assembly takes place. How is that achieved? a. Complete degradation of host cell genetic material before packaging b. Isolation of viral genomes in specific cellular compartments c. Packaging signals in the viral genome d. Marking cellular DNA or RNA with unpackaging signals

c. Packaging signals in the viral genome

What is an icosahedron? a. Solid with 16 faces, each an equilateral triangle b. Solid with 24 faces, each an non-equilateral triangle c. Solid with 20 faces, each an equilateral triangle d. Solid with 8 faces, non of which is a triangle

c. Solid with 20 faces, each an equilateral triangle

Upon encounter with a macrophage or a dendritic cell, a dsRNA virus might be recognized by which PRR? a. TLR b. RLR c. TLR and RLR d. None of the above

c. TLR and RLR

The region of an antibody that binds to the antigen and determines specificity is made of: a. The constant regions of 2 light chains and 2 heavy chains b. The variable regions of 2 light chains c. The variable regions of 2 light chains and 2 heavy chains d. The whole antibody

c. The variable regions of 2 light chains and 2 heavy chains

When doing a plaque assay, what is the purpose of adding a semi-solid agar overlay on the monolayer of infected cells? a. To stabilize progeny viral particles b. To keep cells adherent to the plate during incubation c. To restrict viral diffusion after lysis of infected cells d. To ensure that cells remain susceptible and permissive

c. To restrict viral diffusion after lysis of infected cells

Viral entry (with a few exceptions) requires attachment to a cell surface receptor. The main cellular function of the receptor is: a. Allow viral entry b. Try to Kill the virus c. Unrelated to viral entry d. Recruit cells of the immune system

c. Unrelated to viral entry

Viral particles are metastable. What does that mean? a. Viral particles are always in a stable, which allows complete protection of the genome b. Viral particles are always unstable, allowing permanent genome replication c. Viral particles are stable outside the host cell, allowing genome protection, while unstable inside the host cell, allowing genome replication and mRNA production d. Viral particles have unbreakable bonds

c. Viral particles are stable outside the host cell, allowing genome protection, while unstable inside the host cell, allowing genome replication and mRNA production

How many types of genomes and capsids, respectively, can we find among viruses? a. 7; 2 b. 5; 5 c. 5; 7 d. 7; 3

d. 7; 3

Which statement about viral DNA synthesis is not correct? a. Large DNA viruses encode many proteins involved in DNA synthesis b. Small DNA viruses encode at least one protein required for DNA synthesis c. Viral DNA replication is usually delayed after infection because it requires the synthesis of at least one viral protein d. All DNA polymerases are primer-dependent

d. All DNA polymerases are primer-dependent

Hematopoietic stem cells in the bone marrow generate which immune cells? a. Macrophages and neutrophils of the innate immune system b. Natural killer cells of the innate immune system c. T and B lymphocytes of the adaptive immune system d. All of the above

d. All of the above

How are Adenovirus (non-enveloped viruses) genomes released? a. Endosome acidification partially degrades viral capsid proteins b. Endosome acidification allows translocation of viral proteins to the endosome membrane, which later lead to membrane disruption c. The partially degraded capsid travels to the nucleus using the cytoskeleton; it binds the nuclear envelope pore and releases the genome d. All of the above

d. All of the above

How does RT work? a. Primer can be DNA or RNA b. Template can be DNA or RNA c. dNTPs are incorporated but not rNTPs d. All of the above

d. All of the above

How might viral infection lead to increased levels of ATP? a. Stimulation of glucose uptake or increased of glycolysis b. Increased fatty acid oxidation c. Increased utilization of glutamine d. All of the above

d. All of the above

Identify all enveloped ss + RNA viruses with helical capsid. a. SARS-CoV b. MERS-CoV c. SARS-CoV-2 d. All of the above

d. All of the above

Individual B and T cells each have an individual specificity for a single antigen. a. When a B or T cell interacts with its specific antigen, it is selected and becomes activated b. Activation results in proliferation, producing a large number of clones c. Each clone is reactive against the antigen that initially stimulated the original lymphocyte d. All of the above

d. All of the above

Most of our cells do not divide or do so rarely. What is the implication for viral DNA synthesis? a. viruses do not replicate well in quiescent cells b. viruses must induce host replication proteins c. Early viral gene products induce host replication proteins d. All of the above

d. All of the above

Some naked viruses deliver their genome into the nucleus by: a. Binding to the nuclear pore complex via a special protein that allows genome exit or endosome acidification allows translocation of viral proteins to the endosome membrane, which later lead to membrane disruption b. The viral particle enters the nucleus c. A partially degraded capsid completely disassembles upon binding to the nuclear pore complex d. All of the above

d. All of the above

Viral receptors on the cell surface: a. Can bind directly to icosahedral capsid proteins, or to glycoproteins of enveloped viruses b. Can be carbohydrate or protein molecules c. Have cellular functions unrelated to viral attachment d. All of the above

d. All of the above

What are the criteria for the identification of cell surface viral receptors? a. Binding between receptor and virus b. An antibody specific to the receptor blocks viral infection c. Disruption of the receptor gene blocks viral infection d. All of the above

d. All of the above

What are the major consequences of sentinel cell activation by viral pathogens? a. Interferon production b. Inflammation c. Recruitment of the adaptive immune system d. All of the above

d. All of the above

What are the requirements for a successful viral infection? a. Enough number of viruses b. Cells accessible, susceptible and permissive c. Local antiviral immune defense absent or overcome d. All of the above

d. All of the above

Which of the following assist in viral dissemination in the infected animal? a. Viremia b. Basolateral release from epithelial cells and basement membrane inflammation c. Movement through the lymphatic system d. All of the above

d. All of the above

Which of the following is an example of a cytopathic effect? a. Cell death b. Syncytium formation c. Rounding up and detachment d. All of the above

d. All of the above

Why is SARS-CoV-2 vaccine protection mainly assessed by the quantification of neutralizing antibodies? Does this show the whole picture? a. Because assays for neutralizing antibodies are relatively easy to perform and are well established in general; it does not provide the whole picture since other antibodies, memory B cells, cellular immunity, and memory T cells are left out b. Because detecting memory cells is much harder to perform since they exist in much lower numbers, and they can be in the blood or in tissues; it does not provide the whole picture since other antibodies, memory B cells, cellular immunity, and memory T cells are left out c. Because assays to detect memory B and T cells are much harder to perform and are not generally implemented; it does not provide the whole picture since other antibodies, memory B cells, cellular immunity, and memory T cells are left out d. All of the above

d. All of the above

Why is the PI3K/mTOR pathway so often hijacked during viral infection? a. Because it leads to increased protein synthesis b. Because it leads to increased lipid synthesis c. Because it leads to increased nucleotide synthesis d. All of the above while inhibiting catabolic processes such as autophagy

d. All of the above while inhibiting catabolic processes such as autophagy

Which of the following are characteristics of icosahedral symmetry in viral capsids? a. Produces a solid with 20 faces, each an equilateral triangle b. Allows formation of a closed shell with 60 identical subunits c. Fivefold, threefold and twofold axes of symmetry d. All of the above, plus the T number describes the number of facets per icosahedral face

d. All of the above, plus the T number describes the number of facets per icosahedral face

What is a virus? a. An infectious cell that is an obligate intracellular parasite always made of nucleic acid (DNA or RNA genome) and protein (coat or capsid), sometimes with a lipid envelope b. An infectious particle that is an obligate intracellular parasite always made of nucleic acid (DNA or RNA genome) and lipid (coat or capsid), sometimes with a protein envelope c. An infectious particle always made of nucleic acid (DNA or RNA genome) and protein (coat or capsid), sometimes with a lipid envelope d. An infectious particle that is an obligate intracellular parasite always made of nucleic acid (DNA or RNA genome) and protein (coat or capsid), sometimes with a lipid envelope

d. An infectious particle that is an obligate intracellular parasite always made of nucleic acid (DNA or RNA genome) and protein (coat or capsid), sometimes with a lipid envelope

What are cytopathic effects? a. Cell death b. Inclusion bodies c. Rounding up and detachment d. Cellular changes induced by viral infection

d. Cellular changes induced by viral infection

The incubation period of SARS-CoV-2 can extend to 14 days. However, the median incubation time is 1-2 days (as established by the CDC). a. True b. False: 7-10 days c. False: 10-12 days d. False: 4-5 days

d. False: 4-5 days

IgG in a monomer, IgA is a pentamer and IgM is a dimer a. True b. False: IgA is a monomer c. False: IgA is a monomer and IgM is a pentamer d. False: IgA is a dimer and IgM is a pentamer

d. False: IgA is a dimer and IgM is a pentamer

Acquisition of an envelope always occurs after assembly of internal structures. a. True b. False: always before assembly of internal structures c. False: always at the same time of internal structure assembly d. False: after assembly of internal structures or simultaneously, depends on the type of enveloped virus

d. False: after assembly of internal structures or simultaneously, depends on the type of enveloped virus

ssDNA genomes always make dsDNA before producing mRNA, but that is not required for genome duplication a. True: for example, Parvoviridae b. False: it is not required to produce mRNA, only the viral genome c. False: they do not have to produce dsDNA all d. False: dsDNA is required for both mRNA production and viral genome duplication

d. False: dsDNA is required for both mRNA production and viral genome duplication

Viral particle cell entry is achieved by exocytosis or membrane fusion a. True b. False: exocytosis only c. False: endocytosis only d. False: endocytosis or membrane fusion

d. False: endocytosis or membrane fusion

Paramyxoviridae, Rhabdoviridae, Orthomyxoviridae and Filoviridae are non-enveloped ss + RNA viruses with helical capsid. a. True b. False: enveloped c. False: ss - RNA d. False: enveloped ss - RNA

d. False: enveloped ss - RNA

Antigen presentation can happen in gut-associated lymphoid tissues (GALTs) but not in mucosa-associated lymphoid tissues (MALT). a. True b. False: it can happen in MALTs but not in GALTs c. False: only in lymph nodes d. False: in both GALTs and MALTs

d. False: in both GALTs and MALTs

Viral assembly is not dependent on host cell machinery. a. True b. False: it requires DNA polymerase and chaperones c. False: it requires RNA polymerase, chaperones, and the secretory pathway d. False: it requires chaperones, transport systems, the secretory pathway, nuclear import/export machinery

d. False: it requires chaperones, transport systems, the secretory pathway, nuclear import/export machinery

ss + RNA viruses without a DNA intermediate must make mRNA a. True b. False: ss + RNA viruses without a DNA intermediate must make dsDNA c. False: ss + RNA viruses without a DNA intermediate must make - RNA to generate mRNA d. False: ss + RNA viruses without a DNA intermediate can use the + strand as mRNA

d. False: ss + RNA viruses without a DNA intermediate can use the + strand as mRNA

Hepadnaviridae carry RT in the virion a. True b. False: they use the host cell RT c. False: only Retroviridae have RT d. False: they encode RT

d. False: they encode RT

Non-cytopathic viruses induce very potent immune responses a. True b. False: they only induce inflammation c. False: they only induce apoptosis d. False: very weak immune responses due in part to lack of inflammation

d. False: very weak immune responses due in part to lack of inflammation

We use the light microscope to see viruses, while we use the electron microscope to see bacteria and human cells. a. True b. False: we normally use the electron microscope to observe all three (viruses, bacteria and human cells) c. False: we normally use the light microscope to observe all three (viruses, bacteria and human cells) d. False: we use the electron microscope to see viruses, while the light microscope can be used to see both bacteria and human cells

d. False: we use the electron microscope to see viruses, while the light microscope can be used to see both bacteria and human cells

Which statement about viral transmission is not correct? a. All virus infections are transmitted by shedding b. Speaking can produce an aerosol that can transmit infection c. Transmission is required to maintain a chain of infection d. Horizontal transmission is always within the same species regardless of generation

d. Horizontal transmission is always within the same species regardless of generation

Which of the following parameters is not affected by human intervention? a. Mortality rate b. Case fatality rate c. Reproductive index d. Incubation period

d. Incubation period

The cellular theory states that all living organisms are made of cells and that the cell is the basic unit of life. According to this perspective viruses are: a. Live organisms b. Live particles c. Live cells d. Infectious particles that become alive inside the host cell

d. Infectious particles that become alive inside the host cell

Some viral diseases do not behave as expected due to over-dispersion. What does that mean? a. It means that the number of new infections is linearly proportional to the number of already infected people b. It means that a large number of infected people are causing new infections c. It means that a small number of infected people are causing a small number of new infections d. It means that a small number of infected people are causing the vast majority of new infections

d. It means that a small number of infected people are causing the vast majority of new infections

Identify important examples of ss - RNA viruses with helical nucleocapsids. a. Herpes virus, varicella virus, papilloma virus, HIV, Epstein Barr virus b. Measles virus, herpes virus, HIV, rabies virus, ebola virus c. Varicella virus, papilloma virus, HIV, rabies virus, influenza virus d. Measles virus, mumps virus, influenza virus, rabies virus, ebola virus

d. Measles virus, mumps virus, influenza virus, rabies virus, ebola virus

Which of the following is an example of natural passive immunity? a. Vaccine against SARS-CoV-2 b. Antibodies against SARS-CoV-2 c. Getting infected by SARS-CoV-2 d. Mother IgGs against SARS-CoV-2 cross the placenta to fetus

d. Mother IgGs against SARS-CoV-2 cross the placenta to fetus

What is R0? a. Number of primary infections that can arise in a population of susceptible hosts b. Number of secondary infections that can arise in a population of non-susceptible hosts from a single infected individual c. Number of secondary infections that can arise in a population of susceptible hosts d. Number of secondary infections that can arise in a population of susceptible hosts from a single infected individual

d. Number of secondary infections that can arise in a population of susceptible hosts from a single infected individual

SARS-CoV-2 mRNA vaccines induce both humoral and cellular immunity. To determine vaccine protection we should: a. Quantify all IgM and IgG antibodies b. Quantify IgM and IgG neutralizing antibodies c. Quantify memory B and T cells d. Quantify IgM and IgG antibodies, as well as memory B and T cells

d. Quantify IgM and IgG antibodies, as well as memory B and T cells

What information is encoded in a viral genome? a. Replication of the viral genome, viral assembly with genome packaging, timing of the replication cycle, modulation of host defenses, complete protein synthesis machinery b. Replication of the viral genome, viral assembly with genome packaging, timing of the replication cycle, complete protein synthesis machinery, lipid membrane synthesis c. Replication of the viral genome, viral assembly with genome packaging, timing of the replication cycle, lipid membrane synthesis , spread to other cells and hosts d. Replication of the viral genome, viral assembly with genome packaging, timing of the replication cycle, modulation of host defenses, spread to other cells and hosts

d. Replication of the viral genome, viral assembly with genome packaging, timing of the replication cycle, modulation of host defenses, spread to other cells and hosts

ACE2, sialic acid and CD4 are receptors for which viruses, respectively? a. SARS-CoV-2, herpes simplex virus, HIV b. Poliovirus, mumps virus, SARS-CoV-2 c. HIV, influenza virus, SARS-CoV-2 d. SARS-CoV-2, influenza virus, HIV

d. SARS-CoV-2, influenza virus, HIV

The outer layer of which of the following is dead but can still serve as a portal of viral entry upon scratch or small cut? a. Respiratory tract b. Digestive tract c. Eye d. Skin

d. Skin

A cell that has a functional receptor for a given virus, and which supports viral genome replication can be defined as: a. Permissive and resistant b. Susceptible and resistant c. Resistant d. Susceptible and permissive

d. Susceptible and permissive

ssDNA viruses must complete what before starting transcription of mRNA? a. Nothing b. Addition of poly-A tail c. Addition of CAP d. Synthesis of dsDNA

d. Synthesis of dsDNA

Sentinel cells (macrophages and dendritic cells) of the innate immune system are present in all tissues and organ systems. How do viral pathogens activate sentinel cells? a. Through MHCI-antigen binding b. Through MHCII-antigen binding c. Through chemokine receptors d. Through PRRs

d. Through PRRs

Adenovirus E1A protein stimulating the expression of E2 protein, which then regulates expression of IVa2 and L4, is an example of: e. A negative auto-regulatory loop f. Repression of gene expression g. Cascade regulation h. All of the above

g. Cascade regulation