Ch 26
Viruses in Group VI of the Baltimore classification have single-stranded ________ as their genetic material and use _______ _________ to convert it into double-stranded DNA
RNA; reverse; transcription; DNA
What is the most common route of viral entry in human infections? Respiratory epithelia The surface of the eye The skin The urogenital epithelia
Respiratory epithelia
New combinations of the hemagglutinin (H) and neuraminidase (N) protein spikes arise in the influenza virus when the viral genomes are ________ during infection of a single cell by more than one influenza virus.
reassorted or recombined
Once inside a host, many viruses will only target a specific set of cells. This is known as _______ ______
tissue tropism
Along with their unusually large size, giant viruses challenge traditional assumptions about viruses because they can contain genes involved in the process of _________ such as aminoacyl-tRNA synthetases.
translation
What happens during antigenic shift in influenza viruses? Small changes in the HA and NA genes accumulate due to mutation. Major changes in the HA and NA genes occur due to mutation. Major changes in the HA and NA genes occur due to reassortment. Small changes in the HA and NA genes accumulate due to reassortment.
Major changes in the HA and NA genes occur due to reassortment.
What are the two most common routes of HIV transmission? Multiple select question. Sharing of needles among intravenous drug users Respiratory droplets (for example, sneezing) Intimate sexual contact Consumption of contaminated food or water Blood transfusion
Sharing of needles among intravenous drug users Intimate sexual contact
HPV can transform a normal cell into a cancerous cell because the viral protein E7 binds the cell protein _________ and the viral protein E6 binds the cellular protein _______. These cellular proteins control cell growth and division.
Rb, p53
The disease that causes the development of numerous small cavities in the brain of infected individuals due to death of neurons producing a spongy appearance is called acute viral encephalomyelitis. transmissible spongiform encephalopathy. Alzheimer's disease. Parkinson's disease.
transmissible spongiform encephalopathy.
________ is a condition characterized by viruses freely circulating in the blood or lymph.
Viremia
Viruses are unable to reproduce without which of the following? A host cell An envelope Another virus Reverse transcriptase
A host cell
Which of the following viruses uses the cellular machinery of a bacterium for its own replication? Retrovirus Prophage Lysogen Bacteriophage
Bacteriophage
The classification of viruses based on genome replication is known as the ________ classification after the scientist that first proposed it.
Baltimore
Why can't we treat HIV infections with a single drug? Inhibiting a single stage of the viral replication process is ineffective. Because if its high mutation rates, the virus quickly becomes resistant to any single drug. No single drug has been found that can prevent HIV from replicating in CD4+ cells.
Because if its high mutation rates, the virus quickly becomes resistant to any single drug.
Viral genomes may be composed of ____ or ____ and may be _____-stranded or ______-stranded.
DNA, RNA, single, double
Viruses that contain _____ as their genetic material are often assigned to species group; the same is not true of viruses with ______ as their genetic material.
DNA; RNA
Which two genes of the HPV are necessary to drive tumorigenesis? Multiple select question. p53 E6 Rb E7 E2F
E6 E7
Which of the following are symptoms associated with acute retroviral syndrome? Cancer Flu-like symptoms Susceptibility to opportunistic infections Diarrhea Joint pain
Flu-like symptoms Diarrhea Joint pain
Which of the following surface spikes proteins (enzymes) facilitates the binding of influenza viruses to the cell surface and allow it to gain access to the cell interior? Fusion protease Endocytosis protease Neuraminidase Hemagglutinin
Hemagglutinin
A virus whose capsid resembles a soccer ball, with 20 equilateral triangular facets is said to have a(n) ________ capsid.
Icosahedral
What is the basic capsid structure of most animal viruses? Icosahedral Threadlike Helical Rodlike
Icosahedral
The largest virus ever discovered is _______
Pithovirus
The first AIDS drug licensed for clinical use was AZT, a reverse transcriptase inhibitor. This class of drugs target which stage of HIV's life cycle? Replication Assembly Entry into CD4+ Cells Attachment
Replication
A _____ is the protein sheath that surrounds the nucleic acid core of a virus.
capsid
Which of the following diseases are transmissible spongiform encephalopathies (TSEs)? Multiple select question. ebola chronic wasting disease "mad cow" disease Creutzfeldt-Jakob disease scrapie severe acute respiratory syndrome
chronic wasting disease "mad cow" disease Creutzfeldt-Jakob disease scrapie
Because they are very resistant to _________ , prions are able to pass through the acidic digestive tract following ingestion of tainted food, without being degraded by proteases.
degradation
Genes in the viral genome expressed first are referred to as ______. late genes middle genes early genes expressed genes
early genes
Viral genes that are expressed first after the virus enters a host cell and uses its transcription and translation systems to produce viral proteins are known as ______ __________
early genes
A non toxin-producing Vibrio cholerae bacterium can be changed into potentially deadly toxin-producing bacterium if it is not expressing genes for pili but becomes infected by toxin-encoding phage expressing genes for pili and becomes infected by a toxin-encoding phage expressing genes for pili regardless of whether it has been infected by a phage
expressing genes for pili and becomes infected by a toxin-encoding phage
HIV enters a host T-helper cell by first binding to the CD4 receptor and a coreceptor such as CCR5, and then _____ with the cell membrane.
fusing
A viral reproductive cycle that includes the production of a prophage is the _______ cycle
lysogenic
A bacteriophage that integrates its own DNA into that of its host cell, allowing it to replicate with the host's genome is a(n) ________ phage.
lysogenic or temperate
Latency in HSV-1 and HSV-2 is controlled by a single viral ________ and several _______
mRNA; miRNAs
The reverse transcriptase enzyme of HIV is less accurate than other polymerases, which causes it to make errors relatively frequently. As a result, HIV has a high ______ rate.
mutation
A phage DNA segment that is integrated into a host bacterial cell's genome during the lysogenic cycle is known as a(n) ________
prophage
A disease that was prominent in the past, and whose incidence suddenly increases after a period of low incidence, is called a _________ disease.
re-emerging
Prion proteins enter the body typically through the skin. the airways. mucous membranes. the digestive system.
the digestive system.
When outside of a host cell, an individual viral particle is known as a(n) ___
virion
Of the following list, choose all that may be found in a viral particle. A protein shell DNA An envelope A small rough ER RNA A nucleus
A protein shell DNA An envelope RNA
E. coli-infecting bacteriophages can exhibit which of the following structures? An icosahedral head with a short tail A helical head with a long tail and complex base plate A bottle-shaped structure with no tail An icosahedral head with two long tails An icosahedral head with a long tail and complex base plate
An icosahedral head with a short tail An icosahedral head with a long tail and complex base plate
What are the two features used by the CDC to diagnose AIDS? At least one of the HIV-associated diseases or syndromes Antibody count above 105/ml T-cell count in the blood below 200/ml No T-helper cells in the blood plasma
At least one of the HIV-associated diseases or syndromes T-cell count in the blood below 200/ml
What is the term that describes the switch from a lysogenic prophage to a lytic cycle? Reversal Induction Activation Adsorption Expression
Induction
Lambda phage and most temperate phages can enter the lytic cycle by derepressing their prophage at which of the following times? When the host cell is killed When the repressor protein binds to its target operator When the host cell is stressed When the level of lambda repressor protein increases
When the host cell is stressed
Two proteins comprise the surface spikes of the influenza virus; _________ (HA, or H spike), which aids the virus in gaining access to the cell interior and (NA, or N spike), which helps the daughter viruses break free of the host cell once virus replication has been completed.
hemagglutinin; neuraminidase
Viral genes that generally code for proteins important in assembly and release of viral particles from a host cell are called ______ genes.
late
_____________ involves isolating DNA from an environmental sample, sequencing it, and comparing it to known sequences in DNA databases.
metagenomics
In order for a toxin-encoding phage to infect V. cholerae, the bacterium must possess a cell wall. flagella. pili. membrane glycoprotein.
pili.
Choose the molecules that control latency in HSV-1 and HSV-2. Multiple select question. A single viral mRNA Several tRNAs Several microRNAs A single cellular mRNA
A single viral mRNA Several microRNAs
Viroids are infectious disease agents in plants that are composed solely of circular ____________
DNA
Virtually all viruses that have been implicated in human cancer use _________ their nucleic acid at some point during their replicative cycle.
DNA
Choose the Baltimore groups that contain viruses which use reverse transcription. Group VI Group V Group III Group VII Group IV
Group VI Group VII
What are the two main ways in which a virus can spread to infect secondary sites in the human body? Multiple select question. In blood or lymph Via muscle tissue Via neurological tissue Via the skin
In blood or lymph Via neurological tissue
After the initial acute disease (painful blisters) subsides due to an immune response, where can HSV-1 and HSV-2 be found? In the nuclei of bone making cells located in the vertebral column In the nuclei of motor neurons around the body In the nuclei of white blood cells In the nuclei of sensory neurons that innervate the site of infection
In the nuclei of sensory neurons that innervate the site of infection
What is the consequence of the destruction of CD4+ cells by HIV to the human body? Growth of helper T cells are no longer regulated, eventually causing cancer. The virions and CD4+ cell components block veins and arteries, leading to vascular disease. It is no longer defended against invading bacteria and viruses, leading to opportunistic infections. The virions and CD4+ cell components block the lymph nodes, leading to infection. Oxygen cannot be transported throughout the body from the lungs.
It is no longer defended against invading bacteria and viruses, leading to opportunistic infections.
Which of the following denotes the misfolded version of the normal prion protein? PrPPR PrPC PrPSc PrPTSE
PrPSc
How do viroids replicate in plants? They replicate using a helper virus that must co0nfect the host. They are replicated by a host RNA polymerase and have catalytic activities. They are replicated by a reverse transcriptase and the host RNA polymerase.
They are replicated by a host RNA polymerase and have catalytic activities.
How do viroids cause disease in a plant? They kill chloroplasts. They encode nucleases that destroy the host cell nucleic acids. They produce siRNAs that can cause mild to severe disease in the host plant. They lyse cells as they spread through the host.
They produce siRNAs that can cause mild to severe disease in the host plant.
Choose the features that are common to viruses involved in human cancer. Multiple select question. They are all naked. Virtually all of them use DNA as their genetic material at some point in their replicative cycle. They all possess a mechanism that ensures their genome is stably inherited during cell division. They all establish long persistent infections in the human body. They all use reverse transcription at some point during their replicative cycle.
Virtually all of them use DNA as their genetic material at some point in their replicative cycle. They all possess a mechanism that ensures their genome is stably inherited during cell division. They all establish long persistent infections in the human body.
Attachment of HIV occurs when the ________ glycoprotein binds to the _______ receptor on the surface of an immune system macrophage or T cell.
gp120, cd4
A viral capsid with an overall _______ structure has a rodlike or threadlike appearance.
helical
Most viruses have a capsid that is ___ or ________ in terms of its basic structure and symmetry.
helical; icosahedral
After the immune system can no longer control HIV, it starts killing cells expressing the CD4 antigen. Of those cells, the most important types are the T-______ cells which coordinate the immune response and the ______ which engulf pathogenic bacteria.
helper macrophages
The basic capsid shape of most animal viruses is a(n) ______
icosahedron
In order to study viruses in the environment, scientists isolate nucleic acids from an environmental sample, sequence them, and use computers to assemble genomes and compare them to known sequences in databases. This approach is known as _______
metagenomics
Infectious proteins that can cause transmissible spongiform encephalopathies are called _______
prions
In ________ viral infections, a virus or its genome can be found in the host for long periods of time: years, decades, and sometime for the rest of the host's life.
persistent
Some studies suggest that there is more genetic variation in the viruses of an HIV-infected patient than in all influenza viruses worldwide. This, and difficulties in vaccine development may be attributed to permanent changes in viral gene expression when the viral genome is integrated into that of the host cell. changes in gene expression caused by segments of the host cell's DNA being transcribed and translated along with the viral genome. its high propensity for recombination with other strains that infect the same cell. the inability of reverse transcriptase to proofread, which results in a high mutation rate.
the inability of reverse transcriptase to proofread, which results in a high mutation rate.
In the Baltimore classification of viruses, there are _________ groups of viruses and every known virus can be placed in only one such group based on the way it __________ its genome.
7 or seven; replicates
Which of the following best describes how a phage undergoes the lytic cycle? Attachment; integration; synthesis; assembly; repression; replication Attachment; penetration; integration; repression; replication Attachment; penetration; synthesis; assembly; release Attachment; synthesis; assembly; penetration; release
Attachment; penetration; synthesis; assembly; release
Why is it difficult to classify influenza viruses based on their host? Because there are four types of influenza viruses that can infect many different hosts (humans, birds, pigs, dogs, cats) Because some influenza viruses do not appear to cause disease in humans. Because different influenza viruses infect different tissues in different hosts.
Because there are four types of influenza viruses that can infect many different hosts (humans, birds, pigs, dogs, cats)
Viruses placed in Group I and II of the Baltimore classification have single or double-stranded _______ as their genetic material
DNA
Which of the following statements is true regarding vaccination for influenza? Only one vaccine is required to protect against all subtypes of the virus. Different vaccines are required to protect against the three major types of the virus, but not subtypes. Different vaccines are required to protect against the many different subtypes of the virus.
Different vaccines are required to protect against the many different subtypes of the virus.
The time between adsorption and the formation of new viral particles is called which of the following? Release period Eclipse period Lytic period Lysogenic period
Eclipse period
Which statement accurately compares the morphological diversity of naked and enveloped vir uses? Naked viruses exhibit much greater morphological diversity than enveloped viruses. Enveloped viruses and naked viruses exhibit similar morphological diversity. Enveloped viruses exhibit much greater morphological diversity than naked viruses.
Enveloped viruses exhibit much greater morphological diversity than naked viruses.
Bacteriophage that infect the bacterial species________ _____ were among the first to be discovered and are thus some of the best studied.
Escherichia coli
Choose all the conventional systematic groups that are also used to classify viruses. Domain Kingdom Family Order Genus Class
Family Order Genus
Which of the following is an example of a retrovirus? Poliovirus Tobacco mosaic virus Influenza HIV Herpes simplex
HIV
Which of the following describes induction as the process of switching from a lysogenic prophage to a lytic cycle It requires turning on the gene expression necessary for capsid formation. It requires turning on the gene expression necessary for helical tail formation. It requires repression of the gene expression necessary for the lysogenic cycle. It requires turning on the gene expression necessary for the lytic cycle.
It requires turning on the gene expression necessary for the lytic cycle.
The viral envelope is composed of which of the following (choose all that apply)? Multiple select question. Nucleic acids Lipids Glycoproteins Proteins Sugars
Lipids Glycoproteins Proteins
Which of the following is not found in the viral envelope? Proteins Lipids Glycoproteins Nucleic acids
Nucleic acids
During lysogenic cycle, the integrated viral DNA segment within the host's genome is called which of the following? Vector Prion Viroid Prophage
Prophage
Which of the following are true of influenza viruses? Protein spikes on the capsid surface are made up of hemagglutinin and neuraminidase. They are naked viruses. They all have the same capsid protein. Their genome is composed of segmented RNA.
Protein spikes on the capsid surface are made up of hemagglutinin and neuraminidase. Their genome is composed of segmented RNA.
Why do RNA viruses appear to have higher rates of mutation? RNA nucleotides are more unstable than DNA nucleotides. RNA replication is error-prone. RNA viruses can incorporate a variety of nonstandard bases. RNA viruses replicate faster.
RNA replication is error-prone.
Viruses are nonliving particles with a genome made of DNA or ___, surrounded by a shell (capsid) made of ____
RNA, proteins
Which of the following statements All viruses carry at least one type of enzyme, their polymerase. With the exception of the capsid and the envelope, viruses do not carry any additional proteins or enzymes. Some viruses carry specific enzymes needed during the early stage of replication.
Some viruses carry specific enzymes needed during the early stage of replication.
Which of the following phages are icosahedral and have short tails? T2, and T4 T2, and T6 T4, and T6 T3 and T7
T3 and T7
How does infection by the CTXΦ phage result in a disease causing cholera strain? The phage carries two genes that encode the proteins necessary to make the cholera toxin. The phage can insert itself in front of the bacterial operon that encode the cholera toxin. This results in overexpression of the toxin. The phage carries one of the two genes necessary to make the cholera toxin. The other gene is found in the bacterial chromosome.
The phage carries two genes that encode the proteins necessary to make the cholera toxin.
In phage λ, initiation of the lysogenic or lytic cycle is determined in what way? The regulatory protein that binds to phage DNA determines whether genes for replication or integration are expressed. During replication, both lytic and lysogenic phages are produced, so the cycle is determined by what type of phage infects the host cell. Phage generations alternate, so if the last generation was lysogenic, the following generation will be lytic, and vice versa.
The regulatory protein that binds to phage DNA determines whether genes for replication or integration are expressed.
Which of the following are reasons why classifying viruses by disease they cause can be impractical? Some viruses have a very narrow host range. The same disease can be caused by many different viruses. Some viruses can cause different disease in different context. Some viruses can only infect certain types of cells. Some viruses do not appear to cause any disease.
The same disease can be caused by many different viruses. Some viruses can cause different disease in different context. Some viruses do not appear to cause any disease.
Which feature of influenza viruses is the reason why vaccines against them have to be produced each year? The viruses have an RNA genome and immune response against RNA molecules is generally weak. The viruses exhibit low levels of mutation. The viruses exhibit high levels of mutation. It is difficult to purify proteins from influenza viruses and the presence of impurities results in a short-lived immune response.
The viruses exhibit high levels of mutation.
Of the following, which are characteristics of RNA viruses? . Replication is relatively accurate, so mutation rates are low. They only infect eukaryotic cells. They can contain a single stranded or a double-stranded RNA genome. Most contain a circular single-stranded RNA genome. They require a viral encoded polymerase.
They can contain a single stranded or a double-stranded RNA genome. They require a viral encoded polymerase.
Which of the following is a virus that has a helical capsid? Tobacco mosaic virus Influenza virus Poliovirus Bacteriophage T4
Tobacco mosaic virus
Identify the disease agent that ranges in size from about 20-250 nm in diameter. Bacterium Virus Prions
Virus
Which of the following statements most accurately describes the host specificity of viruses? Viruses infect all types of organisms, but individual viruses are very limited in the species and cell types they can infect. Viruses only infect bacteria and animals, and individual viruses are very limited in the species and cell types they can infect. Viruses infect all types of organisms, and individual viruses can infect all species and cell types. Viruses infect only bacteria and animals, but individual viruses can infect all species and cell types.
Viruses infect all types of organisms, but individual viruses are very limited in the species and cell types they can infect.
How can a benign strain of the cholera bacterium become disease-causing? When it is infected by a virus that carries the genes for the cholera toxin When it is infected by a phage that carries genes for the cholera toxin AND genes for the production of pili When it is infected by a virus that carries genes for the production of pili
When it is infected by a virus that carries the genes for the cholera toxin
A(n) _______ infection involves the rapid replication of the virus, often at the site of infection, which leads to sudden symptom onset.
acute
THe T4 bacteriophage has a "head" shaped as an elongated icosahedron and a "tail" that exhibits helical symmetry. This is a complex virus that exhibits ________ , or twofold, symmetry.
binal
A complex virus that is neither entirely icosahedral not entirely helical (for example, the T4 phage) is said to have binal symmetry. icosahelical symmetry. dimorphic symmetry.
binal symmetry.
The genetic material of viruses classified into Group III of the Baltimore classification is _________-stranded _______
double RNA
Small changes to the HA and NA genes of influenza viruses due to mutation are known as antigenic ______
drift
The ________ period occurs between the attachment and assembly stages in the bacteriophage reproductive cycle because cell lysis during that time will prevent the release of active virions.
eclipse
When they enter the cell, viruses in Group II of the Baltimore classification have to convert their single-stranded RNA into double-stranded RNA. have to convert their double-stranded DNA into single-stranded DNA. have to convert their single-stranded RNA into double-stranded DNA. have to convert their single-stranded DNA into double-stranded DNA.
have to convert their single-stranded DNA into double-stranded DNA.
Viruses can infect all types of organism that have been investigated for their presence, but each type of virus has a relatively narrow ______ _______
host range
The damage to tissues during an infection with the influenza virus is usually due to the _______ response of the host
inflammatory
Bacteriophage exhibit two reproductive cycles: the _______ cycle, in which the latent phage is replicated with the host cell, and the ________ cycle, in which phage undergo replication within the host cell, eventually causing it to rupture.
lysogenic lytic
When tightly associated, the genome and the surrounding protein shell of a virus are collectively known as the ________
nucleocapsid
Viruses are facultative extracellular parasites obligate extracellular parasites facultative intracellular parasites obligate intracellular parasites
obligate intracellular parasites
A single-stranded RNA virus with a genome that can serve as the mRNA to produce viral proteins is a _______-strand virus; however, if the genome is complimentary to the viral mRNA, it is a ________-strand virus.
positive; negative
Virions lack the enzymes necessary for the synthesis of ______ , as well as most of the enzymes necessary for the replication of ________ acids.
proteins; nucleic
A virus that possesses an RNA genome that is reverse-transcribed into DNA using reverse transcriptase is known as a(n) _________
retrovirus
HIV particles that infect human host cells carry a viral enzyme called _____ ________which is needed by the virus to make DNA from RNA.
reverse transcriptase
When is the genome of HIV transcribed and translated to produce new RNA genomes, as well as proteins necessary for the assembly of new virions? After the viral RNA has been copied into DNA and has integrated into a host chromosome Just before the virus exits the cell, after immature virus particles have formed at the cell membrane Immediately after the virus gains entry into the cell
After the viral RNA has been copied into DNA and has integrated into a host chromosome
What stages of the HIV life cycle have been targeted by therapeutic drugs? Attachment Genome integration Viral entry Release of virions from the host cell Genome replication Maturation of viral proteins
Attachment Genome integration Viral entry Genome replication Maturation of viral proteins
The viral reproductive cycle that occurs when viral DNA is incorporated into and replicated with the infected host cell's genome is known as which of the following? Lytic cycle Integration cycle Induction cycle Lysogenic cycle
Lysogenic cycle
Of the following diseases, which is not a transmissible spongiform encephalopathy (TSEs)? Severe acute respiratory syndrome (SARS) Creutzfeldt-Jakob disease (CJD) Scrapie Mad cow disease
Severe acute respiratory syndrome (SARS)
Which of the following is a receptor for HIV virions? CD8 antigen MHC class I glycoprotein MHC class II glycoprotein CD4 antigen
CD4 antigen
How does HIV infect a CD4+ cell after binding to the CD4 receptor? It is engulfed by the cell and the capsid is digested by cellular enzymes, freeing the viral genome and enzymes in the cytoplasm. It binds to a coreceptor, and fuses with the cell membrane. An injection tube pierces the cell membrane and injects the genome into the host cell's cytoplasm. It secretes enzymes that break down the cell membrane, creating an entry pore for viral contents to pass through.
It binds to a coreceptor, and fuses with the cell membrane.
What is the effect of the initial acute disease episode after infection with an HSV-1 or HSV-2? Formation of painful blisters all over the body surface A rash similar to that caused by chicken pox Flu-like symptoms, such as fever, nausea, headache Formation of painful blisters at the site of infection
Formation of painful blisters at the site of infection
An HIV virion acquires its envelope by associating with a portion of the plasma membrane containing HIV spike glycoproteins. The membrane enfolds the viral capsid and then what happens? It buds from the surface of the cell. It shrinks from the surface of the cell. It dissolves from the surface of the cell.
It buds from the surface of the cell.
What are the two subtypes of HPV that are most commonly implicated in cervical cancer? HPV 16 and HPV 18 HPV 6 and HPV 8 HPV 11 and HPV 23 HPV 1 and HPV 2
HPV 16 and HPV 18
How do viruses replicate? Inside the host cell, the genome is replicated using viral DNA polymerase, after which the capsids undergo binary fission. Inside a host cell, the genome is replicated using viral DNA polymerase and capsid proteins are synthesized using viral enzymes. Genetic material is exchanged among two virions, undergoes recombination, and is packaged in capsids synthesized by the parents. Host cells' transcription and translation systems are used to replicate the genome and create capsid proteins.
Host cells' transcription and translation systems are used to replicate the genome and create capsid proteins.
Which of the following may take place during bacteriophage reproduction after the phage genome is injected into the host cell? Multiple select question. Reverse transcriptase reverse-transcribes DNA from viral RNA for integration. Lysogenic phage becomes lytic when cell stress causes depression of the prophage. New virus particles are synthesized by the cell and then released by lysis or budding. Viral proteins are synthesized that act as templates to cause misfolding in those produced by the host cell. The viral DNA is integrated into the genome of the host cell, allowing it to replicate when the host cell divides.
Lysogenic phage becomes lytic when cell stress causes depression of the prophage. New virus particles are synthesized by the cell and then released by lysis or budding. The viral DNA is integrated into the genome of the host cell, allowing it to replicate when the host cell divides.
Which of the following infectious disease agents are composed solely of protein? Prions Viroids Viruses
Prions
Of the following list, which are the two most important types of cells killed by HIV? T-helper cells Macrophages B cells T-killer cells
T-helper cells Macrophages
Place the steps of the HIV life cycle in order with the step following the introduction of the virus into the human bloodstream at the top.
The HIV gp120 glycoprotein attaches to the CD4 receptor of a CD4+ cell and one of two coreceptors. Viral contents enter a CD4+ cell by endocytosis. Reverse transcriptase synthesizes a double strand of DNA that is complimentary to the viral RNA. Genetic material from the virus enters the nucleus and in incorporated into the host genome by a viral enzyme. Following a variable period of dormancy, the host cell machinery is directed to produce many copies of the virus. Virus particles leave the host cell by budding.
Which infectious agents are composed solely of RNA? Viroids Prions Episomes Viruses
Viroids
When is a lysogenic phage, such as lambda, likely to exit the lysogenic state and enter a lytic cycle? When the host cell is stressed When there is an overabundance of nutrients in the environment After the host cell dies
When the host cell is stressed
Which of the following describes a viral capsid? A portion of DNA that is inserted into the host genome The nucleic acid core of a virus The protein sheath that surrounds the nucleic acid core The base of a virus that attaches to the host cell An envelope rich in proteins and lipids that surrounds the protein sheath
The protein sheath that surrounds the nucleic acid core
Which of the following is the most effective form of AIDS treatment, even though it does not completely eliminate the virus from the patient's body? HIV vaccination The use of drugs that prevent the virus from entering a host cell The use of a combination of drugs that target different stages of the HIV life cycle The use of drugs that target reverse transcriptase The use of drugs that target a protease necessary for viral replication and assembly
The use of a combination of drugs that target different stages of the HIV life cycle
HIV is usually controlled effectively by the immune system for the first several years following infection, but eventually causes AIDS when which of the following occurs? Multiple select question. Two viral subtypes infect the same cell, leading to genetic recombination. The viral genome becomes integrated within the DNA of macrophages and CD4+ T cells. The viral load increases. The immune response fails in its continued response to the virus. Viral particles are manufactured by the host cell.
The viral load increases. The immune response fails in its continued response to the virus.
When phage λ infects a cell, the lysis or lysogeny "decision" depends on the expression and synthesis of which of the following? A regulatory protein that randomly binds to one of two promoters in the phage's DNA. Two regulatory proteins that compete for binding to sites on the phage's DNA. Two regulatory proteins that compete for binding to sites on the host's DNA.
Two regulatory proteins that compete for binding to sites on the phage's DNA.
HSV-1 and HSV-2 can be reactivated when the host is exposed to ______ light.
UV or ultraviolet
A virus with single-stranded RNA which is negative sense is in group ________ of the Baltimore classification
V
What type of cells are targeted and ultimately destroyed by HIV? Hepatocytes Neurons B cells CD4+ cells Erythrocytes
CD4+ cells
Choose the three types of persistent human viral infections based on the amount of virus present and when it is produced. . Acute Chronic Latent Slow Lysogenic
Chronic Latent Slow
Choose all factors that can trigger HSV-1 and HSV-2 reactivation in a human host. Multiple select question. Dehydration Immune suppression Exposure to UV light Exposure to extreme temperatures Hormonal changes Starvation
Immune suppression Exposure to UV light Hormonal changes
How does HIV compromise the human immune system, allowing opportunistic infections to invade the body? Infected CD4+ cells are killed until few are left. All CD4+ cells are mobilized to destroy the large number of HIV particles that are produced. HIV DNA that is incorporated into the CD4+ cell's genome induces those cells to attack and destroy the rest of the immune system cells. The large amount of energy required to repair cells lysed by HIV reduces the number of CD4+ cells that can be produced.
Infected CD4+ cells are killed until few are left.
What was different about the 2014-2015 Ebola outbreak compared to previous outbreaks? It caused severe hemorrhagic fever rather than pneumonia. It spread very rapidly to become pandemic. The strain of the virus mutated quickly, making vaccination ineffective. The virus was transmitted to humans through their close proximity to deer mice.
It spread very rapidly to become pandemic.
The DNA segment that is integrated into a bacterial host cell's genome is called a prophage, and the resulting cell is called which of the following? Temperate cell Lysogen Prophage
Lysogen
Which of the following are characteristics of DNA viruses? Multiple select question. Most contain double-stranded DNA. Some are retroviruses. Genome replication typically occurs in the nucleus of an infected host cell. They are typically classified as positive-strand or negative-strand viruses.
Most contain double-stranded DNA. Genome replication typically occurs in the nucleus of an infected host cell.
Viroids are tiny molecules of circular _____ that are important infectious agents of _____ .
RNA; plants
Viruses are unable to reproduce outside a host cell for which of the following reasons? They possess the enzymes necessary for protein synthesis and nucleic acid replication, but lack ribosomes. They possess ribosomes, but lack the enzymes necessary for protein synthesis and nucleic acid replication. They lack ribosomes and the enzymes necessary for protein synthesis and nucleic acid replication.
They lack ribosomes and the enzymes necessary for protein synthesis and nucleic acid replication.
How do viruses such as Mimivirus that are larger than 500 nm in diameter challenge traditional distinctions between viruses and obligate intracellular parasitic bacteria? Multiple select question. They undergo replication in the nucleus. They may be mistaken to be cells due to their unusually large size. They encode none of the proteins necessary for DNA replication. They possess genes involved in the translation process.
They may be mistaken to be cells due to their unusually large size. They possess genes involved in the translation process.
Bacteriophage contribute DNA to their hosts during the ______ cycle, which may allow phage genes to be expressed with those of the host.
lysogenic
HIV is transmitted when contaminated bodily fluids come into contact with a __________ ________ , or directly enter tissues.
mucous membrane
In latent infections, virions are only produced during intermittent episodes. continually budding off at a very low rate. constantly produced inside the host without exiting.
only produced during intermittent episodes.
Transmissible spongiform encephalopathies (TSEs) cause pneumonia through infection of the respiratory system. death of brain cells within large regions of the brain as a result of loss of blood flow. the expression of oncogenes in brain cells, leading to uncontrolled replication and tumor growth. the development of numerous small cavities in the brain as neurons die. a buildup of fluid in the brain, leading to memory loss.
the development of numerous small cavities in the brain as neurons die.
Prion diseases arise from the ability of the prion protein to multiply rapidly within the host, disrupting normal organ function. induce abnormal folding in normal proteins. cause host cells to lyse. cause deleterious mutations in the host cell genome.
induce abnormal folding in normal proteins.
In order for HIV to replicate in a white blood cell, it must ________ its double-stranded DNA into a random host chromosome.
integrate
Phage conversion is the switch from the lysogenic to the lytic cycle in an infected cell. the change in the structure of a bacteriophage that occurs when it comes into contact with a host cell. the change in the phenotype of a lysogenic bacterium caused by the prophage. the process in which the viral genome is expressed to produce new viral particles in an infected host cell.
the change in the phenotype of a lysogenic bacterium caused by the prophage.
The genome of HIV consists of two double-stranded RNA molecules. a single double-stranded DNA molecule. two single-stranded, positive-sense DNA molecules. two single-stranded, plus-sense RNA molecules.
two single-stranded, plus-sense RNA molecules.
What is the main reason for tissue damage during an infection with the influenza virus? Inflammatory response of the host Viral replication that kills hose cells Acidification of the extracellular space Release of toxins produced by viral infected cells
Inflammatory response of the host
Which of the following are mechanisms of transmission for transmissible spongiform encephalopathies (TSEs)? Multiple select question. Inhalation of prion-laden aerosols Ingestion of infected food Contact with feces and urine of an infected animal Transplantation of infected non-brain tissue into the body of a recipient Injection of infected brain tissue into the brain of a recipient
Ingestion of infected food Transplantation of infected non-brain tissue into the body of a recipient Injection of infected brain tissue into the brain of a recipient
What types of drugs aim to suppress the proliferation of HIV in the body by preventing the viral genome from being incorporated with the host cell's DNA? Reverse transcriptase inhibitors Integrase inhibitors Protease inhibitors Coreceptor blockers Fusion inhibitors
Integrase inhibitors
Which of the following describe the human skin as a point of entry for viruses? It serves as a barrier to infection because it has multiple layers and is slightly acidic. Viruses can enter through skin breaks caused by injury, insect bites, etc. It is the most common route of viral entry in the human body. It is the largest (in term of area) entry point for viruses
It serves as a barrier to infection because it has multiple layers and is slightly acidic. Viruses can enter through skin breaks caused by injury, insect bites, etc.
What type of drugs are used to suppress HIV replication by inhibiting the enzyme used to synthesize DNA using viral RNA? Viral integrase inhibitors Protease inhibitors Coreceptor blockers and fusion inhibitors Reverse transcriptase inhibitors
Reverse transcriptase inhibitors
Which of the following statements describe the genome and envelopment state of the influenza virus? Influenza virus has a segmented RNA genome and is enveloped. Influenza virus has a segmented RNA genome and is not enveloped. Influenza virus contains a single double stranded RNA molecule and is enveloped. Influenza virus has a segmented DNA genome and is enveloped.
Influenza virus has a segmented RNA genome and is enveloped.
Regarding bacteriophage, during which type of cycle does the phage enter a latent phase, allowing it to be replicated with the host cell? Virulent Lysogenic Non-lytic Lytic
Lysogenic
During which of the following reproductive cycles does a bacteriophage integrate its own DNA into the host cell's genome? Prophage cycle Lysogenic cycle Lytic cycle Virulent cycle
Lysogenic cycle
Late genes are those that code for proteins responsible for attachment of a virion to a host cell. the production of the initial viral proteins immediately following the entry of a virus into a host cell. replication of viral nucleic acid and production of the capsid. virus assembly and release of viral particles from a host cell.
virus assembly and release of viral particles from a host cell.
