Micro CH 6
Which of the following is (are) used to classify viruses? To be marked correct, you'll need to select all applicable statements, as there may be more than one correct answer.
**Type of nucleic acid present **Capsid symmetry
What information would be needed about this new virus in order to classify it into a viral family?
**Type of nucleic acid present **Capsid symmetry **Presence of an envelope **Genome architecture add note The International Committee on Taxonomy of Viruses (ICTV) classifies viruses based on four criteria: (1) type of nucleic acid present (DNA or RNA); (2) capsid symmetry (helical, icosahedral or complex); (3) presence or absence of an envelope; and (4) Genome architecture (ssDNA, ssRNA, etc.).
Which of the following are ways that viruses differ from prokaryotes and eukaryotes? To be marked correct, you'll need to select all true statements, as there may be more than one correct answer.
**Unlike prokaryotes and eukaryotes, viruses are classified as acellular particles. **Unlike prokaryotes and eukaryotes, viruses are not considered alive. **Unlike prokaryotes and eukaryotes, viruses are incapable of replicating independently from a host cell.
How could the researchers isolate and grow a particular virus from Jimena's blood
*The viruses can be cultivated using HeLa tissue culture. *The viruses can be injected into a fertilized chicken egg. *The viruses can be injected into a live animal host such as a mouse. add notes *** Viruses require a host for cultivation. Viruses may be grown using either cell cultures (the most common method of cultivation), live animal hosts or fertilized egg
In what year did Stanley Prusiner discover prions?
1982
Place the following events in the correct order as they occur in the lytic cycle: Assembly Penetration Release Replication Attachment
5, 2, 4, 1, 3
Which of the following is another term for a virus attaching to the host cell? TemperateLysisAbsorptionAdsorption
Adsorption
In the Spring of 2009, a novel H1N1 virus emerged that had a new combination of genes from pigs, humans, and birds. As a result, the virus spread quickly, resulting in a swine flu pandemic. Which of the following concepts explains why the outbreak occurred?
Antigenic shift
In which stage does formation of mature viruses occur?
Assembly
The host DNA is usually degraded during which stage?
Biosynthesis
An elderly patient who contracted chickenpox as a child now has shingles as an adult. You explain to your patient that both diseases are caused by the same virus, which lays dormant in the body prior to reactivation. Based on this information, choose the true statement.
During dormant periods, the virus exists episomally inside of infected host cells.
Which of the following events might trigger induction of a temperate bacteriophage?
Exposure to UV light
Miley's treatment plan included reducing the dose of her immuno-suppressive drugs. Why did this help her overcome the cancer? (NCLEX style) View Available Hint(s)
It allowed her immune system to become more active and kill the cancer cells. add notes Our immune system kills about 10,000 cancer cells every day. If we suppress that activity with drugs, there is a greater chance that one of these cells will slip through the cracks and cause disease.
What is the fate of the prophage during the lysogenic stage
It is copied every time the host DNA replicates.
Which of the following accurately describe Epstein-Barr virus? Select all that apply. (NCLEX style)
Latent Oncogenic Persistent
Which enzyme is responsible for breaking down a host bacterium's cell wall so that the virus can leave the cell?
Lysozyme
How would Miley's kidney dysfunction lead to signs and symptoms of a swollen abdomen, swollen ankles, and a decreased urine output? (NCLEX style)
Miley's kidneys could not produce sufficient urine, so fluid began to build up in her abdomen and other tissues.
A rapid Strep test is often used in the clinic to determine whether a patient is infected with Streptococcus. After swabbing the patient's throat, the sample is mixed with specified reagents and then applied to a diagnostic strip. As the sample moves up the strip, various lines will appear or not appear, depending on the reaction. The "C" line is the positive control-it should always appear. The "T" line is the test-it should only appear if the result is positive. Two samples come into the clinic lab, and the following results are obtained. How would you interpret these results? (NCLEX style)
Patient 1 has Strep throat; Patient 2's results are inconclusive and must be redone. add notes Patient one shows a line for the control and for the test, indicating that the reaction worked and they are positive. Patient two did not have a control line, so the test must be repeated.
In which stage is the viral DNA introduced into the cell?
Penetration
From which phrase is the term "prions" derived?
Proteinaceous infectious particles
Assume the doctors determined the virus had an RNA genome. Which antiviral would likely be prescribed to treat her infection?
Ribavirin add notes *** Antivirals work to block various stages of viral replication including attachment, penetration, uncoating, viral replication, assembly and release. Given that this virus has an RNA genome, a nucleoside analogue that blocks RNA polymerase may be the most effective treatment. Ribavirin is frequently used to target certain RNA viruses such as Hepatitis C. Although not listed here, if the virus in question was found to be a retrovirus, a nucleoside reverse transcriptase inhibitor may also prove an effective treatment option.
Which disease did Stanley Prusiner first identify as being caused by prions?
Scrapie
Which of the following would be the best way to search for new viruses in old donated blood samples?
Sequencing of viral genetic material following nucleic acid extraction from blood samples. ***Add Note**** Viruses are typically detected through molecular techniques that identify viral genetic material, viral proteins, or antibodies that a patient may have against viral proteins (antigens). Of these methods, nucleic acid detection techniques tend to be more sensitive than antigen-antibody-based tests, and sometimes they are faster. Nucleic acid techniques are also more likely to detect new viruses since these techniques do not require prior characterization of viral antigens.
Which of the following genome types has been observed in viruses? To be marked correct, you'll need to select all true statements, as there may be more than one correct answer
Single-stranded RNA Single-stranded DNA Double-stranded RNA
Which of the following Gram stains could represent a throat swab from a patient with strep throat? (NCLEX style)
Streptococci are spherical microbes arranged in chains.
How is the lytic cycle different from the lysogenic cycle with respect to the infected host cell?
The host cell dies during the lytic stage.
Miley did not go to the doctor because she presumed her sore throat was caused by a virus, and no treatment would be available. Why is it more difficult to treat a viral infection than a bacterial one?
Viruses use our host cell machinery to replicate. Bacteria do not add notes Viruses use our enzymes and building blocks to replicate. Therefore, it is difficult to find a substance that will interfere with viral replication but won't affect us.
Which of the following best describes a prophage?
When a phage genome is integrated into the host cell's chromosome
Lysogenic viral DNA which has integrated into the host genome is referred to as
a prophage.
Epstein-Barr virus is a _____ virus and, therefore, has a _____-based genome
herpes; DNA add notes EBV is a herpes virus. All herpes viruses have DNA genomes.
The rabies virus primarily affects the nervous system. The specificity that the rabies virus has for neuronal host cells is primarily dictated by __________________________.
the spikes that protrude from its viral envelope
Genomic sequencing reveals that Hepatitis C and the unnamed virus share certain key genes. An agglutination test reveals that anti-hepatitis C antibodies react to the unnamed viral antigens. Given the agglutination cross reaction, which of the following is most likely true regarding the shared genes?
The shared genes most likely encode viral surface proteins. Add notes During an infection, the immune system makes antibodies against antigens. Certain viruses, such as influenza, mutate frequently through antigenic drift and antigenic shift. The resulting new strains appear different enough from prior strains that they can escape antibodies hosts may have made against earlier strains. In this experiment, when antibodies from Hepatitis C vaccinated animals were mixed with the unnamed virus, an agglutination reaction developed. In contrast, when antibodies from unvaccinated animals were used, an agglutination reaction did not develop. If we assume (as we were told to do) that the only difference among the animals is their vaccination status, then we can conclude the antibodies animals made against Hepatitis C can recognize antigens on the surface of the new virus. Note, in the experiment whole virus particles were linked to the beads, so only surface antigens would be accessible to the added antibodies.
The researchers discovered another six people who had transfusions around the same time as Jimena and had an exposure to the new virus. The doctors monitored all of the patients over a period of years. They found that viral titers in these patients could shift from being undetectable to being very high in cycles that occurred as frequently as every six months. What does this suggest about the virus
The virus causes a latent, persistent infection Add notes Viral infections may be acute (allowing for immune clearance) or persistent (the virus remains in the host for long periods of time). In an acute nonpersistent infection, viral replication peaks followed by immune clearance of the virus. Latent and chronic infections evade immune clearance and persist in the host. Latent infections exhibit bursts of viral replication with intermittent (silent) periods. Chronic infections exhibit steady viral production that may increase over time. The information provided would not allow us to conclude that the virus is integrated into the host genome. The virus could be maintained episomally like human herpesviruses.
What would be the fate of a lytic bacteriophage if the host cell died prior to the assembly stage?
The virus would not be able to infect new hosts.
How are prions different from other infectious agents?
They lack nucleic acid.
How are viruses different from eukaryotic cells?
They require a host in order to reproduce.
Besides Jose, no one suspected to be infected with the unnamed virus has died of cancer. Does this information rule out the possibility that this is an oncogenic virus? Why or why not?
This virus is possibly an oncogenic virus since infection with an oncogenic virus merely increases cancer risk and does not guarantee that cancer will develop. Add notes Oncogenic viruses are cancer-causing viruses. They include DNA and RNA viruses that may or may not integrate into the host genome. Viruses that cause persistent infections, such as the papillomaviruses, are also associated with cancer. Oncogenic viruses may be spread through several modes of infection including through sexual contact or bodily fluids such as blood or breast milk. For example, human T-lymphotropic viruses (HTLV) are oncogenic viruses that can be transmitted through sexual contact, but they can also be transmitted through bodily fluids such as blood and breast milk.
What is the function of the structural elements of a virus?
To package and protect the viral genome
