Mastering Microbiology Chapter 13

Mastering Microbiology Chapter 13

How does specialized transduction differ from regular lysogeny?
The prophage in specialized transduction carries with it pieces of the host chromosomal DNA.
What happens to the packaged DNA of a specialized transduced phage when it infects a new recipient cell?
The host DNA integrates, with the prophage, into the new recipient chromosome
How can specialized transduction contribute to the transfer of antibiotic resistance genes in a bacterial population?
The prophage takes an antibiotic resistance gene with it and is packaged with the newly synthesized viral DNA.
Which of the following is true concerning a lysogenic viral replication cycle?
During lysogeny, the viral genome integrates into the host DNA, becoming a physical part of the chromosome.
How are viruses different from cells?

They require a host in order to reproduce.
They do not contain genetic material.
They do not contain enzymes.
They do not contain protein.

They require a host in order to reproduce.
What is the function of the structural elements of a virus?

To provide a source of energy for the virus
To use all of the cell proteins
To package and protect the viral genome

To package and protect the viral genome
Lysogenic viral DNA integrating into the host genome is referred to as

a prophage.

a prophage
Which of the following events might trigger induction of a temperate bacteriophage?

An infected cell entering the logarithmic phase of growth
Bacterial conjugation
Normal cell division of an infected cell
Exposure to UV light

Exposure to UV light
How is the lytic cycle different from the lysogenic cycle with respect to the infected host cell?

The viral DNA may integrate into the host genome during the lytic stage.
The host cell is allowed to live during the lytic stage.
The host cell can only divide during the lytic stage.
The host cell dies during the lytic stage.

The host cell dies during the lytic stage.
What is the fate of the prophage during the lysogenic stage?

It is packaged into viral proteins and maintained until the host is exposed to an environmental stress.
It is degraded by the activity of host defense enzymes.
It is released from the cell by lysing the cell.
It is copied every time the host DNA replicates.

It is copied every time the host DNA replicates.
How do naked viruses differ from enveloped viruses in their attachment/penetration phase?
Their nucleic acids are injected into the cell.
Which virus employs the use of an RNA-dependent RNA polymerase?
+RNA viruses
Which of the following viruses is transcribed from RNA to DNA to RNA during the replication cycle?
Which type of virus would produce viral glycoproteins to be expressed on the host cell membrane?
Enveloped viruses
Which of the following can be used directly as messenger RNA?
We sometimes are able to generate antibodies (immune system proteins) that bind to and cover up some of the proteins on the outermost portion of a virus while it is in the bloodstream. This renders the virus unable to reproduce. Which step of viral replication are antibodies directly preventing
Enveloped viruses have a layer of lipids surrounding their capsid. This envelope is made mostly of host cell membrane. In which step does the virus acquire this envelope?
What occurs during viral uncoating?
the capsid breaks apart, releasing the viral genome
Which of the following is true regarding cultivation and isolation of animal viruses?
Diploid cell culture lines, developed from human embryos, are widely used for culturing viruses that require a human host
From which phrase is the term “prions” derived?
Proteinaceous infectious particles
In what year did Stanley Prusiner discover prions?
Which disease did Stanley Prusiner first identify as being caused by prions?
How are prions different from other infectious agents?
They lack nucleic acid
The normal function of the PrP protein in mammals is believed to be:
assisting in normal synaptic development and function.
How do normal prion proteins (PrP) differ from the infectious prion proteins?
Normal PrP have alpha-helices; infectious PrP have beta-pleated sheets.
How does the number of infectious prions increase?
Prions transform normal proteins into the misfolded beta-pleated sheet configuration; therefore, prions multiply by conversion
Why are the beta-pleated multimers of PrP potentially pathogenic?
The multimers are more stable and resistant to protease.
What disease does the human herpesvirus-1 cause?

canker sores
cold sores or fever blisters
infectious mononucleosis

cold sores or fever blisters

Correct! Cold sores or fever blisters are the painful, short-lived vesicles that form near the outer margins of the lips. It is transmitted via oral and respiratory routes. In the United States, a large percentage of the population is infected with this virus during infancy, when the virus is passed via respiratory droplets from family members. (Who can resist kissing a baby?)

What Does Old Age have to Do with It?
Barbara, a 68-year-old retired schoolteacher, was beside herself. Her husband Bob had passed away only a month ago, and a week later, her youngest daughter, 40-year-old Maria, had moved back in with her. Maria was in the process of divorcing her husband and was seeking sole custody of her three children. The children, ages 6, 8, and 12, were also living in the house with their grandmother. Barbara enjoyed playing games, gardening, and taking walks with her family, and on the whole did not mind having the extra company. The extra cooking and cleaning were taking a toll on her health, however. One morning, Barbara woke up with excruciating pain on her right rib cage. When she looked at her side in the bathroom mirror, she found that she had an extremely red rash with little vesicular lesions. The rash was localized to her right side and looked very similar to Image A. Concerned about the rash and the amount of pain associated with it, Barbara phoned her physician’s office and made an appointment for that afternoon.
During her appointment, Barbara discusses her current and previous medical history with Dr. Jones. Up until this rash appeared, Barbara had been a healthy individual. She is the appropriate weight for her height, and her blood counts have always been within normal ranges. As an adult, she rarely has gotten sick, even with minor illnesses such as colds. As a child, Barbara had received all of the appropriate vaccinations as scheduled and had been a relatively healthy young lady. In fact, Barbara could remember missing school for illnesses only twice during her entire school career: once when she had chickenpox in second grade, and once in high school when she had a severe case of the flu. Barbara’s medical history confirms Dr. Jones’s suspicion of a latent infection, so there is no need for sample collection.
After asking a few more questions about her medical history, Dr. Jones asks Barbara about her current living situation. Barbara mentions that her grandchildren are living with her. Dr. Jones asks about their general health. Barbara responds that the 6-year-old is getting over a cold, but that overall they are healthy individuals. Dr. Jones gives Barbara a prescription for acyclovir and tells her to come back if she has any further complications.
Which of the following best describes Barbara’s condition?
influenza caused by Influenzavirus
shingles caused by the herpes zoster virus
cold sores caused by human herpesvirus-1
smallpox caused by the smallpox (variola) virus
shingles caused by the herpes zoster virus

As a child, Barbara was infected with the varicella virus and contracted chickenpox. Though she recovered from the chickenpox, the virus was able to enter the peripheral nerves and eventually the central nerve ganglion, where it persists as viral DNA hidden from her immune response. As a result of factors in her life, Barbara’s virus was reactivated and traveled along the peripheral nerves to the cutaneous sensory nerves of the skin. This new outbreak produces the rash characteristic of a shingles infection. The occurrence of shingles is 10% to 20% in individuals who have had chickenpox.

What is the correct sequence of events for the replication of a DNA virus?
Arrange the following statements in chronological order .
1. virions attach to the host cells.
2. viral DNA is released into the nucleus of the host cell
3. enzymes required for multiplication of viral DNA are produced via transcription and translation
4. a copy of the DNA is made
5. capsid and other structural proteins are manufactured
6. virions are assembled to form complete viruses and are released from the host cell

Correct! Viruses depend on host cells for replication. The herpes zoster virus is a DNA virus. It enters the host cell by attaching to host cell receptors. Once inside, the virion is uncoated to release the DNA into the nucleus of the host cell. “Early” genes, typically used for viral replication, are transcribed using the host’s RNA polymerase. Viral DNA is then replicated to produce multiple copies of the DNA. The remaining components of a virion are the produced via transcription and translation of “late” genes. Capsid proteins then migrate to the nucleus of the host cell. Maturation occurs when the capsid proteins and viral DNA combine to form a complete virus. The virions are then released from the host cell to go and infect new host cells. Image C diagrams the replication of papovavirus, a DNA virus similar to herpesvirus.

Which of the following factors could have contributed to Barbara’s development of shingles?

her daughter and grandchildren moving into her house shortly after the death of her husband
the vaccinations that Barbara received as a child
her age, 68
a new exposure to the varicella virus

-her daughter and grandchildren moving into her house shortly after the death of her husband
-her age, 68

Many factors can contribute to reactivation of a latent virus. Research has yet to narrow it down to one thing, but stress, old age, and a change in the host’s immune system have been linked to viral reactivation.

Barbara is worried about spending time with her grandchildren while being treated for shingles. Can her grandchildren contract chickenpox or shingles from spending time with their grandmother?

Yes. Because they are young, the grandchildren are susceptible to both chickenpox and shingles.
Yes. The grandchildren are susceptible because they do not have natural immunity against chickenpox or shingles.
No. Because of their ages, the grandchildren have most likely been vaccinated against the chickenpox. They are also safe from contracting shingles because they are young.
No. The children are safe from contracting the virus because Barbara is not contagious.

No. Because of their ages, the grandchildren have most likely been vaccinated against the chickenpox. They are also safe from contracting shingles because they are young.

Correct! The grandchildren are ages 6, 8, and 12, which means that the varicella vaccine has been an available for all of them. The grandchildren are school-aged and were most likely required to receive the chickenpox vaccine before starting school. If they contracted the virus from Barbara, it would result in a mild form of the rash. This is common in previously vaccinated individuals and is called “breakthrough varicella.” The grandchildren would not contract shingles from Barbara because this disease is rare in individuals younger than 20.

Which of the following are symptoms of influenza infection?
-muscle pain
Drag each one of the labels onto the figure to identify the function of each structure.
-assists the virus in exiting the cell after reproduction
-protects the viral nucleic acid
-recognizes and attaches to host cells
-contains antigenic determinants

-contains the viral genetic information

Arrange the following statements in the order that best describes the sequence of events involved in the replication of influenza.
1. hemagglutinin spikes attach to host cells
2. influenza enters the host cell
3. nucleic acid enters the host cytoplasm
4. influenza proteins are synthesized
5. influenza nucleic acid is packaged in a capsid
6. influenza particles bud from the cell, releasing the virus into the surrounding environment
Which of the following statements regarding antigenic shift are true?
-little immunity to virus strains resulting from antigenic shift exists in the population.
-viral strains resulting from antigenic shift contain RNA segments from different species.
-antigenic shift results in a major change in the genetic composition of the virus
Predict which of the following are reasonable outcomes of the cytokine storm during the 1918 flu pandemic.
-increased fluid in the lungs and labored breathing
-an excessive inflammatory response leading to extensive tissue damage
What are some of the current challenges to production of the influenza vaccine?
-in order to yield a vaccine, the virus must be produced in eggs
-the virus undergoes antigenic changes on a regular basis
Predict which of the following would be outcomes of treatment with Tamiflu.
-an increase in the ability of the immune system to combat the infection
-overall decrease in the replication rate of influenza
-a decrease in the release of viral particles from the cell
In which stage is the viral DNA introduced into the cell?
In which stage does formation of mature viruses occur?
The host DNA is usually degraded during which stage?
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

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