Mastering Microbiology Chapter 13
They require a host in order to reproduce.
They do not contain genetic material.
They do not contain enzymes.
They do not contain protein.
To provide a source of energy for the virus
To use all of the cell proteins
To package and protect the viral genome
An infected cell entering the logarithmic phase of growth
Normal cell division of an infected cell
Exposure to UV light
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.
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.
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?)
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
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.
Arrange the following statements in chronological order .
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.
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 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.
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.
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.
-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
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
-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
-an excessive inflammatory response leading to extensive tissue damage
-the virus undergoes antigenic changes on a regular basis
-overall decrease in the replication rate of influenza
-a decrease in the release of viral particles from the cell