1.
What is a virion?
Correct Answer
C. Single virus particle.
Explanation
A virion refers to a single virus particle. It is the complete infectious form of a virus that consists of nucleic acid (either DNA or RNA) enclosed in a protein shell called the capsid. The virion is the fully formed and matured virus particle that is capable of infecting a host cell and replicating its genetic material.
2.
What is the core?
Correct Answer
A. Nucleic acid and surrounding protein shell.
Explanation
The core refers to the nucleic acid and the surrounding protein shell. This means that the core of a virus consists of genetic material (nucleic acid) enclosed within a protective protein coat. The nucleic acid contains the instructions for viral replication and the protein shell provides stability and protection to the genetic material. This explanation is supported by the fact that the other options (major protein component of the shell, single virus particle, and membrane surrounding virus core) do not fully encompass the concept of the core as described.
3.
What is a capsid?
Correct Answer
C. Major protein component of the shell of the core.
Explanation
A capsid is the major protein component of the shell of the core of a virus. It is responsible for protecting the nucleic acid (DNA or RNA) of the virus. The capsid is made up of repeating protein subunits called capsomeres, which come together to form a symmetrical structure. The capsid provides structural integrity to the virus and plays a crucial role in the virus's ability to infect host cells. It also helps in the attachment of the virus to the host cell surface.
4.
What is the envelope?
Correct Answer
D. Membrane surrounding virus core.
Explanation
The correct answer is "Membrane surrounding virus core." This answer is supported by the statement "Membrane surrounding virus core" in the given options. It suggests that the envelope refers to the protective membrane that surrounds the virus core. This explanation aligns with the context of the question, which is asking for the definition or description of the envelope.
5.
Viruses can survive outside of the cell.
Correct Answer
B. False
Explanation
Viruses are obligate intracellular pathogens. They lack metabolic and protein synthesis machinery.
6.
Which of the following is (are) true concerning viruses?
Correct Answer(s)
A. May contain DNA as the genetic material.
B. May contain RNA as the genetic material.
C. Protein shell has an envelope.
D. Protein shell does not have an envelope.
E. They are the smallest of all self-replicating organisms.
Explanation
Viruses can contain either DNA or RNA as their genetic material. Some viruses have DNA, while others have RNA. The protein shell of a virus can have an envelope, which is a lipid membrane surrounding the protein coat. However, not all viruses have an envelope, and some have a protein shell without an envelope. Additionally, viruses are considered the smallest of all self-replicating organisms.
7.
Viruses can use which of the following as hosts?
Correct Answer(s)
A. Bacteria
C. Protozoa
D. Plants
E. Animals
F. Algae
G. Fungi
Explanation
Viruses can use a variety of organisms as hosts, including bacteria, protozoa, plants, animals, algae, fungi, and molds. These organisms provide a suitable environment for viruses to replicate and carry out their life cycle. By infecting these hosts, viruses can hijack their cellular machinery and utilize their resources for their own reproduction. This allows viruses to spread and potentially cause diseases in their host organisms.
8.
Viruses can replicate in the:
Correct Answer
C. Both cytoplasm and nucleus.
Explanation
Viruses can replicate in both the cytoplasm and nucleus. Some viruses replicate in the cytoplasm, where they use the host cell's machinery to produce viral proteins and replicate their genetic material. Other viruses, particularly DNA viruses, can enter the nucleus of the host cell and replicate their genetic material there. This allows them to take advantage of the host cell's transcription and replication machinery. Therefore, viruses have the ability to replicate in both cellular compartments, depending on their specific characteristics and the type of host cell they infect.
9.
Viruses can result in acute death of the host.
Correct Answer
A. True
Explanation
Pathogenesis can range from asymptomatic to acute death.
10.
Match the following terms with the definitions below: Host Range, Susceptibility.1. The capacity of a cell, tissue, or species to support virus replication - qualitatative measurement - number of receptor molecules and ability of host cell to support virus replciation.2. The cells, tissues, species that a virus can productively infect - absolute measurement - determined by receptor availability for virus binding/entry and presence of intracellular cell factors to support virus replication.
Correct Answer
B. Susceptibility = 1, Host Range = 2.
Explanation
The correct answer is Susceptibility = 1, Host Range = 2. This is because the definition provided for Susceptibility matches the term "The capacity of a cell, tissue, or species to support virus replication," which is given for Host Range. Similarly, the definition provided for Host Range matches the term "The cells, tissues, species that a virus can productively infect," which is given for Susceptibility. Therefore, the definitions and terms are correctly matched in this answer.
11.
The capsid provides protection against:
Correct Answer(s)
B. Variations in pH.
C. Variations in temperature.
D. Chemicial composition of the environment.
Explanation
The capsid of a virus is the protein shell that encloses its genetic material. It provides protection against variations in pH, variations in temperature, and the chemical composition of the environment. pH and temperature fluctuations can damage the integrity of the viral genome, so the capsid acts as a barrier to maintain optimal conditions for the virus to survive. Additionally, the capsid helps shield the genetic material from harmful chemicals in the environment.
12.
The virus' structure is a:
Correct Answer
B. Icosahedron.
Explanation
Icosahedron: A solid with 20 triangular faces and 12 vertices related by 2-, 3-, and 5-fold axes of symmetry.
13.
The viral envelope can protect against:
Correct Answer(s)
A. Chemicals.
E. Enzymes.
Explanation
Envelope: A host cell-derived lipid bilary carrying viral glycoproteins that forms the outer laywer of a virus particle. Advantages: protective lipid membrane full of proteins and sugars can protect against chemicals and enzymes. Disadvantages: less stable in the environment.
14.
How do most viruses acquire membranes/envelopes?
Correct Answer
D. By budding through a host cell membrane.
Explanation
Plasma membrane, endoplasmic reticulum, golgi aparatus, or nuclear membrane.
15.
Which of the following is true regarding virus binding?
Correct Answer(s)
A. Requires specific protein receptors.
E. May limit host-cell range AND susceptibility.
Explanation
Specific/non-specific lipids, specific/non-specific carbohydrates. May limit host-cell range AND susceptibility.
16.
Which type of virus fusion/entry is defined as: internalized into endosome - pH changes causes conformation change in envelope proetin and fusion with endosomal membrane and release into cytosol?
Correct Answer(s)
Endocytosis, endocytosis
Explanation
Endocytosis is a process by which cells internalize molecules or particles by engulfing them into a vesicle formed from the cell membrane. In this case, the virus is internalized into an endosome through endocytosis. The change in pH within the endosome triggers a conformational change in the envelope protein of the virus, allowing it to fuse with the endosomal membrane and release its genetic material into the cytosol of the host cell. This mechanism of virus fusion/entry is known as endocytosis.
17.
What are the possible mechanisms for virus fusion/entry into the host cell?
Correct Answer(s)
B. Endocytosis.
D. Penetration through plasma membrane.
E. Fusion with plasma membrane.
Explanation
Fusion with plasma membrane (enveloped) - receptor binding causes conformation change in envelope resulting in fusion with cell membrane. Endocytosis - internalized into endosome - pH changes causes conformation change in envelope protein and fusion with endosomal membrane and release into cytosol. Penetration through plasma membrane - non-enveloped viruses.
18.
Enveloped viruses may enter the host cell through:
Correct Answer
A. Fusion with plasma membrane.
Explanation
Enveloped viruses are a type of virus that have an outer lipid membrane derived from the host cell. This membrane allows the virus to fuse with the host cell's plasma membrane, enabling the virus to enter the cell. Fusion with the plasma membrane is a common mechanism used by enveloped viruses to gain entry into the host cell and initiate infection. Penetration through the plasma membrane refers to the entry of non-enveloped viruses, which do not have a lipid membrane, and is not applicable to enveloped viruses.
19.
Non-enveloped viruses may enter the host cell through:
Correct Answer
B. Penetration through plasma membrane.
Explanation
Non-enveloped viruses are characterized by their lack of an outer lipid envelope. Unlike enveloped viruses, they do not have the ability to fuse with the host cell's plasma membrane. Instead, non-enveloped viruses rely on other mechanisms to enter the host cell, such as penetrating through the plasma membrane. This means that they directly enter the cell by crossing the cell membrane, often using specialized viral proteins or by creating pores in the membrane.
20.
Replication of RNA viruses typically occurs in the:
Correct Answer
D. Cytoplasm
Explanation
may involve specialized "replication complexes"
21.
What enzyme is used in the replication of progeny genomic RNA molecules?
Correct Answer
B. Viral specific RNA polymerase
Explanation
Viral specific RNA polymerase is the correct answer because it is the enzyme responsible for replicating progeny genomic RNA molecules. This enzyme is specific to viruses and plays a crucial role in the viral replication process. It catalyzes the synthesis of RNA using a DNA template, allowing the virus to produce multiple copies of its genomic RNA for the replication of its progeny.
22.
Replication of DNA viruses typically occurs in the:
Correct Answer
C. Nucles
Explanation
DNA viruses typically replicate in the nucleus of the host cell. This is because the host cell's nucleus contains the necessary enzymes and machinery required for DNA replication. The viral DNA enters the nucleus and hijacks the host cell's replication machinery to replicate its own DNA. Once replication is complete, the newly synthesized viral DNA can be used to produce viral proteins and assemble new virus particles. Replication in the nucleus allows the virus to take advantage of the host cell's resources and ensure efficient replication and production of progeny viruses.
23.
For enveloped viruses, assembly typically occurs at the site of replication.
Correct Answer
B. False
Explanation
For enveloped viruses, assembly typically occurs at the site of membrane acquisition - nucleus, ER/golgi, plasma membrane.
24.
What are the ways the virus undergoes budding/release?
Correct Answer(s)
A. Lysis.
C. Budding out of plasma membrane.
E. Exocytosis.
Explanation
Lytic - accumulation of particles until critical mass is achieved - viral signals induce cell death and release of virions.
25.
The majority of viruses are life-threatening.
Correct Answer
B. False
Explanation
It is likely that the majority of viruses cause no disease.
26.
Match the following types of persistent infections with the definitions below: Chronic infections, latent infections.1. Virus is detectable in tissue samples, multiplying at a slow rate; symptoms mild or absent.2. After a lytic cycle, virus enters a dormant phase; generally not detectable, no symptoms; can reactivate and result in recurrent infections.
Correct Answer
A. Chronic infections = 1, Latent infections = 2.
Explanation
The correct answer is Chronic infections = 1, Latent infections = 2. This is because chronic infections are characterized by the virus being detectable in tissue samples and multiplying at a slow rate, while the symptoms are mild or absent. On the other hand, latent infections occur after a lytic cycle, where the virus enters a dormant phase and is generally not detectable, with no symptoms. However, it can reactivate and result in recurrent infections.
27.
What is the best target for the treatment of viral diseases?
Correct Answer
B. Unique viral enzymes.
Explanation
Unique viral enzymes are the best target for the treatment of viral diseases because these enzymes play a crucial role in the replication and survival of the virus. By targeting these enzymes, it is possible to disrupt the virus's life cycle and inhibit its ability to spread and cause harm. Additionally, unique viral enzymes offer a specific target that can be selectively targeted without affecting the host cells, minimizing potential side effects of the treatment.
28.
Which of the following are unique viral enzymes that are targeted for treatment?
Correct Answer
B. Reverse transcriptases.
Explanation
Human immunodeficiency virus type I (HIV-I) reverse transcriptase and herpes simplex virus (HSV) thymidine kinase.
29.
Which of the following is true regarding Ribavirin?
Correct Answer(s)
A. Synthetic nucleoside of guanosine.
B. Approved in US for respiratory syncytial virus (RSV) and in combination with alpha-interferon for hepatitis C virus (HCV)
D. Has in vitro activity against a broad range of both RNA and DNA viruses
Explanation
Has multiple mechanisms of action - nuceloside analog; capping & elongation of RNA (RNA polymerase inhibitor); reverse transcription inhibitor.
Has in vitro activity against a broad range of both RNA and DNA viruses including flaviviruses, paramyxoviruses, bunyaviruses, arenaviruses, retroviruses, herpesviruses, adenoviruses, and poxviruses.
30.
Single Stranded, enveloped DNA viruses cause infections in humans.
Correct Answer
B. False
Explanation
DS Enveloped
SS nonenveloped
DS Noneveloped all do
31.
Which of the following is not an enveloped DNA virus?
Correct Answer
D. Adenoviruses
Explanation
adenoviruses are DS NONenveloped!
32.
Poxviruses replicate
Correct Answer
B. In the Cytoplasm
Explanation
Poxviruses replicate in the cytoplasm. This means that the replication process of these viruses occurs outside the nucleus of the host cell. Unlike most other viruses that replicate within the nucleus, poxviruses have the ability to replicate in the cytoplasm due to their large genome size and complex replication machinery. This allows them to evade certain host defense mechanisms and carry out their replication cycle independently in the cytoplasmic compartment of the infected cell.
33.
Which of the following has the largest genome of all human viruses
Correct Answer
A. Poxvirus
Explanation
single linear dsDNA molecule of 130-300 kb with hairpins at either end
34.
Which of the following small poxes is most viruletn
Correct Answer
A. Variola major
Explanation
Variola major – highly virulent, caused toxemia, shock, and intravascular coagulation
35.
Humans are susceptible to monkeypox, mousepox, and cowpox
Correct Answer
B. False
Explanation
Humans are susceptible to monkeypox and cowpox
36.
Herpesviruses replicates
Correct Answer
B. Within the nucleus
Explanation
Herpesviruses replicate within the nucleus. This means that the replication process of herpesviruses occurs inside the nucleus of the host cell. This is a characteristic feature of herpesviruses, as they utilize the host cell's machinery and resources within the nucleus to replicate their genetic material and produce new viral particles. Replication within the nucleus allows the virus to efficiently utilize the cellular machinery and ensure successful reproduction.
37.
Herpesviruses are large enveloped icosahedral dsDNA
Correct Answer
A. True
Explanation
The statement is true because herpesviruses are indeed large enveloped icosahedral dsDNA viruses. This means that they have a large size, with an envelope surrounding their protein capsid, and their genetic material is double-stranded DNA.
38.
Which of the following is not a herpesvirus?
Correct Answer
C. Adenovirus
Explanation
Adenovirus is not a herpesvirus. Herpes simplex 1, herpes simplex 2, varicella zoster virus, and Epstein-Barr virus are all types of herpesviruses. Roseola is caused by human herpesvirus 6 or 7. Adenovirus is a separate type of virus that can cause respiratory, gastrointestinal, and eye infections.
39.
HSV-2 can only be spread when lesions are visible.
Correct Answer
B. False
Explanation
active lesions most significant source; genital herpes can be transmitted in the absence of lesions
40.
Which HSV-1 produces fever blisters, cold sores and is the most common recurrent HSV-1 infection
Correct Answer
A. Herpes labialis
Explanation
Herpetic gingivostomatitis – infection of oropharynx in young children; fever, sore throat, swollen lymph nodes
Herpetic keratitis – ocular herpes – inflammation of eye; gritty feeling in the eye, conjunctivitis, sharp pain, and sensitivity to light
41.
Which treatment option is specifically activated by HSV induced thymidine kinase enzyme
Correct Answer
A. Acyclovir
Explanation
Acyclovir is specifically activated by the HSV induced thymidine kinase enzyme. This enzyme is produced by the herpes simplex virus (HSV) and is responsible for converting acyclovir into its active form. Once activated, acyclovir inhibits viral DNA replication and prevents the spread of the virus. Famciclovir, penciclovir, and valacyclovir are also antiviral medications used to treat HSV infections, but they are not specifically activated by the HSV induced thymidine kinase enzyme. Topical medications may be used to relieve symptoms but do not specifically target the viral replication process.
42.
Varicella-Zoster Virus (VZV) is transmitted by
Correct Answer(s)
A. Respiratory droplets
C. Direct contact
Explanation
Varicella-Zoster Virus (VZV) is transmitted through respiratory droplets and direct contact. Respiratory droplets are tiny particles that are released when an infected person coughs, sneezes, or talks, and can be inhaled by others. Direct contact refers to touching the fluid from the rash of an infected person or coming into contact with their saliva or mucus. These modes of transmission allow the virus to easily spread from person to person. Other routes mentioned, such as oral-fecal route and sexual transmission, are not associated with the transmission of VZV.
43.
Cytomegalovirus – CMV is transmitted via
Correct Answer(s)
A. Saliva
B. Respiratory mucus
C. Cervical secretions
D. breast milk
E. Urine
F. Semen
Explanation
Cytomegalovirus (CMV) is transmitted through various bodily fluids, including saliva, respiratory mucus, cervical secretions, breast milk, urine, and semen. These fluids can contain the virus and can be a source of transmission from an infected individual to a non-infected individual. It is important to note that CMV can be transmitted through close contact, such as kissing, sexual intercourse, sharing utensils or toothbrushes, and from mother to baby during pregnancy, childbirth, or breastfeeding. Therefore, it is crucial to practice good hygiene and take necessary precautions to prevent the spread of CMV.
44.
Transmission of Epstein-Barr Virus (EBV) can be direct, oral contact and contamination with saliva
Correct Answer
A. True
Explanation
The statement is true because the Epstein-Barr Virus (EBV) can be transmitted through direct contact, oral contact, and contamination with saliva. This means that the virus can be spread through activities such as kissing, sharing utensils or drinks, and even through coughing or sneezing. Saliva plays a significant role in the transmission of EBV, as it contains the virus and can easily be transferred from one person to another. Therefore, it is important to practice good hygiene and avoid close contact with infected individuals to prevent the spread of EBV.
45.
By mid-life, 90-95% of all people are infected with Epstein-Barr Virus (EBV)
Correct Answer
A. True
Explanation
The given statement states that by mid-life, 90-95% of all people are infected with Epstein-Barr Virus (EBV). This means that a large majority of individuals are infected with EBV by the time they reach middle age. This suggests that EBV is a highly prevalent virus that is commonly transmitted among the population.
46.
Over 70% of MS patients show signs of which infection
Correct Answer
D. HHV-6
Explanation
Also, there is aSignificant relationship between HHV-6 and Hodgkin’s lymphoma, oral carcinoma, certain T-cell leukemias
47.
Hep A, B and C are all RNA viruses.
Correct Answer
B. False
Explanation
Only Hep A and Hep C are RNA viruses. Hep B is a DNA virus.
48.
HBV has an unusual genome containing both double- and single-stranded DNA
Correct Answer
A. True
Explanation
HBV, or Hepatitis B virus, is known for having a unique genome that consists of both double-stranded and single-stranded DNA. This is unlike most other viruses, which typically have either double-stranded or single-stranded genomes. The presence of both types of DNA in the HBV genome allows for its replication and transcription processes to occur in a complex manner. This characteristic of HBV's genome plays a significant role in its life cycle and pathogenesis.
49.
The Adenoviruses are spread by
Correct Answer(s)
A. Respiratory secretions
C. Ocular secretions
D. Fecal-oral
Explanation
The Adenoviruses can be spread through various routes, including respiratory secretions, ocular secretions, and the fecal-oral route. Respiratory secretions, such as coughing or sneezing, can release the virus into the air and infect others who inhale it. Ocular secretions, such as tears or discharge from the eyes, can also contain the virus and potentially spread it to others through direct contact. Additionally, the virus can be transmitted through the fecal-oral route, where contaminated fecal matter is ingested, often due to poor hygiene practices or contaminated food or water.
50.
All HPV types increase risk for developing reproductive cancer
Correct Answer
B. False
Explanation
Nine HPV types increase risk for developing reproductive cancer
2 account for 70% of metastatic tumors