Mic 541 Exam 4 - Virology - Part 1

Icosahedron: A solid with 20 triangular faces and 12 vertices related by 2-, 3-, and 5-fold axes of symmetry.

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.

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.

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.

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.

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.

Pathogenesis can range from asymptomatic to acute death.

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.

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.

Antigenic shift refers to the recombination of whole genes or DNA segments in the influenza A virus. This process can lead to the emergence of new strains that are significantly different from previous strains, making them more likely to cause pandemics. Therefore, the statement that antigenic shift causes pandemics with Influenza A is true.

Viruses are obligate intracellular pathogens. They lack metabolic and protein synthesis machinery.

Plasma membrane, endoplasmic reticulum, golgi aparatus, or nuclear membrane.

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.

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.

may involve specialized "replication complexes"

Only Hep A and Hep C are RNA viruses. Hep B is a DNA virus.

Influenza - Enveloped Segmented Single-Stranded RNA Viruses

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.

Causes distemper in cats, enteric disease in dogs, fatal cardiac infection in puppies
B19 cause of erythema infectiosum (fifth disease); rash of childhood

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.

Hemagglutinin (H) is the correct answer because it is an influenza envelope protein that facilitates binding to host cells and fusion. Hemagglutinin allows the virus to attach to sialic acid receptors on the surface of host cells, which is the first step in the viral entry into the cell. It also mediates the fusion of the viral envelope with the host cell membrane, allowing the virus to enter the cell and initiate infection. Neuraminidase (N) is involved in the release of newly formed viral particles from infected cells, while M2 is a proton channel protein that plays a role in viral replication.

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.

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.

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.

Variola major – highly virulent, caused toxemia, shock, and intravascular coagulation

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.

Human immunodeficiency virus type I (HIV-I) reverse transcriptase and herpes simplex virus (HSV) thymidine kinase.

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.

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.

It is likely that the majority of viruses cause no disease.

active lesions most significant source; genital herpes can be transmitted in the absence of lesions

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.

Neuraminidase (N) is the correct answer because it is an influenza envelope protein that plays a crucial role in viral budding and release. Neuraminidase helps the newly formed influenza virus particles to detach from the infected host cell surface by cleaving sialic acid residues on the cell surface. This allows the virus to spread and infect other cells. Hemagglutinin (H) is responsible for binding the virus to the host cell, while M2 is involved in the uncoating of the virus inside the host cell.

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.

single linear dsDNA molecule of 130-300 kb with hairpins at either end

Humans are susceptible to monkeypox and cowpox

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

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.

adenoviruses are DS NONenveloped!

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.

Nine HPV types increase risk for developing reproductive cancer
2 account for 70% of metastatic tumors

Type B influenza only undergoes antigenic drift and is not known to undergo antigenic shift. Antigenic drift refers to small changes in the virus's surface proteins, allowing it to evade the immune system and cause repeated infections. On the other hand, antigenic shift is a major change in the virus's surface proteins, resulting in the emergence of a new strain that can cause pandemics. Type B influenza typically causes milder illness compared to type A, and its genetic changes are more gradual, leading to the absence of antigenic shift events.

For enveloped viruses, assembly typically occurs at the site of membrane acquisition - nucleus, ER/golgi, plasma membrane.

Antigenic DRIFT (random DNA mutations) in Influenza A is what causes the new seasonal strains we see most years

orthomyovirus (RNA virus that causes influenza)replication occurs in the nucleus, not the cytoplasm.

Specific/non-specific lipids, specific/non-specific carbohydrates. May limit host-cell range AND susceptibility.

DS Enveloped
SS nonenveloped
DS Noneveloped all do

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.

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.

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.