Learn Virology - Biology Of Virus Quiz

Viruses are microscopic infectious agents that can only replicate inside the cells of a host organism. Unlike bacteria, they do not have the ability to undergo binary fission, which is a form of asexual reproduction. Bacteria, on the other hand, are relatively larger in size compared to viruses. Additionally, viruses replicate by using the host's cellular machinery, whereas bacteria can replicate both with and without a host.

Single stranded positive sense RNA viruses have nucleic acid that functions directly as mRNA. This means that the RNA of these viruses can be directly translated by the host cell's ribosomes to produce viral proteins. These viruses do not need to undergo transcription to produce mRNA, as their RNA already serves as mRNA. Examples of single stranded positive sense RNA viruses include the common cold virus (rhinovirus) and the SARS-CoV-2 virus that causes COVID-19.

Programmed cell death, also known as apoptosis, is a natural process by which cells in multicellular organisms undergo controlled self-destruction. Some viruses have evolved mechanisms to induce programmed cell death in host cells during their release. This antiviral effect occurs because the destruction of infected cells prevents the virus from spreading to neighboring cells and further infecting the host. Therefore, the statement that programmed cell death induced by some viruses during release has an antiviral effect is true.

Viruses are infectious agents that contain either double or single stranded RNA or DNA. These genetic materials are surrounded by a protein core. Viruses are not considered living organisms as they cannot replicate on their own and require a host cell to reproduce. They are often referred to as obligate intracellular parasites as they rely on the cellular machinery of the host to replicate and cause infection. The statement "contain double or single stranded RNA or DNA" accurately describes the genetic makeup of viruses.

Glycoproteins are commonly associated with virus spikes. Virus spikes are protein structures that protrude from the surface of a virus and play a crucial role in the attachment and entry of the virus into host cells. These spikes are often glycoproteins, meaning they have sugar molecules attached to them. The presence of glycoproteins on virus spikes allows the virus to recognize and bind to specific receptors on the surface of host cells, facilitating viral entry and infection.

DNA viruses are best linked to transcription in the host nucleus because DNA viruses replicate and transcribe their genetic material using the host cell's machinery. Unlike RNA viruses, which can directly use their RNA as mRNA, DNA viruses require transcription in the host nucleus to produce mRNA for protein synthesis. This process involves the viral DNA being transcribed into mRNA by the host cell's RNA polymerase enzyme. Therefore, transcription in the host nucleus is the most appropriate option for linking DNA viruses.

Prions are likely to accumulate in the brain and spinal cord. Prions are infectious proteins that can cause neurodegenerative diseases, such as Creutzfeldt-Jakob disease and mad cow disease. Unlike viruses, which require genetic material like DNA or RNA to replicate, prions are composed solely of misfolded proteins. These misfolded proteins can induce other normal proteins to adopt the abnormal conformation, leading to a chain reaction and accumulation of prions in the brain and spinal cord. This accumulation disrupts normal cellular processes and causes the characteristic symptoms of prion diseases.

Nonenveloped viruses are released from the host cell by cell lysis, which means the host cell is ruptured or destroyed, leading to the release of the viral particles. This is in contrast to enveloped viruses, which are released by budding, where the viral particles are released from the host cell by budding off from the cell membrane without causing cell lysis. Therefore, the correct answer is "released on cell lysis".

Single stranded negative sense RNA viruses use the genome as a template to make mRNA transcripts corresponding to each viral gene. These viruses have a single stranded RNA genome that is complementary to the viral mRNA. The viral RNA polymerase recognizes this negative sense RNA and uses it as a template to synthesize mRNA transcripts that are then translated into viral proteins.

In the acute phase of viral infection, multiple rounds of replication occur as the virus rapidly multiplies within the host. This leads to a high viral load and the manifestation of symptoms. In contrast, during the latent phase, the virus remains dormant and does not actively replicate. Therefore, multiple rounds of replication are a characteristic of the acute phase but not the latent phase of viral infection.

The correct answer is "exposed regions of capsid proteins". Nonenveloped viruses do not have a lipid envelope, so they cannot use glycoproteins for adsorption. They also do not utilize type III secretion systems. Instead, nonenveloped viruses attach to specific sites on the host cell by binding to exposed regions of the capsid proteins.

Enteroviruses enter the body at one specific site and then cause disease before spreading to other tissues. This means that they initially infect a specific site, such as the respiratory or gastrointestinal tract, and then can spread to other organs or tissues, leading to various symptoms and manifestations of the disease. This characteristic distinguishes enteroviruses from other viruses that may replicate and cause disease at the same site. Additionally, it is not true that enteroviruses cause equal symptoms in children and adults, as the severity and manifestations of the disease can vary depending on the individual's age and immune response.

Serological studies involve analyzing blood samples to detect the presence of specific antibodies produced in response to a viral infection. In the case of virus DX, comparing the titers (levels) of antibodies in the acute phase (early stage of infection) and convalescent phase (recovery stage) can provide valuable information. A significant increase in antibody titers between the two phases indicates an active immune response, suggesting a recent infection. This method helps in diagnosing viral infections and monitoring the progression of the disease.

Interferons are proteins that play a crucial role in the immune response against viral infections. They are produced by various cells in the body, including leukocytes. While beta interferons are indeed produced by leukocytes, it is not the best description of interferons. Interferons are not induced by viruses only; they can also be induced by other stimuli such as bacteria and tumors. The correct answer is that interferons inhibit protein synthesis mechanisms, which is one of their key functions in limiting viral replication within infected cells. Gamma interferon, on the other hand, is induced by fibroblasts and T cells and has various immune-regulatory functions.

Vaccination of children can sometimes lead to virus-induced immunopathology. This occurs when the immune response triggered by the vaccine results in an excessive or inappropriate immune reaction, causing damage to the body's own tissues. This can happen in rare cases where the vaccine stimulates an overactive immune response or when the vaccine fails to provide complete protection, leading to a heightened immune reaction upon subsequent exposure to the virus. It is important to note that the benefits of vaccination far outweigh the risks, and instances of vaccine-induced immunopathology are extremely rare.

double stranded RNA virus

The correct answer is antibody response. Antibodies are proteins produced by the immune system in response to an infection. They bind to specific antigens on the surface of viruses, preventing them from entering host cells and inhibiting early steps of viral replication. This immune response helps to prevent reinfection by the same virus. CMI (cell-mediated immunity) and interferons also play important roles in the immune response to viral infections, but they do not specifically inhibit early steps of viral replication like antibodies do.

Togaviridae is a single stranded RNA virus. It is a family of viruses that includes the alphaviruses and rubiviruses. These viruses have a positive sense RNA genome, meaning that the RNA can be directly translated into proteins by the host cell's machinery. The single stranded RNA is enclosed within a protein coat, forming a nucleocapsid. Togaviridae viruses are known to cause diseases such as chikungunya and rubella.

RNA dependent DNA polymerase

Prions are best described as proteins similar to that of normal cell. Prions are misfolded proteins that can cause normal proteins to also misfold, leading to the formation of aggregates in the brain. They do not contain nucleic acid and are not surrounded by an infectious protein capsid. Prions are not susceptible to proteolytic enzymes and cannot replicate without a helper virus.

Polyomaviridae is a double stranded DNA virus. This family of viruses is characterized by their circular double stranded DNA genome. They are small, non-enveloped viruses that infect a wide range of vertebrates, including humans. Polyomaviridae includes several well-known viruses such as JC virus and BK virus, which can cause serious diseases in immunocompromised individuals. The double stranded DNA nature of these viruses allows for efficient replication and transcription of their genetic material.

The given correct answer states that non enveloped viruses freely cross the plasma membrane. This means that these viruses are able to enter and exit cells without any specific sites or mechanisms. Unlike enveloped viruses, which require specific receptors or endocytosis to enter cells, non enveloped viruses can pass through the plasma membrane without any barriers. This characteristic allows them to easily infect and spread within host cells.

A weakened cellular immunity (CMI) will make the elimination of the infection the most difficult. CMI plays a crucial role in fighting viral infections by activating immune cells, such as T cells, to directly kill infected cells. If the CMI is weakened, the immune response against the viral infection will be compromised, making it harder to eliminate the infection. The other options, such as defective complement, low antibody response, and age, may also contribute to the difficulty in eliminating the infection, but weakened CMI is the most significant factor in this scenario.

A defective virus is a virus that needs simultaneous infection. This means that it requires the presence of another virus in order to replicate and cause an infection. Unlike a normal virus, which can infect cells on its own, a defective virus relies on co-infection with a helper virus to complete its life cycle. Without simultaneous infection, the defective virus is unable to replicate and cause an infection.

During hematogenous spread, bacteria can spread through the blood and then replicate in different parts of the body. This process can occur without causing any noticeable symptoms, which is known as being asymptomatic. It is also possible for the infection to progress without any prodromal symptoms, which are early signs or symptoms that may precede the onset of a disease. Therefore, both options B and C are true statements.

Capsids of viruses are protein coats that enclose and protect the viral genetic material. One of the true statements about capsids is that they self-assemble, meaning that they spontaneously come together to form the complete capsid structure without the need for external assistance. This process is driven by the interactions between the viral proteins. Therefore, the correct answer is "self assembles".

The chronic phase of viral infection is described as being caused by RNA viruses. This means that during the chronic phase, the infection is caused by viruses that have RNA as their genetic material. This phase is characterized by a long-term, persistent infection that can last for years or even a lifetime. In contrast, acute viral infections are typically caused by DNA viruses and have a shorter duration. The presence of viral particles may vary during the chronic phase, but they are generally present in lower levels compared to the acute phase. The chronic phase can occur in individuals with competent immune systems, meaning their immune system is functioning properly.