Only A Genius Can Pass This Microbiology Test! Quiz

Necrotic lesions are localized areas of destruction that occur on plants infected by a virus. These lesions are characterized by dead or dying tissue, which is a result of the virus damaging the plant cells. Necrotic lesions can vary in size, shape, and appearance depending on the specific virus and host plant involved. They are an important symptom for diagnosing viral infections in plants and can have significant impacts on crop yield and overall plant health.

Icosahedral viruses are made up of ring- or knob-shaped units known as capsomers. These capsomers come together to form the overall structure of the virus.

Viruses that have polyhedrons with 20 sides are said to have icosahedral symmetry. Icosahedral symmetry refers to a geometric arrangement in which the virus's structure exhibits 20 identical triangular faces, forming a symmetrical polyhedron. This type of symmetry is commonly found in many viruses, including the rhinovirus and the adenovirus. The icosahedral shape allows the virus to efficiently package its genetic material while maintaining stability and protecting it from external factors.

Peplomers are glycoprotein spikes that are found on the outer surface of the viral envelope. These spikes play a crucial role in the attachment of the virus to host cells and in facilitating viral entry into the host cell. They are involved in the recognition and binding of specific receptors on the host cell surface, allowing the virus to gain entry and initiate infection. Peplomers are commonly found in enveloped viruses, such as the coronavirus, and are important targets for antiviral therapies and vaccine development.

Enveloped viruses have an outer envelope made up of lipids, which allows them to fuse with the host cell's membrane. This fusion enables the virus to enter the host cell and release its genetic material (nucleocapsid) into the cell. Therefore, the statement is true.

Cytopathic effects refer to the microscopic or macroscopic degenerative changes or abnormalities that occur in infected host cells and tissues. These effects are caused by the infection and can include cell death, changes in cell morphology, and alterations in cellular function.

Enveloped viruses are able to enter host cells by being engulfed within coated vesicles through a process called endocytosis. This allows the virus to be enclosed in a membrane-derived vesicle and transported into the cell. Once inside, the virus can then release its genetic material and initiate infection. This mechanism of entry is common among enveloped viruses, which have a lipid envelope surrounding their protein capsid.

Small viruses are able to package more information into their small genomes by using overlapping genes. This means that the same base sequence is read in more than one reading frame, allowing for multiple genes to be encoded within a single stretch of DNA. This strategy maximizes the genetic information that can be stored in the genome, making it more efficient and compact. Therefore, the statement is true.

The available evidence supports the proposal that prion diseases are caused by infectious proteins. This suggests that these diseases can be transmitted from one individual to another through the transmission of these abnormal proteins. The consistency of the evidence strengthens the belief that prion diseases are indeed caused by infectious proteins.

Icosahedral and helical are indeed the most common capsid morphologies. The icosahedral shape is characterized by a symmetrical arrangement of 20 equilateral triangular faces, while the helical shape consists of a spiral arrangement of protein subunits. These two morphologies are commonly observed in viruses and play a crucial role in protecting the viral genetic material. Therefore, the statement "The most common capsid morphologies are icosahedral and helical" is true.

Viruses such as MS2 and Qß are able to pack additional information into their genomes by utilizing overlapping genes. This means that multiple genes can be encoded within the same region of the viral genome, allowing for a more compact and efficient use of genetic material. This mechanism enables these viruses to maximize the amount of genetic information they can carry within their limited genome size. Therefore, the statement "Viruses such as MS2 and Qß pack additional information into their genomes through the use of overlapping genes" is true.

Viruses can exhibit different types of symmetry in their structure. Icosahedral symmetry refers to a symmetrical arrangement of subunits in a virus, forming a roughly spherical shape with 20 identical triangular faces. Helical symmetry, on the other hand, describes a spiral arrangement of subunits, resulting in a cylindrical or rod-like shape. Therefore, the correct answer is "icosahedral and helical" as these are the two major types of symmetry found in viruses.

Prions are infectious proteins that can cause diseases in humans and animals. The mechanism of pathogenesis by prions involves a conformational change in the normal prion protein (PrP) to an abnormal form. This abnormal form of PrP is highly stable and can induce other normal PrP molecules to adopt the abnormal conformation. This leads to the accumulation of the abnormal PrP, causing damage to the nervous system and eventually resulting in neurodegenerative disorders known as prion diseases. Therefore, the statement that the mechanism of pathogenesis by prions involves a conformational change in the PrP to an abnormal form is true.

The statement is false because there are known human diseases that have been linked to prions. Prion diseases, also known as transmissible spongiform encephalopathies, are caused by abnormal proteins called prions. These diseases include Creutzfeldt-Jakob disease, variant Creutzfeldt-Jakob disease, and fatal familial insomnia. Prion diseases can cause severe neurological symptoms and are often fatal.

Enveloped viruses can enter host cells by being engulfed within coated vesicles through a process called endocytosis. This means that the virus is enclosed in a membrane derived from the host cell, which allows it to enter and infect the cell. This is a common mechanism used by many enveloped viruses to gain entry into their host cells.

Viruses in the extracellular state typically do not possess active enzymes. Enzymes are proteins that catalyze various biochemical reactions, and they are essential for the virus to replicate and carry out its life cycle. However, when a virus is outside of a host cell, it is in an inert state and does not actively carry out any metabolic processes. Therefore, it is true that viruses in the extracellular state possess few, if any, active enzymes.

Virus receptors, which are molecules on the surface of host cells that allow viruses to enter and infect them, are not evenly distributed across the cell surface. Instead, they are often concentrated in specific regions called lipid rafts. These rafts are microdomains within the cell membrane that contain high levels of cholesterol and certain types of lipids. By localizing virus receptors in lipid rafts, the cell can enhance its ability to recognize and interact with viruses, facilitating viral entry and infection. Therefore, the statement "Virus receptors are often not distributed uniformly over the surface of host cells, but are instead concentrated in lipid rafts" is true.

Prions are infectious agents that are composed solely of proteins. They are unique because they do not contain any nucleic acid genome, such as DNA or RNA. This lack of genetic material is what sets prions apart from other infectious agents like viruses or bacteria. Instead, prions are able to replicate and cause disease by inducing a change in the conformation of normal cellular proteins, leading to the formation of abnormal protein aggregates. Therefore, the statement that prions consist of proteins and have no apparent nucleic acid genome is true.

Some of the largest viruses are comparable in size to small bacteria and can be observed using a light microscope. This implies that these viruses are significantly larger than most other viruses, which are typically much smaller and require an electron microscope for visualization.

False. Prions are responsible for causing several human diseases, such as Creutzfeldt-Jakob disease, variant Creutzfeldt-Jakob disease, and fatal familial insomnia. These diseases result from the abnormal folding of normal cellular prion proteins, leading to the accumulation of amyloid plaques in the brain. Prion diseases are characterized by progressive neurological deterioration and ultimately lead to death.

This statement is true because the majority of plant viruses that have been identified and studied are RNA viruses. RNA viruses have RNA as their genetic material instead of DNA. These viruses replicate and infect plants by using the host plant's cellular machinery to produce more viral RNA and proteins. Examples of RNA plant viruses include tobacco mosaic virus, potato virus Y, and cucumber mosaic virus. However, it is important to note that new plant viruses are constantly being discovered, so there may be exceptions to this statement in the future.

Viruses can have either DNA or RNA as their genetic material. Some viruses have DNA as their genetic material, while others have RNA. This genetic material carries the necessary information for the virus to replicate and infect host cells. The choice between DNA and RNA depends on the specific virus and its replication strategy.

Glycoprotein spikes protruding from the outer surface of viral envelopes function as factors that bind to host cells. These spikes have specific receptors that allow them to recognize and attach to specific receptors on the surface of host cells. This attachment is crucial for the virus to enter the host cell and initiate infection. By binding to host cells, these glycoprotein spikes facilitate the entry and subsequent replication of the virus within the host organism.

Animal viruses can be cultivated in suitable host animals, embryonated eggs, and tissue cultures. Cultivating viruses in host animals allows researchers to study the virus in its natural host and observe its effects on the animal. Embryonated eggs provide a controlled environment for virus growth and allow for easy observation of viral effects. Tissue cultures, specifically monolayers of animal cells, provide a more controlled and easily manipulated environment for virus growth and study. Therefore, all of these choices are valid methods for cultivating animal viruses.

All of these options can be used to cultivate plant viruses. Cultures of separated plant cells can be used to grow and infect plant viruses, as the cells provide a controlled environment for viral replication. Whole plants can also be used, where viruses can be introduced through mechanical inoculation or insect vectors. Plant protoplast cultures, which are cells without cell walls, can be infected with viruses and used for viral propagation. Therefore, all of these methods can be utilized to cultivate plant viruses.

Viruses are acellular and cannot be classified as living organisms as they lack the ability to carry out essential life processes on their own. They can exist in both intracellular and extracellular phases, meaning they can be present inside or outside of host cells. Viruses are too small to be observed with a light microscope, but they can be visualized using an electron microscope. Additionally, viruses are known to infect not only animal and plant cells but also a wide range of other organisms, including bacteria and even other viruses.

A complete virus particle is called a virion. A virion refers to the fully formed infectious particle of a virus that is capable of infecting a host cell. It consists of a nucleic acid genome (either DNA or RNA) enclosed in a protein coat called a capsid. The capsid protects the viral genome and helps in the recognition and attachment to host cells. Therefore, the term "virion" accurately describes a fully formed and infectious virus particle.

Prions are of significance because they cause infections in domestic animals and humans. Prions are abnormal proteins that can trigger a chain reaction, causing normal proteins to become misfolded and form aggregates. These aggregates can accumulate in the brain, leading to the development of various neurodegenerative diseases, such as Creutzfeldt-Jakob disease in humans and bovine spongiform encephalopathy (BSE) in cattle. The infectious nature of prions makes them a concern for both animal and human health.

Viral capsid protein subunits are called protomers. Protomers are individual protein units that make up the viral capsid, which is the outer protein coat of a virus. These protomers come together to form the capsid structure and protect the viral genetic material.

The protein coat surrounding the viral genome is called the capsid. The capsid provides protection to the viral genome and helps in the attachment of the virus to host cells. It is composed of repeating protein subunits called capsomeres, which come together to form the overall structure of the capsid. The capsid plays a crucial role in the life cycle of the virus, as it is responsible for protecting the viral genome during transmission and facilitating the release of the genome into host cells during infection.

The statement is false because viruses infecting protists, including algae, have been detected. Viruses are known to infect a wide range of organisms, including protists. There have been numerous studies and reports documenting the presence of viruses infecting protists and algae. Therefore, the statement that viruses infecting protists have never been detected is incorrect.

Hepatitis B virus has been associated with a form of liver cancer. Hepatitis B is a viral infection that affects the liver and can lead to chronic liver disease, including cirrhosis and liver cancer. The virus is transmitted through contact with the blood or other body fluids of an infected person. Chronic infection with hepatitis B virus increases the risk of developing hepatocellular carcinoma, which is the most common type of liver cancer. Therefore, hepatitis B virus is the correct answer in this case.

Enveloped viruses acquire their envelope from the host plasma membrane. This means that the virus takes a piece of the host cell's plasma membrane and incorporates it into its own viral envelope. This allows the virus to evade the immune system and facilitates its entry into new host cells. The viral envelope is important for the virus's ability to infect cells and cause disease.

Viruses do not have a typical cellular structure like other living organisms. Unlike cells, viruses do not have a cellular membrane, organelles, or the ability to carry out metabolic processes on their own. They are considered to be acellular entities that rely on host cells to replicate and carry out their life cycle. Therefore, the statement that viruses have a typical cellular structure is false.

Viral envelopes are composed of proteins, lipids, and carbohydrates. This means that all of the given choices are correct. Proteins, lipids, and carbohydrates are the main components of the viral envelope, which is a protective outer layer surrounding the viral particle. These components play important roles in the structure, function, and interaction of the virus with its host cells.

Hemagglutination refers to the clumping together of red blood cells when they are exposed to a viral suspension. This phenomenon is caused by certain viruses, such as the influenza virus, which have the ability to bind to the surface of red blood cells. The binding of the virus to the red blood cells leads to their aggregation or clumping, which can be observed under a microscope. This process is important in the study of viruses and is used in various laboratory techniques, such as hemagglutination assays, to detect and identify viral infections.

All of the given diseases, scrapie, mad cow disease, kuru, and Creutzfeldt-Jakob Disease, are caused by prions. Prions are misfolded proteins that can induce other proteins to misfold as well, leading to the formation of abnormal protein aggregates in the brain. These aggregates cause progressive and fatal neurodegenerative diseases in animals and humans. Therefore, all of the choices are correct in this case.

Virus morphology refers to the physical characteristics of a virus. It includes aspects such as size, shape, and the presence or absence of an envelope. However, the host range of a virus refers to the range of different organisms that a virus can infect. This is not a physical characteristic of the virus itself, but rather a characteristic of its ability to infect different hosts. Therefore, host range is not included in virus morphology.

Adult T-cell leukemia is caused by retroviruses. Retroviruses are a type of RNA virus that can insert a copy of their genome into the DNA of a host cell. In the case of adult T-cell leukemia, the retrovirus involved is called the human T-cell lymphotropic virus type 1 (HTLV-1). HTLV-1 infects T cells, a type of white blood cell, and can lead to the development of adult T-cell leukemia. This virus is primarily transmitted through sexual contact, blood transfusions, and breastfeeding.

Virion size refers to the size range of viral particles. The correct answer is 10–400 nm. This means that viral particles can vary in size from as small as 10 nanometers to as large as 400 nanometers. Viruses are much smaller than most cells, and their size can vary depending on the specific virus. This size range allows viruses to be small enough to enter and infect host cells, while still containing the genetic material and necessary components for replication and infection.

Self-assembly is the correct answer because it refers to the process in which viral capsids are constructed without any external assistance once the subunits have been synthesized. This means that the subunits come together on their own to form the capsid structure, without the need for any additional factors or facilitators. This process is a characteristic feature of viral capsid assembly.

Viruses replicate through a process called the lytic cycle, not binary fission. In the lytic cycle, the virus attaches to a host cell, injects its genetic material, takes over the host's cellular machinery to produce more viral components, assembles new viruses, and then bursts the host cell to release the newly formed viruses. Binary fission, on the other hand, is a method of cell division used by bacteria and some single-celled organisms. Therefore, the statement "Viruses replicate by binary fission" is not true.

Oncogenes are genes whose expression or abnormal expression causes cancer. These genes play a crucial role in regulating cell growth and division. When oncogenes are activated or mutated, they can promote uncontrolled cell growth and lead to the development of cancer. Understanding oncogenes is important in the field of cancer research and treatment, as targeting these genes can potentially help in developing effective therapies for cancer.

The correct answer is nucleocapsid. In an enveloped virus, the nucleocapsid refers to the part of the virus that includes the nucleic acid genome (such as DNA or RNA) and the surrounding protein coat (capsid). The nucleocapsid is responsible for protecting the viral genome and facilitating its entry into host cells. The envelope, on the other hand, is an outer layer that surrounds the nucleocapsid and is derived from the host cell's membrane.

Human cancer causing viruses most often have a dsDNA genome. This is because dsDNA (double-stranded DNA) is more stable and less prone to mutations compared to other types of genomes such as ssDNA (single-stranded DNA) or RNA genomes. The stability of dsDNA allows the viral genome to be replicated accurately during cell division, reducing the chances of genetic errors that could lead to cancer. Additionally, dsDNA viruses can integrate their genetic material into the host cell's genome, further increasing the risk of cancer development.

The viral protein coat serves a dual purpose. Firstly, it protects the viral genetic material from degradation and damage by external factors such as enzymes and harsh environments. Secondly, it aids in the transfer of the viral genetic material between host cells by facilitating the attachment and entry of the virus into the host cell. Therefore, the correct answer is that the viral protein coat protects the viral genetic material and aids in its transfer between host cells.

Viruses are infectious agents that can only replicate inside the cells of other organisms. The simplest viruses consist of either RNA or DNA enclosed in a protein coat, also known as a capsid. This capsid provides protection for the genetic material and helps the virus to enter host cells. Some viruses may also have a lipid envelope derived from the host cell membrane surrounding the protein coat. However, the presence of enzymes in the virus structure is not necessary for all viruses, making the option of RNA, DNA, and enzymes in a protein coat with a lipid envelope incorrect.

A segmented genome refers to a genome that exists as several separate, nonidentical molecules. These molecules may be packaged together or separately. This means that the genetic material of the organism is divided into different segments or pieces, rather than being present as a single continuous molecule. This arrangement allows for greater flexibility and variation in the genome, as different segments can be rearranged or exchanged.

The correct answer is that a viral DNA genome may have the normal bases found in prokaryotic and eukaryotic DNA, or it may have one or more unusual bases. This means that viral DNA can have the same four nitrogenous bases as found in prokaryotic and eukaryotic DNA, or it can have different bases that are unique to viruses. This flexibility allows viruses to adapt and evolve, making them highly diverse and capable of infecting a wide range of hosts.

Viroids are short infectious single stranded RNAs that can infect some plants. Viroids are not proteins or viruses, but rather small circular RNA molecules that do not code for any proteins. They are able to infect plants and cause various diseases by interfering with the normal functioning of the host plant's cells. Unlike viruses, viroids do not have a protein coat and are composed solely of RNA.