Title: Viruses
Course: Question Banks

Q: Viral discovery occurred once ________.
- powerful microscopes were developed (Incorrect. Powerful microscopes were not yet available when viruses were discovered.)
- DNA sequencing techniques became routine (Incorrect. Viruses were discovered well before DNA sequencing became routine.)
- a special filtration process was created (Correct. A Chamberland-Pasteur filter was used in the discovery of viruses.)
A: a special filtration process was created

Q: ________ provided evidence that tobacco mosaic disease was not caused by bacteria.
- Adolph Meyer (Incorrect. Meyer showed the tobacco mosaic disease was transferred between plants using liquid plant extracts, indicating it was infectious.)
- Chamberland Pasteur (Incorrect. A Chamberland-Pasteur filter was used in the discovery of viruses, but this is named after two different scientists.)
- Dmitri Ivanowski (Correct. Ivanowski used a special filtration process to show this disease could not be caused by bacteria.)
A: Dmitri Ivanowski

Q: Determining internal structural features of viruses requires ________.
- a special filtration process (Incorrect. A special filtration process was used to identify viruses as the causative agent of tobacco mosaic disease, but does nothing for determining their structure.)
- DNA sequencing (Incorrect. DNA sequencing will not identify internal structures of any kind.)
- transmission electron microscopes (Correct. Viruses are very small so in order to examine internal features of these particles, TEMs must be used.)
A: transmission electron microscopes

Q: Plant pathogens support the ________ hypothesis to explain the origin of viruses.
- devolution (Incorrect. The devolution hypothesis suggests viruses evolved from free-living cells.)
- escapist (Incorrect. The escapist hypothesis is supported by the genome material (RNA or DNA) of a virus.)
- self-replication (Correct. Plant pathogens in particular provide evidence for the self-replication hypothesis.)
A: self-replication

Q: The ________ hypothesis explaining the origin of viruses focuses on viral genetic material.
- devolution (Incorrect. The devolution hypothesis suggests viruses evolved from free-living cells.)
- self-replication (Incorrect. Plant pathogens in particular provide evidence for the self-replication hypothesis.)
- escapist (Correct. The escapist hypothesis is supported by the genetic material (RNA or DNA) of a virus.)
A: escapist

Q: According to the ________ hypothesis, viruses arose from free-living cells but lost many functions during their evolution.
- escapist (Incorrect. The escapist hypothesis is supported by the genome material (RNA or DNA) of a virus.)
- self-replication (Incorrect. Plant pathogens in particular provide evidence for the self-replication hypothesis.)
- devolution (Correct. The devolution hypothesis suggests viruses evolved from free-living cells.)
A: devolution

Q: Many plant viruses are ________.
- enveloped (Incorrect. Animal viruses are usually enveloped.)
- head and tail (Incorrect. Bacterial viruses are usually head and tail viruses.)
- filamentous (Correct. Plant viruses are often filamentous.)
A: filamentous

Q: The most commonly used modern method for classifying viruses is the ________ scheme.
- capsid morphology (Incorrect. While viruses are classified by their capsids, this is not the most common system used.)
- nucleic acid (Incorrect. While viruses are classified by their genomes, this is not the most common system used.)
- Baltimore (Correct. Developed in the 1970s by biologist David Baltimore, the Baltimore scheme is used most often to classify viruses.)
A: Baltimore

Q: Core classification of viruses is based on ________.
- capsid morphology (Incorrect. The capsid is not the “core” of a virus.)
- mRNA production (Incorrect. Viruses cannot produce mRNA.)
- type and structure of nucleic acid (Correct. The genome is the core of a virus, and is the basis of the core classification method.)
A: type and structure of nucleic acid

Q: The ________ divides viruses into seven groups.
- nucleic acid classification scheme (Incorrect. There is no nucleic acid classification scheme for viruses.)
- core classification of viruses (Incorrect. The core classification scheme classifies viruses on multiple factors, not seven different groups.)
- Baltimore classification scheme (Correct. The Baltimore classification scheme places viruses into one of seven groups.)
A: Baltimore classification scheme

Q: Viruses ________ a host cell immediately after attachment.
- uncoat (Incorrect. The next step after viral attachment is not uncoating (or removing the capsid).)
- release (Incorrect. Release is the last stage of a viral attack on a host cell.)
- penetrate (Correct. A virus penetrates a host cell immediately after attaching to the cell.)
A: penetrate

Q: The process of uncoating involves ________.
- unwinding the viral genome (Incorrect. Unwinding the genome occurs after uncoating.)
- removing part of the host’s outer boundary (Incorrect. Some viruses enter their hosts without any damage to the host outer boundary.)
- degrading the viral capsid (Correct. The viral capsid must be removed to release the viral nucleic acid into the host cell for replication.)
A: degrading the viral capsid

Q: ________, like HIV, undergo an extra step in replication before their genome can be copied by the host.
- Complex viruses (Incorrect. There is no “complex” virus group.)
- Venereal viruses (Incorrect. Venereal viruses as a whole do not need to undergo an additional step in replication.)
- Retroviruses (Correct. Retroviruses must convert their RNA genomes into DNA before the host cell can copy that genome.)
A: Retroviruses

Q: ________ viruses are the only animal viruses that utilize fusion to enter a host cell.
- Coated (Incorrect. Coated viruses do not utilize fusion to enter the host.)
- Nonenveloped (Incorrect. Nonenveloped viruses do not utilize fusion to enter the host.)
- Enveloped (Correct. Enveloped viruses enter animal hosts by fusion.)
A: Enveloped

Q: Viral infections that do not cause any symptoms in the host, but that do lead to generation of new virions, are said to be ________.
- chronic (Incorrect. Chronic indicates a long term infection, not the presence or absence of symptoms.)
- intermittent (Incorrect. Intermittent indicates there are some signs of infection but these signs are not always visible.)
- asymptomatic (Correct. An asymptomatic infection has no visible signs of ill effect in a host.)
A: asymptomatic

Q: The process of ________ determines when a lifelong infection of herpes causes temporary lesions on the skin.
- lysogenesis (Incorrect. Lysogenesis is not what causes temporary skin lesions with herpes infections.)
- dormancy (Incorrect. Viruses are not generally described as being “dormant.”)
- latency (Correct. The herpes virus can enter a period of latency, with no symptoms, but at times will become active and result in skin lesions.)
A: latency

Q: ________ transmission of plant viruses occurs between an offspring and parent plant.
- Familial (Incorrect. This is not transmission of a virus from parent to offspring plant.)
- Genetic (Incorrect. This is not transmission of a virus from parent to offspring plant.)
- Vertical (Correct. Vertical transmission of a virus is from a parent to offspring plant.)
A: Vertical

Q: Galls in plants are a result of ________ caused by a viral infection.
- cell necrosis (Incorrect. This is the process by which a virus directly kills plant cells.)
- hypoplasia (Incorrect. Hypoplasia is decreased cell growth and does not result in galls.)
- hyperplasia (Correct. Galls are due to abnormal proliferation, or hyperplasia, of plant cells.)
A: hyperplasia

Q: Often ________ must occur before a virus can enter a plant cell.
- receptor-mediated recognition (Incorrect. Receptor-mediated recognition is more common in animal viruses.)
- genetic mutations (Incorrect. Genetic mutations are not necessary for viruses to enter plant cells.)
- physical damage to cells (Correct. Due to the hard cell wall protecting them, most plant cells must experience physical damage to that wall before a virus can enter.)
A: physical damage to cells

Q: Vaccines prepared from ________ are capable of causing disease in recipients.
- viral pieces (Incorrect. Viral pieces alone are generally incapable of causing diseases, but will trigger an immune response.)
- killed viruses (Incorrect. Killed viruses will not cause diseases in recipients.)
- attenuated viruses (Correct. Weakened viruses are used to prepare some vaccines; despite being weakened, they may still be capable of causing diseases.)
A: attenuated viruses

Q: The most significant danger associated with live viral vaccines is ________.
- mild disease symptoms (Incorrect. This is not the most significant danger with live viral vaccines.)
- immunorejection (Incorrect. Immunorejection will not occur with live viral vaccines.)
- back mutations (Correct. Back mutations can cause a virus to revert to its disease-causing form.)
A: back mutations

Q: Viruses are attenuated to produce vaccines by ________.
- boiling the viruses (Incorrect. This will generally kill viruses, not weaken them.)
- genetically engineering the viral genome (Incorrect. Genetic engineering is used for live viral vaccines but not to attenuate them.)
- growing the viruses under abnormal conditions (Correct. These abnormal conditions weaken, or attenuate, the viruses.)
A: growing the viruses under abnormal conditions

Q: The most successful HIV treatment to date involves ________.
- genetically modifying the viral genome (Incorrect. This is not part of the current treatment approach.)
- novel anti-HIV drugs developed from bacteriophages (Incorrect. This alone is not the most successful HIV treatment to date.)
- a drug cocktail that interferes with multiple stages of the viral lifecycle (Correct. The current treatment approach that works well against HIV interferes with multiple stages of the virus’ lifecycle.)
A: a drug cocktail that interferes with multiple stages of the viral lifecycle

Q: ________ viruses are used as a cancer treatment.
- Bacteriophage (Incorrect. Bacteriophages are used to treat bacterial infections.)
- Adeno- (Incorrect. Adneoviruses are actually used for delivery of genes back into patients during gene therapy.)
- Oncolytic (Correct. Oncolytic viruses specifically attack and kill cancer cells.)
A: Oncolytic

Q: Antiviral drugs generally function to ________.
- destroy viruses directly (Incorrect. Antivirals often cannot destroy viruses.)
- prevent viral infections (Incorrect. Antiviral drugs are not used to prevent viral infections.)
- control and reduce symptoms (Correct. Antivirals generally treat symptoms.)
A: control and reduce symptoms

Q: Prions are unique in that they contain ________.
- no proteins (Incorrect. Prions are made of proteins.)
- triple stranded DNA (Incorrect. Prions do not have triple stranded DNA.)
- no nucleic acids (Correct. Prions are infectious protein particles with no nucleic acids.)
A: no nucleic acids

Q: ________ are responsible for kuru.
- Viroids (Incorrect. Viroids infect plants, not animals. Kuru is a human (animal) disease.)
- Viruses (Incorrect. Viruses do not cause kuru.)
- Prions (Correct. Kuru is a prion disease in some humans of Papua New Guinea)
A: Prions

Q: Prion infections cause ________.
- misfolds in brain tissue (Incorrect. This is not the result of a prion infection.)
- abnormal division of brain cells (Incorrect. This is not the result of a prion infection.)
- lesions in brains (Correct. These holes give rise to spongiform encephalopathies, because the brain takes on a “spongy” appearance.)
A: lesions in brains

Q: ________ are spread by eating infected tissue.
- Viroids (Incorrect. Viroids infect plants only, so eating infected plants would have no impact.)
- Viruses (Incorrect. Some viruses can be spread through infected tissue but not all.)
- Prions (Correct. Prions can be transmitted by eating infected animal tissue.)
A: Prions

Q: Viroids infect ________.
- nervous tissue (Incorrect. Prions infect nervous tissue.)
- bacteria (Incorrect. Viroids do not infect bacteria.)
- plant cells (Correct. Viroids are simpler than viruses but are capable of infecting plant cells.)
A: plant cells

Q: Viroids differ from viruses in that they ________.
- can reproduce independently (Incorrect. Viroids must be reproduced by a host cell.)
- contain both DNA and RNA (Incorrect. Viroids do not contain DNA.)
- do not produce proteins (Correct. Viroids appear to just be infectious RNA particles.)
A: do not produce proteins

Q: ________ have the largest impact on the agriculture industry.
- Prions (Incorrect. To date prions have had a limited impact on livestock; since they only infect animals, they have no impact on the plant side of agriculture.)
- Viruses (Incorrect. Viruses have their largest impact directly on human health.)
- Viroids (Correct. The plants that most viroids infect are agriculture crops like potatoes, cucumbers, and avocados. Some do infect floral plants but not many.)
A: Viroids