Viruses were first discovered after the development of the porcelain filter, called the Chamberland-Pasteur filter. How did the porcelain filter enable scientists to discover viruses?
- The porcelain filter removed diseases from a liquid sample.
- The porcelain filter removed virions from a liquid sample.
- The porcelain filter removed bacteria from a liquid sample.
- The porcelain filter removed a disease from tobacco plants.
In the late 1930s, scientists got their first good view of viruses. How did this happen?
- The development of the light microscope helped scientists discover many viruses of all types of living organisms.
- The development of the viral receptor helped scientists discover many viruses of all types of living organisms.
- The development of the porcelain filter helped scientists discover many viruses of all types of living organisms.
- The development of the electron microscope helped scientists discover many viruses of all types of living organisms.
Determining the origins of viruses is challenging. The _____ hypothesis proposes to explain the origin of viruses by suggesting that viruses evolved from free-living cells.
- escapist or the progressive
- system of self-replication
- devolution or the regressive
- virus molecular systematics
Which statement best describes what biologists know about the evolution of viruses?
- Scientists can look at fossil records and similar historic evidence.
- Much about virus origins and evolution remains unknown.
- Biologists have accumulated a significant amount of knowledge about how viruses originated.
- Biologists know exactly when viruses emerged and from where they came.
A(n) _____ is an individual virus particle outside a host cell that consists of a nucleic acid core, an outer protein coating, and sometimes an outer envelope.
- viral receptor
For many viruses to penetrate the cell membrane and complete their replication inside the cell, the virus must attach to their host cells. Describe how a virus attaches to a host cell.
- A virus uses its cellular structure to attach to a host cell.
- A virus uses a plasma membrane to connect to a host cell.
- A virus uses matrix proteins to attach to a host cell.
- Viruses use viral receptors to attach to a host cell.
_____ means that the genomic RNA can function as mRNA.
- negative polarity
- positive polarity
- replica intermediates
Viruses are often classified based on the type of genetic material and its structure. In the Baltimore classification scheme, the _____ virus has a single-stranded RNA (–) genome.
- human immunodeficiency virus (HIV)
- rabies (rhabdovirus)
- canine parvovirus (parvovirus)
- common cold (pircornavirus)
To get a visual look at the internal structure of virions, scientists must use a(n) ____.
- scanning electron microscope
- transmission electron microscope
- porcelain filter
- light microscope
Which of the following statements about the viral replication cycle is accurate?
- The viral replication cycle does not affect the structure of the host cell.
- The viral replication cycle cannot affect genetic material of the host cell.
- The viral replication cycle has seven basic steps.
- The viral replication cycle can change cell functions or even destroy the host cell.
What happens in the replication cycle?
- During the budding process, virions leave the host cell individually
- During the budding process, the host cell bursts.
- During the budding process, the virus connects with a permissive host cell.
- During the budding process, the host cell dies immediately.
In the _____ cycle, the virus replicates and bursts out of the host cell.
How is the lytic cycle different from the lysogenic cycle?
- The phage infects a cell in the lytic cycle.
- The lytic cycle contains the formation of a prophage.
- In the lytic cycle, new phages are produced; immediately in the lysogenic cycle phage DNA is merged into the host genome.
- The phages move on to infect other cells in the lysogenic phase.
Which of the following statements is false?
- Enveloped viruses and naked viruses both may enter cells using the fusion method.
- Many enveloped viruses enter the cell by receptor-mediated endocytosis.
- Naked viruses enter the cell by receptor-mediated endocytosis.
- Undergoing shape changes and creating channels in the host cell membrane is an alternative method of cell penetration used by naked viruses.
An apple tree has yellow splotches on the leaves. This is a symptom of _____.
- cell necrosis
What happens during the release step in the viral replication cycle?
- During the release step, genetic information is transferred through the lytic and lysogenic cycles.
- During the release step, DNA is transcribed to messenger RNA.
- During the release step, the nucleic acid is released from the viral capsid or envelope.
- During the release step, the new virions are able to infect adjacent cells and repeat the replication cycle.
Why does the HIV virus use reverse transcriptase in the replication process?
- The HIV virus uses reverse transcriptase to replicate cells and build proteins.
- The HIV virus uses reverse transcriptase to erase mutated virions.
- The HIV virus uses reverse transcriptase because it is a retrovirus.
- The HIV virus uses reverse transcriptase because it has a DNA genome.
What are the symptoms of the herpes simplex virus?
- The herpes simplex virus causes eye infections.
- The herpes simplex virus causes pneumonia.
- The herpes simplex virus causes pancreatitis.
- The herpes simplex virus can cause septicemia.
Which of the following statements accurately describes the measles virus?
- The measles virus causes nasal and lung infections.
- The measles virus causes pancreas and liver infections.
- The measles virus causes mouth and gum infections.
- The measles virus causes brain and skin infections.
Which of the following statements best describes vaccines?
- Vaccines kill viruses.
- Vaccines stimulate an immune response against future infections.
- Vaccines inhibit the virus by blocking the action of key viral proteins.
- Vaccines control and reduce symptoms.
Which kind of therapy attacks a stage of the virus replicative cycle?
- phage therapy
- gene therapy
- cancer therapy
Which virus causes parotitis?
- measles virus
- mumps virus
Which of the following statements about prions is true?
- Prions are larger than viruses.
- Prions contain DNA and RNA.
- The PrPCis the normal form of the protein.
- The PrPSCis folded abnormally.
Kuru is a prion disease that affects both humans and animals. How is Kuru spread?
- Kuru disease is spread between cattle.
- Kuru is passed from person to person.
- Kuru is passed from cows with BSE to humans.
- Kuru is a viroid that infects plants.
Which of the following statements about viroids is true?
- Viroids are single-stranded RNA particles.
- Viroids reproduce only outside of the cell.
- Viroids produce proteins.
- Viroids affect both plants and animals.
On which industry can viroids have a severe impact?
Which of the following statements best explains how infected prions cause disease?
- Infected prions cause disease by transmitting nucleic acids to normal prion proteins.
- Infected prions cause disease by converting DNA to RNA in normal prion proteins.
- Infected prions cause disease by converting the shapes of normal proteins.
- Infected prions cause disease by replicating the normal form of the protein.