1. The porcelain filter removed diseases from a liquid sample.
2. The porcelain filter removed virions from a liquid sample.
3. The porcelain filter removed bacteria from a liquid sample.
4. The porcelain filter removed a disease from tobacco plants.

1. The development of the light microscope helped scientists discover many viruses of all types of living organisms.
2. The development of the viral receptor helped scientists discover many viruses of all types of living organisms.
3. The development of the porcelain filter helped scientists discover many viruses of all types of living organisms.
4. 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.

1. escapist or the progressive
2. system of self-replication
3. devolution or the regressive
4. virus molecular systematics

1. Scientists can look at fossil records and similar historic evidence.
2. Much about virus origins and evolution remains unknown.
3. Biologists have accumulated a significant amount of knowledge about how viruses originated.
4. 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.

1. capsid
2. virion
3. capsomere
4. viral receptor

1. A virus uses its cellular structure to attach to a host cell.
2. A virus uses a plasma membrane to connect to a host cell.
3. A virus uses matrix proteins to attach to a host cell.
4. Viruses use viral receptors to attach to a host cell.

________ means that the genomic RNA can function as mRNA.

1. Double-stranded
2. Negative polarity
3. Positive polarity
4. 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.

1. human immunodeficiency virus (HIV)
2. rabies (rhabdovirus)
3. canine parvovirus (parvovirus)
4. common cold (picornavirus)

To get a visual look at the internal structure of virions, scientists must use a(n) ________.

1. scanning electron microscope
2. transmission electron microscope
3. porcelain filter
4. light microscope

1. The viral replication cycle does not affect the structure of the host cell.
2. The viral replication cycle cannot affect genetic material of the host cell.
3. The viral replication cycle has seven basic steps.
4. The viral replication cycle can change cell functions or even destroy the host cell.

1. During the budding process, virions leave the host cell individually
2. During the budding process, the host cell bursts.
3. During the budding process, the virus connects with a permissive host cell.
4. During the budding process, the host cell dies immediately.

In the ________ cycle, the virus replicates and bursts out of the host cell.

1. lytic
2. lysogenic
3. cytopathic
4. latency

1. The phage infects a cell in the lytic cycle.
2. The lytic cycle contains the formation of a prophage.
3. In the lytic cycle, new phages are produced; immediately in the lysogenic cycle phage DNA is merged into the host genome.
4. The phages move on to infect other cells in the lysogenic phase.

1. Enveloped viruses and naked viruses both may enter cells using the fusion method.
2. Many enveloped viruses enter the cell by receptor-mediated endocytosis.
3. Naked viruses enter the cell by receptor-mediated endocytosis.
4. 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 ________.

1. cell necrosis
2. discoloration
3. hyperplasia
4. hypoplasia

1. During the release step, genetic information is transferred through the lytic and lysogenic cycles.
2. During the release step, DNA is transcribed to messenger RNA.
3. During the release step, the nucleic acid is released from the viral capsid or envelope.
4. During the release step, the new virions are able to infect adjacent cells and repeat the replication cycle.

1. The HIV virus uses reverse transcriptase to replicate cells and build proteins.
2. The HIV virus uses reverse transcriptase to erase mutated virions.
3. The HIV virus uses reverse transcriptase because it is a retrovirus.
4. The HIV virus uses reverse transcriptase because it has a DNA genome.

1. The herpes simplex virus causes eye infections.
2. The herpes simplex virus causes pneumonia.
3. The herpes simplex virus causes pancreatitis.
4. The herpes simplex virus can cause septicemia.

1. The measles virus causes nasal and lung infections.
2. The measles virus causes pancreas and liver infections.
3. The measles virus causes mouth and gum infections.
4. The measles virus causes brain and skin infections.

1. Vaccines kill viruses.
2. Vaccines stimulate an immune response against future infections.
3. Vaccines inhibit the virus by blocking the action of key viral proteins.
4. Vaccines control and reduce symptoms.

1. phage therapy
2. anti-retroviral
3. gene therapy
4. cancer therapy

1. measles virus
2. norovirus
3. HIV
4. mumps virus

1. Prions are larger than viruses.
2. Prions contain DNA and RNA.
3. The PrPCis the normal form of the protein.
4. The PrPSCis folded abnormally.

Kuru is a prion disease that affects both humans and animals. How is kuru spread?

1. Kuru disease is spread between cattle.
2. Kuru is passed from person to person.
3. Kuru is passed from cows with BSE to humans.
4. Kuru is a viroid that infects plants.

1. Viroids are single-stranded RNA particles.
2. Viroids reproduce only outside of the cell.
3. Viroids produce proteins.
4. Viroids affect both plants and animals.

1. dairy
2. poultry
3. avocado
4. livestock

1. Infected prions cause disease by transmitting nucleic acids to normal prion proteins.
2. Infected prions cause disease by converting DNA to RNA in normal prion proteins.
3. Infected prions cause disease by converting the shapes of normal proteins.
4. Infected prions cause disease by replicating the normal form of the protein.