Chapter 5
Living cells are required for culturing viruses because
1. viruses are technically nonliving. 2. viruses require host cell genetic machinery to replicate. 3. viruses are obligate intracellular parasites
A process of adhering one molecule onto the surface of another molecule.
Adsorption
The step in viral multiplication in which capsids and genetic material are packaged into virions.
Assembly (viral)
The protein covering of a virus's nucleic acid core. Capsids exhibit symmetry due to the regular arrangement of subunits called capsomers.
Capsid
A subunit of the virus capsid shaped as a triangle or disc.
Capsomer
The degenerative changes in cells associated with viral infection.
Cytopathoic Effect
Identify the individual/s responsible for demonstrating that a disease in tobacco was caused by a virus
D. Ivanovski and M. Beijerinck
The process whereby solid and liquid materials are taken into the cell through membrane invagination and engulfment into a vesicle.
Endocytosis
A virus whose nucleocapsid is enclosed by a membrane derived in part from the host cell. It usually contains exposed glycoprotein spikes specific for the virus
Enveloped Virus
True or False: A viral envelope is constructed from identical subunits called capsomeres
False
True or False: Animal viruses can cause acute infections or can persist in host tissues as lytic infections that can reactivate periodically throughout the host's life.
False
The complete set of chromosomes and genes in an organism.
Genome
Type of host range or group of hosts that a given virus can successfully invade
Host Range
The process whereby a bacteriophage in the prophage state is activated and enters the lytic cycle.
Induction
Who postulated the idea that there are "living things" smaller than bacteria (that were not able to be filtered out of solution), and proposed the term "virus"?
Louis Pasteur
The physical rupture or deterioration of a cell
Lysis
A bacterium acquires a new genetic trait due to the presence of genetic material from an injecting phage
Lysogenic Conversion
The persistence of bacteriophage DNA in a host without producing virions or lysing the bacterial host cell.
Lysogeny
A viral cycle that causes the physical rupture of the cell as viral particles are released
Lytic
In viruses, the close physical combination of the nucleic acid with its protective covering
Nucleocapsid
Mammalian virus capable of causing malignant tumors
Oncovirus
The step in viral multiplication in which the virus enters the host cell.
Penetration
In virus propagation methods, the clear zone of lysed cells in tissue culture or chick embryo membrane that corresponds to the area containing viruses.
Plaque
A cytopathic protein associated with the slow-virus spongiform encephalopathies of humans and animals.
Prion
A lysogenized bacteriophage; a phage that is latently incorporated into the host chromosome.
Prophage
The genome of a virus when it is integrated into a host cell's DNA.
Provirus
The step in viral replication in which new virions leave the host cell.
Release (viral)
A multinucleated mass formed by the joining of individual cells.
Syncytium
The step in viral multiplication in which viral genetic material and proteins are made through replication and transcription/translation.
Synthesis (viral)
A bacteriophage that enters into a less virulent state by becoming incorporated into the host genome as a prophage instead of in the lytic form that destroys the cell.
Temperate (lysogenic) phage
The classification/identification system in the text uses this sequence of characteristics to group viruses
The classification/identification system in the text uses this sequence of characteristics to group viruses
In microbial genetics, the transfer of genetic material contained in "naked" DNA fragments from a donor cell to a competent recipient cell.
Transformation
True or False: In penetration by endocytosis, the entire virus is engulfed by the cell and enclosed in a vacuole or vesicle.
True
True or False: The largest virus is bigger than the smallest bacterium.
True
True or False: The two major types of viruses are DNA and RNA viruses.
True
True or False: Viral infections are difficult to treat because the drugs that attack viral replication also cause serious side effects in the host.
True
True or False: Viruses can be harmless or even beneficial
True
True or False: Viruses that alter host genetic material may cause oncogenic effects.
True
The release of nucleic acid from the capsid of a virion that has entered an animal cell.
Uncoated
The process of removal of the viral coat and release of the viral genome by its newly invaded host cell.
Uncoating
The nucleic acid core surrounded by a capsid, which may be enclosed in an envelope.
Virion
An infectious agent that, unlike a virion, lacks a capsid and consists of a closed circular RNA molecule.
Viroid
Microscopic, acellular agent composed of nucleic acid surrounded by a protein coat.
Virus
Identify the proper order of phases in the life cycle of animal viruses:
adsorption, penetration, uncoating, synthesis, assembly, and release
Spikes are essential for the
attachment of viruses to the host cell.
Viruses differ from cells in that viruses
contain DNA or RNA, but not both.
Viruses can cause damage to infected cells, such as physical damage (e.g. lysis), nuclear inclusions, cytoplasmic inclusions, clumping, etc. These are termed
cytopathic effects.
Viruses are best viewed by
electron microscopy
The term Poxviridae indicates that we are looking at a virus
family
Enveloped viruses include
herpes virus.
The main criteria presently used for grouping viruses does NOT include
host infected
Identify the viral disease from the list below: botulism influenza anthrax ringworm
influenza
A naked virus exits a cell by ________; an enveloped virus exits a cell by ________.
lysis, budding off
The disease bovine spongiform encephalopathy is also known as
mad cow disease
Viruses completely lack the genes for synthesis of
metabolic enzymes.
Structurally, the simplest virus is a/n
naked virus
The central core of a virus particle consists of
nucleic acid.
One way to detect the growth of a virus in culture is to observe the degeneration and lysis of infected cells in the monolayer of cells. These areas show up as clear, well-defined patches in the cell sheet called
plaques.
Spongiform encephalopathies are thought to be caused by
prions.
A viral capsid is composed of
proteins.
Which of the following is NOT one of the primary purposes of viral cultivation?
to classify viruses for taxonomic reasons
