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