Chapter 6 Viruses, Prions, Microbiology

__________ viruses can infect host cells and later lead to cancer.

oncogenic

Clear, defined patches in a monolayer of cells infected with a virus are called __________, which are essentially a cytopathic effect.

plaques

Which of the following methods can be used to detect viral infections in human patients?

presence of cytopathic effects in tissue sample presence of viral indicator molecules (antigens) PCR of viral nucleic acid identification of antiviral antibodies culturing virus in cell culture

prophage

stage in which the viral DNA is incorporated into the bacterial DNA

Icosahedral

three dimensional, 20-sided capsid with twelve evenly-spaced corners

The primary purposes of viral cultivation include

to isolate and identify viruses in clinical specimens. to research viral structure, multiplication, genetics, and effects on host cells. to prepare viruses for vaccines.

Prions are responsible for

transmissible spongiform encephalopathies. Mad Cow disease. Creutzfeldt-Jakob disease.

The special affinity that a virus has for a particular type of tissue is called a __________.

tropisms

A portion of the viral envelope comes from the cell membrane of the host cell.

true

Enveloped viruses are usually released from the host cell by budding.

true

The hepadnavirus family is so named because viruses within the family infect the liver and possess DNA as their genetic material.

true

The first event to occur is

viral spike proteins are inserted into host cell membrane.

Viruses may be cultured using

-living animals -cultured cells -bird embryos

rapid tests

...Detect virus or cytopathic effects in cells or tissue

cell culture, embryo, animals

...Takes a long time to get diagnosis

lysogenic induction

Activation of prophage in lysogenic cell to begin viral replication

Viruses first appeared on Earth sometime after the rise of eukaryotic organisms.

False

lysogenic conversion

Occurs when a bacterium acquires genes and characteristics from its temperate phage

Which of the following are true about viral envelopes?

They are composed of host membrane. They can contain host-encoded proteins. They can contain virus-encoded proteins. They are important for binding to host cells.

The viral-host relationship is extremely important for pathogenicity, mode of transmission, the immune response, and the human measures used to control viral infections.

True

Which of the following does NOT represent an event in bacteriophage multiplication?

Uncoating of the nucleic acid in cytoplasm

Which step is present in bacteriophage multiplication but not in multiplication of an animal virus?

Viral genetic material is injected into the host cell.

lysogeny

a condition in which the host chromosome carries bacteriophage DNA

Which of the following characteristics are associated with transformed cells?

altered chromosomes changes in cell surface molecules integration of viral DNA into host chromosome

polymerase chain reaction

amplification of viral nucleic acid from a patient sample

The viral capsid

becomes completely enclosed by the region of the cell membrane into which the spikes and matrix protein are embedded.

Enveloped viruses are usually released from the host cell by

budding

Please select criteria that are used to classify viruses.

capsid structure presence/absence of an envelope genetic makeup

helical

capsid with rod-shaped capsomers that bind together to resemble a bracelet

screening

detection via antibodies in the patient's blood

Select all of the statements that are true regarding penetration of animal viruses.

enveloped viruses can penetrate by fusion enveloped viruses can penetrate by endocytosis nonenveloped viruses can penetrate by endocytosis once inside the host, viruses become uncoated

The envelope is entirely formed from viral material.

false

The light microscope was critical in the discovery of viruses.

false

The use of antibiotics is an effective treatment for viral infections.

false

Viral replication follows essentially the same steps as replication of a prokaryotic cell.

false

Viruses are routinely cultured in order to diagnose an infection.

false

Cytopathic changes in virally infected animal cells include

inclusions in the cytoplasm. clumping of cells. cell lysis cytoplasmic inclusions formation of multinucleate syncytia

Viral nucleic acid enters the host cell and uses host cell's replication and synthesis machinery in order to produce new nucleic acid molecules, proteins for the capsid, spikes, and viral enzymes.

TRUE