Microbiology Chapter 13

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The family to which the Rhinovirus belongs is the

Picornaviridae.

What part of the E. coli T4 phage attaches to the host cell receptors?

Protein fibers at the end of the phage tail.

Crystallization of Tobacco Mosaic Virus was accomplished by

Stanley

One of the most intensively studied virulent phages which infects E. coli is

The integration of phage DNA into host DNA occurs in much the same fashion as seen in transformation, transduction or conjugation. (t/f)

True

The restriction-modification system always has two genes involved, the cutting enzyme and the methylating enzyme. (t/f)

True

Transduction often involves defective virus. (t/f)

True

Virulent as well as temperate phages can serve as generalized transducing phages. (t/f)

True

Viruses that cause acute infection result in productive infections. (t/f)

True

non enveloped and enveloped viruses both may enter the host via endocytosis. (t/f)

True

The site at which a virus has infected and subsequently lysed the infected cell, releasing its progeny to infect and lyse surrounding cells, thereby forming a "clear zone", is referred to as

a plaque.

Transducing virulent phages do not lyse the cells they invade because

bacterial DNA has replaced critical viral DNA in the phage.

Viruses that infect bacteria are referred to as

bacteroiphages

Viruses may not be cultivated in

blood agar

In addition to lysis, animal viruses may exit the host cell by

budding

The shape of the virus is determined by its

capsid

Bacteria infected with filamentous phages are termed

carrier cells

Once integrated, phage DNA can remain in the prophage state as long as

certain phage genes are repressed.

Phage-encoded proteins are

coded for by phage DNA AND early proteins.

The activation of the SOS system in a bacterium infected with a prophage results in

complete lysis of the bacterial culture AND destruction of the viral repressor through host protease activity.

A virion is a(n)

complete, extracellular virus particle.

The changes that occur in virally-infected cells are characteristic for a particular virus and are referred to as the

cytopathic effect.

If the infecting phage lacks some critical pieces of DNA necessary for replication it is called

defective

Bacteriophages and animal viruses

differ because bacteriophages leave the capsid outside the cell, while animal virus entry involves the entry of the whole nucleocapsid.

Viruses are commonly referred to by their _________ name.

disease AND species

The common species name of the virus is based on the

disease the virus causes

The replicative form of nucleic acid in filamentous phages is

dsDNA.

If reasonably pure preparations of virus are available, the number of virus present may be determined by

electron microscopy.

When an enveloped virus adsorbs to the host cell with its protein spikes, the virions are taken into the cell by the process of

endocytosis

The viral envelope closely resembles the .

eukaryotic cell membrane.

An exit method used by viruses which does not immediately destroy the host bacterium is

extrusion

What are two ways that phage can replicate in harmony (not directly lysing) their host cell?

extrusion and lysogeny

The bacterial viruses that are released by a process termed extrusion are called

filamentous phages.

The enveloped viruses typically obtain their envelope

from the host plasma membrane AND as they exit the host.

Cells infected with animal viruses lyse because

functions necessary for cell survival are not carried out and the cell dies.

The receptors to which animal virus attachment proteins usually bind are

glycoproteins

Enveloped viruses

have an outer lipid bilayer membrane containing various proteins.

The best known chronic infection involves

hepatitis B.

The best-known examples of viruses that cause latent infections are

herpes AND chickenpox

Specialized transduction

involves the transfer of a few specific genes, utilizes a defective virus AND only involves genes near the viral DNA integration site.

The protein coat of a virus

is called a capsid, protects the nucleic acid AND is involved in recognition of host cell receptors.

Resistance of some animals to certain viral diseases is based on

lack of specific receptors on the host cell.

The phenomenon responsible for the ability of Corynebacterium diphtherium to produce the virulent toxin responsible for the devastating effects of diphtheria is called

lysogenic conversion

Phages that can either replicate and cause cell lysis or can integrate their DNA into the host DNA are called

lysogenic phages.

In the region of budding, the inside of the plasma membrane becomes coated with .

matrix proteins

A temperate phage

may be lysogenic AND enters a lysogenic or lytic life cycle shortly after entering the host cell.

Cells taken from a tumor

may be used to grow viruses AND can be cultivated in vitro indefinitely.

The term "segmented" refers to viruses that

may contain several pieces of RNA.

Carriers

may have a persistent infection AND may be a source of infection.

Assembly of the T4 phage

may involve some self-assembly AND may involve the use of scaffolds

Outside of living cells, viruses are

metabolically inert.

DNA is protected from restriction enzymes by being

methylated

Prions affect the

nervous system

Using phages to treat a bacterial infection is an interesting idea because

of the increasing problem of antibiotic resistance.

Filamentous phage

only infect E. coli that have pili.

In latent infections, the virions are

only produced during reactivation

One group of animal viruses that are able to agglutinate red blood cells are the

orthomyxovirus

An infection in which the virus is continually present in the body is referred to as

persistent

Viroids cause disease in

plants

A limiting factor for viral infection is

presence of specific receptor molecules on the host cell.

Normal tissue taken from animals and prepared immediately as media for viral growth is termed a(n)

primary culture

Viruses

probably keep the numbers of bacteria in check AND are active in passing DNA from one bacterium to another.

Phage-encoded enzymes are

produced in a sequential manner AND used to customize the cell for viral production.

A virion is composed of .

protein, either RNA or DNA, and possibly lipid.

The approximate viral concentration of a sample may be determined by

quantal assay

During attachment of phage to E. coli, the phage

randomly bump into the bacteria AND attach to proteins or carbohydrates on the bacterial surface.

For which of the following processes are enzymes not required?

self-assembly

A key feature of all viral infections is the

separation of viral nucleic acid from the capsid.

There are _______ families of DNA containing viruses that infect vertebrates.

seven

The terms helical, icosahedral and complex refer to

shape of viruses

Animal viruses are divided into a number of families whose names end in

-viridae.

In the case of T-even phages, the burst size is about

200 per host cell.

The time from absorption to release for T-even phage is about

30 minutes

What is a defective phage?

A virus that has lost some of its genetic material, and therefore cannot replicate within a new target cell.

Prions replicate by converting normal host proteins into prion proteins. responsible for "Mad Cow Disease" can cause a similar disease in humans. can be transmitted by consumption of dried or cooked food. that cause Spongiform Encephalopathy have the same amino acids but different folding properties from PrPc.

All of the above

Transmission of plant viruses by insects can occur from viruses associated with insect mouth parts. viruses circulating but not multiplying in the insect's body. viruses that multiply within the body of the insect. All of the above

All of the above

Most phages that contain single-stranded DNA are extruded. contain a positive-sense DNA strand. have their DNA transformed to double-stranded DNA before replication and transcription occur.