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chapter 13

protection and recognition

The outermost layer of a virion fulfills what functions of the virus?

nucleic acid

During the intracellular state, a virus exists as

type of nucleic acid

Viruses are primarily classified according to their

interactions

Host specificity of a virus is due to

envelope

What would NOT be found as a component of a bacteriophage?

in both cells and viruses

A lipid membrane is present

both cells and viruses

Double-stranded DNA genomes are found in

cells only

Cytoplasm is a characteristic of

true

Most viruses cannot be seen by light microscopy. TRUE OR FALSE

true

Protozoa are susceptible to viral attack. TRUE OR FALSE

they require a host to reproduce

How are viruses different from cells?

package and protect the viral genome

What is the function of the structural elements of a virus?

a prophage

Lysogenic viral DNA integrating into the host genome is referred to as

exposure to UV light

what event might trigger induction of a temperate bacteriophage?

host cell dies during lytic stage

How is the lytic cycle different from the lysogenic cycle with respect to the infected host cell?

copied every time the host DNA replicates

What is the fate of the prophage during the lysogenic stage?

penetration

In which stage is the viral DNA introduced into the cell?

assembly

In which stage does formation of mature viruses occur?

biosynthesis

The host DNA is usually degraded during which stage?

virus would not infect the new host

What would be the fate of a lytic bacteriophage if the host cell died prior to the assembly stage?

lysogenic conversion

Bacteriophage genes that cause toxin production in a normally harmless bacterial species are an example of _____.

the infected cell may live for a long time

Infections with enveloped animal viruses are similar to lysogenic phage infections because _____.

entry and release

Lysozyme is important for which of the following stages of lytic replication in bacteriophage T4?

UV light and X rays

What agent is capable of inducing conversion of a prophage back to a lytic phage?

prusiner

Which of the following individuals discovered prions?

virion

what is a virus in the extracellular state?

plant

The first virus to be identified was isolated from a _____.

protein

The capsid of a virus is made out of which of the following types of molecules?

prion

does NOT refer to viral shapes

dependent on host cell

Why do viruses have to infect host cells?

attachment

The tail fibers of a bacteriophage are most useful during which of the following stages of the lytic replication cycle?

viral DNA

Which of the following is a major difference between a lysogenic and a lytic cycle in bacteriophages?

retroviruses

What viruse creates a DNA intermediary molecule from the information in their RNA genomes?

herpesviruses

What types of viruse replicates in the cell's nucleus?

rna dependent

What type of viruses replicates in the cell's nucleus?

cytoplasmic membrane

Bacteriophages can use all of the following structures for attachment to a bacterial cell EXCEPT _____.

envelope

A naked virus is one without _____.

uncoating

Each of the following features is common to BOTH bacteriophage AND animal virus infections EXCEPT __________.

phage persists

Each of the following features is common to BOTH bacteriophage AND animal virus infections EXCEPT __________.

cancer causing viruses

In the early 1900s, the virologist F. Peyton Rous discovered _____.

allow bacteriophages to become latent

Fertilized chicken eggs are useful for the culture of viruses for all of the following reasons EXCEPT _____.

continuous

HeLa cells are an example of a __________ cell culture.

contain no nucleic acid

Scientists have determined that prion diseases are not caused by a type of slow virus because prions _____.

true

Viruses have genomes of DNA or RNA, but never both. TRUE OR FALSE

true

Viruses can specifically infect one type of cell within an organism. TRUE OR FALSE

true

Bacteriophages outnumber all known life forms. TRUE OR FALSE

false

According to the ICTV scheme of classification, viruses can be classified by a variety of characteristics, including the diseases they cause. TRUE OR FALSE

true

Proviruses become a permanent part of the host cell's genome. TRUE OR FALSE

true

Bacteriophages can be used in place of antibiotics to treat certain bacterial diseases. TRUE OR FALSE

true

Lysogenic bacteriophages can be excised from the chromosome by any agent that damages the cell's DNA. TRUE OR FALSE

false

Retroviruses need RNA-dependent RNA transcriptase to replicate themselves. TRUE OR FALSE

false

Diploid cell cultures have an unlimited life span. TRUE OR FALSE

false

The destruction of chickens and other domesticated fowl prevents the spread of avian influenza. TRUE OR FALSE

false

An infection in which a host cell sheds new viruses slowly and steadily is called a latent infection. TRUE OR FALSE

spongiform encephalopathies

As a group, prion diseases are more formally known as _____.

true

An icosahedral capsid is the most common type of polyhedral capsid and is also found in bacteriophage. TRUE OR FALSE

viroids

Small, circular RNA molecules that are infectious to plants are called _____.

false

Viruses are classified into kingdoms and divisions, just like bacteria and eukaryotes.

induction

A prophage is excised from the host chromosome and viral replication proceeds in a process called _____.

false

The viral envelope contains phospholipids and proteins, all of which originate from the host membrane.

assembly

Which step in the viral life cycle is usually a spontaneous process, but is sometimes controlled by viral enzymes?

false

If neoplasia occurs, this means that cancer will follow. TRUE OR FALSE

host membrane merges

What is the main difference between membrane fusion and endocytosis?

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