Chapter 13

In ______-strand RNA viral genomes, the genome functions as an mRNA molecule.

(+)

Viral infections in plants can cause diseases

that are economically devastating

In a lysogenic infection, ______.

the bacteriophage DNA integrates into the host chromosome

Which of the following describes the various viral parts coming together to produce virions?

Assembly

Infection of bacteria by _____ phages always ends with the lysis of the host cell.

Lytic or virulent

In which type of infection does the virus remain in the host for years, sometimes without symptoms?

Persistent

______ infections remain for years, or even the lifetime of the host, sometimes without any symptoms.

Persistent

Reassortment of gene segments that encode viral surface proteins recognized by the immune system can result in a loss of the immune system's ability to recognize and respond to the virus. This phenomenon is called antigenic

Shift

What term is used to describe the transfer of genetic information from one bacterium to another bacterium by a bacteriophage?

Transduction

A(n) ___ is an infectious agent that lacks a capsid and consists only of RNA.

Viroid

Bacteriophages that exit the host cell at the end of an infection by lysing it are called _______ phages.

Virulent

Which of the following are non-cellular infectious agents?

Viruses Viroids Prions

When two different strains of a segmented virus enter the same cell, reassortment of the gene segments can occur, resulting in

antigenic shift

Oncoviruses are viruses that can

cause cancer in humans

Symptoms of acute viral diseases result from

host tissue damage host immune response

Which are the two major categories of viral infections?

1. Acute 2. Persistent

True or false: it is easier to cultivate animal viruses than bacteriophages.

False

Which of the following phage types cause productive infections that do not kill the host cell?

Filamentous

Which of the following about classifying viruses is FALSE?

It is not as important as classifying organisms since they are not living entities.

Viruses that specifically target and kill cancer cells are called _____viruses.

Oncolytic

An infectious agent that consists of protein and no nucleic acid is called a(n)

Prion

Attachment of animal viruses to the host cell typically occurs by means of

Spikes

Bacteriophages play a fundamental role in a type of horizontal gene transfer called

Transduction

Infectious agents that have a simpler structure than viruses include

both viroids and prions

Viral genomes can be

either single-stranded or double-stranded

In the case of animal viruses, the molecules that viral spikes attach to on the host cell in order to gain entry are typically

glycoproteins

The smallest virus is approximately 10 ______ in diameter.

nanometers

Bacteriophages that can enter into a lytic cycle or a lysogenic cycle are called _____ phages

Temperate

Lysogeny is best described as

integration of the viral genome into the host chromosome

Animal viruses can be studied by infecting

live animals cell or tissue culture fertilized chicken eggs

A ______ infection results from the integration of bacteriophage DNA into the chromosome of the bacterial host.

lysogenic

In a(n) ______, viral titer can be determined by counting clear zones in a monolayer of cells

plaque assay

A capsid is

the protein coat that surrounds the viral genome

The nucleocapsid is composed of

DNA or RNA and protein.

Although live animals and fertilized chicken eggs have been used to cultivate animal viruses in the past, these have now been largely replaced by culture.

Cell

Tumors are abnormal growths that result from a malfunction in the regulation of

Cell growth

Mutations in the influenza virus genome can result in minor changes in key viral surface proteins. This type of variation is called antigenic

Drift

______ phages cause productive infections that do not kill the host cell.

Filamentous

Which form of transduction results from packaging errors during phage assembly?

Generalized

__________ transduction is the result of packaging errors during the assembly stage of phage replication.

Generalized

Human cells are larger than viruses by which size factor?

Thousand

An abnormal growth of tissue resulting from a malfunction in the normally highly regulated process of cell growth is a

Tumor

Why are bacteriophages easier to study than animal viruses?

It is easier to grow the bacteriophage host cells in the lab.

Which of the following describe a type of relationship that bacteriophages can have with their host?

Latent infection where host cell genotype is changed Productive lytic infection

Reverse transcriptase is a(n) ______ polymerase.

RNA-dependent DNA

Replicases are ___ polymerases.

RNA-dependent RNA

________ transduction is the result of excision errors made as temperate phages transition from a lysogenic to a lytic cycle.

Specialized

A generalized infection cycle of an animal viruses can be divided into five steps

1. Attachment 2. Genome 3. Synthesis 4. Release

The viral genome is protected from the environment by a protein shell called the

capsid

When an enveloped virus gains entry to an animal cell by fusion, the virus envelope fuses with the

cytoplasmic membrane

Which types of viruses are released by budding?

enveloped viruses

Viruses are best described as

infectious agents

During the process that leads to a lysogenic infection, which of the following inserts the phage DNA into a bacterial chromosome?

integrase

The study of bacteriophages has advanced much faster than investigations on animal viruses in part because

it is easier to grow bacterial cells than animal cells

A prion is best described as ______.

proteinaceous infectious agent

An enzyme that uses an RNA molecule as a template to make a complementary copy of DNA is called

reverse transcriptase

The replication strategy of viruses can be divided into three general categories: those used by

reverse transcribing viruses DNA viruses RNA viruses

In acute viral infections, although the infected host cells may die, the host may survive because

the host's immune system may gradually eliminate the virus

The replication strategies of animal viruses can be divided into three general categories: those used by _________ viruses, _______ viruses, and reverse transcribing viruses.

1. Dna .2 RNA

List the steps of an animal virus infection cycle in the correct order. Start with the earliest at the top.

1. Attachment 2. Penetration and Coating 3. Synthesis of Viral Proteins and replication of the genome 4. Assembly 5. Release

The replication strategies of animal viruses can be divided into three general categories: those used by _______ ____ viruses, viruses, and reverse transcribing viruses.

1. Dna 2. RNA

In a lysogenic infection, the phage DNA that is incorporated into the bacterial host genome is called a

Prophage

This image shows the ______ stage of the T4 phage lytic cycle.

attachment

All of the following are required for synthesis of new virus particles in a host cell EXCEPT

homologous recombination

At minimum, all viruses are composed of

1. nucleic acids 2. proteins

During the ______ or maturation step in viral multiplication, capsids and genetic material are packaged into virions.

Assembly

Replication of temperate phages and lytic phages have which steps in common?

Assembly Biosynthesis of viral components Genome entry Release Attachment

The binding of a bacteriophage surface protein to a host cell receptor is called _____

Attachment

If viruses are present in high enough concentrations in a sample, they can be quantified directly using a(n) _______ microscope.

Electron

Most animal DNA viruses replicate within the host cell's

Nucleus

In animals, replication of most DNA viruses occurs within the host cell's

Nucleus .

Viruses that can cause cancer in humans are known as ______viruses.

Onco

_______are viruses that are capable of infecting and selectively killing cancer cells.

Oncolytic viruses

The stage of viral multiplication at which budding occurs is

Release

The virally encoded polymerase needed for replication of RNA viruses is called a

Replicase

HIV is described as a ______ because it uses reverse transcriptase to make a DNA copy from its RNA genome.

Retrovirus

Viruses that have an RNA genome and use reverse transcriptase to synthesize a DNA copy of that genome are called _

Retroviruses

A _______ is a single virus particle.

Virion

A complete viral particle, which typically consists of nucleic acid surrounded by a protein coat, is called a(n) .

Virion

Which of the following are non-cellular infectious agents composed of only a single-stranded RNA molecule?

Viroids

Which of the following statements about viruses are true?

Viruses contain RNA or DNA but not both. The viral capsid is composed of protein.

Which of the following statements about virus nucleic acid is true?

Viruses contain either DNA or RNA.

Signs of viral infections in plants include ______.

yellowing of leaves stunted growth presence of tumors

Which of the following processes are required for production of virus particles in a host cell?

Transcription of viral genes Replication of viral genome Translation of viral genes

animal viruses

can only be grown in animal cells

The process by which a virus is taken up by a host cell as a result of the host cell's cytoplasmic membrane surrounding the virion to form a vesicle is called

endocytosis

During viral replication, when the genome of a (+) single-stranded RNA virus is used as a template, which of the following is generated?

(-) single-stranded RNA molecules

True or false: There is no need to classify viruses because they are not living organisms.

False

Which form of transduction results from excision errors during the transition from a lysogenic to lytic cycle?

Specialized

The accumulation of mutations in genes that encode viral surface proteins recognized by the immune system results in a type of antigenic variation called

antigenic drift

The major categories of animal viral infections are infections, characterized by the sudden onset of symptoms of a relatively short duration, and infections that can continue with or without symptoms for years.

1. Acute 2. Persistent

A ______ phage can either cause a lytic infection or can incorporate its DNA into the host genome as a prophage.

Temperate