Assessment 13

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

electron

Lysogeny is best described as ______.

integration of the viral genome into the host chromosome

Enveloped viruses have an outer layer made up of _______.

lipid

Animal viruses can be studied by infecting ______.

live animals fertilized chicken eggs cell or tissue culture

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

lysogenic

Productive infection

new viral particles are produced

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

oncolytic viruses

DNA viruses often encode their own DNA ________ for DNA synthesis, which allows them to replicate even if the host cell is not actively duplicating its own chromosome.

polymerase

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

DNA RNA

The nucleocapsid is composed of ______.

DNA or RNA and protein.

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

specialized

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

spikes

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

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

- translation of viral genes - replication of viral genome - transcription of viral genes

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

cytoplasmic membrane

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

integrase

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

persistent

A capsid is ______.

protein coat that surrounds the viral genome

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

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

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

Biosynthesis of viral components Release Genome entry Attachment Assembly

Reverse transcriptase is a(n) ______ polymerase.

RNA-dependent DNA

Replicases are ______ polymerases.

RNA-dependent RNA

The enzyme of RNA viruses that typically lacks proofreading ability and thus makes many mistakes compared to the polymerases of DNA viruses is ______.

Replicaste

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

Reverse transcribing viruses, DNA viruses, RNA viruses

Phage DNA and proteins are made during the ________ step of the T4 lytic cycle.

Synthesis

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

attachment

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

drift

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

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

filamentous

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

generalized

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

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

nucleus

Most animal DNA viruses replicate within the host cell's ______.

nucleus

Viruses that can cause cancer in humans are known as _______ viruses.

oncogenic

Viruses that specifically target and kill cancer cells are called ______ viruses.

oncolytic

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

persistent

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

plaque assay

RNA viruses have a higher mutation rate than DNA viruses because replicases typically lack ______ ability.

proofreading

RNA viruses have a higher mutation rate than DNA viruses because replicases typically lack _______ ability.

proofreading

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

retroviruses

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

reverse transcriptase

Many animal viruses have proteins called ________ that attach to receptors on host cells.

spikes

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

temperate

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

temperate

In a lysogenic infection, ______.

the bacteriophage DNA integrates into the host chromosome

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

tumor

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

virion

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

virulent

The enzyme of RNA viruses that typically lacks proofreading ability and thus makes many mistakes compared to the polymerases of DNA viruses is ______.

Replicase

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

Which types of viruses are released by budding?

enveloped viruses

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

prophage

The stage of viral multiplication at which budding occurs is ______.

release

The viral proteins that stick out from either the lipid bilayer of enveloped viruses or the capsid of non-enveloped viruses, and attach to host cells, are ______.

spikes

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

specialized

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

retrovirus

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

replicase

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

Naked viruses do not have an outer lipid bilayer. These viruses are called _______-________ viruses.

non-enveloped

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

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

(+)

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 uncoating 3. synthesis of viral proteins and replication of the genome 4. assembly 5. release

A generalized infection cycle of an animal viruses can be divided into five steps: 1. ______; 2. ______ entry; 3. _______; 4. ________; and 5. _______.

Attachment Genome Synthesis Assembly Release

True or false: DNA viruses can only replicate when the host cell is replicating its own genome.

False

True or false: Lysogens are more susceptible to reinfection by the same type of phage.

False

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

False

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

Filamentous, M13, Temperate, or Lysogenic

Why are bacteriophages easier to study than animal viruses?

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

Latent state

Viral genome remains silent within the cell

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

Viruses contain either DNA or RNA

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

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

antigenic shift

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

assembly

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

assembly

All of the following are required for synthesis of new virus particles in a host cell EXCEPT ______. RNA synthesis homologous recombination protein synthesis genome replication

homologous recombination

Symptoms of acute viral diseases result from ______.

host immune response host tissue damage

Which of the following describes a consequence of lysogeny that could result in human disease?

lysogenic conversion

______ is a change in the phenotype of a lysogen as a consequence of the specific prophage it carries.

lysogenic conversion

Consequences of lysogeny include ______.

lysogenic conversion immunity to superinfection

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

lytic, virulent, or T4

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

transduction

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

transduction

Which of the following about classifying viruses is FALSE?

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

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

false; animal viruses need animals or animal cells for cultivation

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

generalized

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.

acute and persistent

How does bacteriophage nucleic acid enter the host cell?

injection

Which are the two major categories of viral infections?

acute and persistent