Ch 6

Which of the following describes viral DNA genomes?

Either single or double-stranded

Which of the following describes viral RNA genomes?

Either single-stranded or double-stranded

Which type of microscope is usually used to examine viruses?

Electron

Which of these terms does not belong in this group?

Embryonic culture

Which term is used to describe the process in which a virus is engulfed by a cell in a vacuole or vesicle?

Endocytosis

It is believed that much of the viral DNA present in human DNA has come from which of the following?

Endogenous retroviruses

Many animal viruses will acquire which of the following from the host cell's membrane?

Envelope

Which of the following viruses has the longest multiplication cycle?

Herpesviruses

Which of the following is a term used to describe the different host cells which a virus can infect?

Host range

The length of a viral multiplication cycle is usually measured in which of the following units?

Hours

Different viruses can infect which of the following?

Human, bacterial, or plant cells

What term is used to describe the capsid of a virus which has 20 equally spaced panels of capsomers forming a symmetrical structure?

Icosahedral

Which Latin phrase describes the cultivation or testing "in glass" or outside of a living organism?

In vitro

Using laboratory animals for experimentation is considered which of the following?

In vivo

When viruses are exposed to compounds or UV-light which make them non-infectious what are they called?

Inactive

What term is used to define the process of a prophage being activated and entering into the lytic cycle?

Induction

Lysogeny is best described as which of the following?

Integration of the viral genome into the host chromosome

Which is a naturally produced antiviral protein in humans?

Interferon

_____ are natural antiviral proteins produced in humans that have shown some potential for prevention of viral infection and cancer treatment.

Interferons

Which 2 scientists are credited with discovering the tobacco mosaic virus?

Ivanovski and Beijerinck

Some animal viruses can insert their genomes into a host cell's DNA. This process is called which of the following?

Latency

Which describes the number of vaccines available against viral infections?

Limited number of vaccines

The discovery of the light microscope had what type of impact on the observation of viruses?

Little to none

During the lytic cycle of bacteriophages, the ultimate destiny of a phage-infected bacterial cell is which of the following?

Lysis

Naked viruses are released from animal cells by which of the following methods?

Lysis

When a bacterium acquires a new trait from a temperate phage, which of the following has occurred?

Lysogenic conversion

_____ is the persistence of bacteriophage DNA within a host chromosome.

Lysogeny, Latency, or Prophage

Which scientist proposed the term "virus"?

Martinus Beijerinck

The term "naked" used in describing viruses implies which of the following?

No lipid envelope

If a virus were to infect a host cell but the cell's enzymes had been denatured, could the virus still replicate?

No, because the virus relies on host enzymes and machinery.

Which of the following describes viruses?

Non-living, infectious agent

Where are most DNA viruses replicated and assembled within the host?

Nucleus

What term is used to describe viruses that can cause cancers?

Oncogenic

Bacteriophages infect which of the following?

Only bacteria cells

Which of the following tests can detect and amplify minute amounts of viral nucleic acid in a sample?

PCR

Which of the following terms describes viruses in the carrier state within the host cells?

Persistent infections

Which of the following describes a "clear" area where a phage-infected cell lysed and infected all of the other cells and lysed them?

Plaque

Which of the following is a group of complex viruses that lack a typical capsid and are covered by a dense layer of lipoproteins and fibrils?

Poxviruses

_____ cell culture is the type of tissue culture used when freshly isolated animal tissue is placed in a growth medium.

Primary

Freshly isolated animal tissue in a growth medium is called which of the following?

Primary cell culture

Which of the following is used to describe the phage DNA that is latently incorporated into the bacterial host genome?

Prophage

What is the primary function of the viral capsid and envelope?

Protection

Prions are composed of what molecule?

Protein

Which of the following best describes a prion?

Proteinaceous-infectious agent

Bullet-shaped enveloped viruses are known as which of the following?

Rhabdoviruses

Which describes most viral infections?

Self-limiting

Which of the following viral structures must be specific for adsorption?

Spike proteins

Which best describes the shape of a helical virus?

Spiral

What is the purpose of vaccines?

Stimulate host immune system

Viruses are classified into families based on genetic makeup and which of the following?

Structure

Which is not a reason that eggs provide an excellent in vivo viral cultivation system?

The egg contains a tissue monolayer.

Compare the size of mimiviruses and pandorviruses to an average-sized virus.

They are 20-50 times larger.

It is possible for a lysogenized bacteria to produce which of the following that are harmful to people?

Toxins

Genes for toxin production and drug resistance can be transferred by bacteriophages between bacteria during which process?

Transduction

Which term describes the integration of an oncogenic virus into mammalian DNA, changing the characteristics of the host cell?

Transformation

Which term describes the tissue specificities of animal viruses for certain body cells?

Tropisms

True or false: It is common for some antiviral drugs to have negative side effects in people because the drugs target host cell metabolic functions.

True

True or false: It is possible for a bacterial cell infected with a temperate phage to replicate before induction occurs.

True

True or false: Most viral infections do not result in death of the host organism.

True

True or false: Prions are resistant to high temperatures.

True

True or false: The number of viruses released by an infected host cell can vary in the thousands.

True

True or false: Virus cultivation is an important skill because viral stocks are needed for vaccines.

True

Who discovered bacteriophages in 1915?

Twort and d'Herelle

Which term best describes viruses?

Ultramicroscopic

Which is false regarding the viral envelope and the membrane of its host?

Viral glycoproteins are present in the host membrane but not in the viral envelope.

The viral envelope is compositionally different from a non-infected host cell because of the presence of which of the following?

Viral proteins

Which is most important for attachment of a virus to a host cell?

Viral specificity for host receptors

Which of the following is composed of only RNA?

Viroid

Which of the following generally carries the least amount of genetic material?

Virus

The word _____ is Latin for poison and refers to a particular group of pathogens.

Virus or Virion

Which of the following enables some viruses to propagate better in a particular animal compared to others?

Virus-specific animal receptors

Which type of microbe is considered the most abundant on earth?

Viruses

Which of the following best explains why viruses have so few genes?

Viruses do not have metabolic pathways.

What does "obligate" mean in regard to viruses?

Viruses must have a host cell.

The two main processes by which viruses penetrate host cells are engulfment, also known as _____, and direct fusion.

endocytosis, phagocytosis, or viropexis

The process of penetration occurs when viruses are taken into the cell followed by engulfment in a vesicle called a(n) _____.

endosome

The total nucleic acid content of a virus can be referred to as the viral _____.

genome

Influenza, measles, and rabies are viruses that have a(n) _____ shaped capsid.

helical

The _____ range defines the limitations of the type of cell that a virus can invade.

host

Poliovirus and adenovirus have a capsid arranged in a symmetrical polygon structure called a(n) _____

icosahedron or icosahedral

Bacterial host cells undergo _____ due to the splitting open and release of bacteriophages.

lysis

A(n) _____ virus does not have an envelope surrounding its capsid.

naked

Viruses with single-stranded RNA genomes that have to be converted to the the "other strand of RNA" before it can be translated into proteins are called _____ --strand RNA viruses.

negative

The herpes zoster virus goes into latency in _____ cells.

nerve

The growth of viruses in cell culture is detected by the observation of _____, clear areas representing lysis of infected cells.

plaques

Viruses with single-stranded RNA genomes that can be directly translated into proteins are called _____-strand RNA viruses.

positive

HIV is described as a(n) _____ because it synthesizes DNA from RNA using reverse transcription.

retrovirus

The influenza virus has an RNA genome that is referred to as _____, because individual genes exist in separate RNA molecules.

segmented

A(n) _____ phage is a bacteriophage that incorporates itself into the host genome as a lysogenic prophage.

temperate

Bacteria that are lysogenized with phage may produce _____ that are harmful to the host.

toxins or enzymes

Phages can serve as transporters of bacterial genes from one bacterium to another in a a process called _____.

transduction

The suffix _____- is given to viral families.

viridae

Cell (tissue) culture is considered an "in _____" method to propagate virus.

vitro

In terms of numbers, how many genes can be found in some viruses?

~9 to 100s

Rank the following from smallest genome to largest genome.

1. Virus 2. Bacterium 3. Eukaryotic cell

By one estimate, viruses outnumber bacteria by which factor?

10

The current classification of viruses lists how many orders?

10

Approximately what percent of the human genome is viral DNA?

8

Which structure immediately encloses viral nucleic acid?

Capsid

At minimum, viruses are composed of which of the following?

Capsid and nucleic acid

Which of the following is the monomeric unit for a viral capsid?

Capsomer

Prions affect the normal proteins in the cell membranes of eukaryotic cells in which of the following ways?

Causing abnormal folding

Which are the criteria used in classifying viruses into families?

Chemical composition Genetic makeup Structure

Where are most RNA viruses replicated and assembled within the host?

Cytoplasm

Most _____ viruses will assemble their virions within the host cell's nucleus.

DNA

The smallpox virus contains which of the following nucleic acid(s)?

DNA only

Which is the main test done to diagnose an HIV infection?

Detection of specific antibodies in a patient's blood

The term virus was first used to describe the infectious agent of which of the following?

Disease of tobacco plants

What functions do capsid proteins perform for naked viruses?

-Attachment -Protection

Which of the following are not found in viroids?

-Capsid -Envelope -Mitochondrion -Metabolic pathways

Which of the following relate to all viruses?

-Capsid -Nucleic acid -Acellular

A single virion could contain a genome of which of the following?

-DNA only -RNA only

Viruses are composed of which of the following?

-DNA or RNA -Protein capsid

Which bird eggs are the most common choices for viral propagation?

-Duck -Chicken -Turkey

Identify all the methods that a virus can use to gain entry into an animal cell.

-Engulfment/phagocytosis of the virus -Fusion of the viral envelope and the cell membrane

Which of the following describes bacteriophages?

-Flexible tail -Polyhedral capsid head -Complex

_____ and _____ are the names of two different types of capsids.

-Helical -Icosahedral

Identify all of the components of a nucleocapsid.

-Nucleic acid -Capsid

Which of the following characteristics are correct for viruses?

-Obligate intracellular parasites -Infects very specific cell types -Acellular

Which of the following activities are not characteristics of viruses?

-Replicate independently -React to environmental factors -Metabolize food -Maintain homeostasis

A persistent infection could last how long in a host?

-Several days -Several weeks -Several years

The cause of viral infections remained unknown for many years longer than other types of infections due to which of the following reasons?

-The techniques used to observe other pathogens were useless with viruses. -Viruses are not visualized by light microscopes.

Identify 3 purposes of viral cultivation.

-To prepare vaccines -To identify viruses in clinical specimens -To study effects on host cells

Which are used for placement of a virus into a particular family?

-Type of capsid -Presence of envelope -Nucleic acid strand number -Viral size

Which 3 of the following are usual choices for live animal inoculation with viruses?

-White mice -Hamsters -Rats

Two ways in which newly assembled viruses are released from host cells are through _____ or exocytosis by enveloped viruses, and through _____(rupture) by naked viruses.

-budding -lysis, cell lysis, or lyses

Tropisms are tissue specificities of animal viruses for certain body cells, e.g., the hepatitis B virus targets the _____ and the mumps virus targets _____ glands.

-liver -salivary or saliva

Identify all the types of nucleic acid genomes which have been discovered carried by various bacteriophages.

-ssRNA -dsDNA -ssDNA

List the correct order of viral life cycle phases, starting with the first at the top.

1. Adsorption 2. Penetration/Uncoating 3. Synthesis 4. Assembly 5. Release

A poiliovirus-infected cell can release how many virions?

About 100,000

What are viruses called when they are infectious?

Active

What term is used to describe when a virus initially "sticks" to the host cell?

Adsorption

Which viral stage occurs first?

Adsorption

Mimiviruses and pandorvisiruses were first discovered in which organism?

Amoebas

Most enveloped viruses are which of the following?

Animal viruses

Which of the following is not effective treatment for viral infections?

Antibiotics

Typically, what is the immunological response against viral capsid and viral envelope antigens?

Antibody production

Why do antiviral drugs often have side effects in host cells?

Antiviral drugs block viral replication by targeting host cell functions

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

Assembly

Identify the different environments in which some viruses can replicate.

Bacterial, human, and animal cells

What is the source of the diphtheria toxin?

Bacteriophage

What term is used to describe viruses which infect bacteria?

Bacteriophages

Viruses with negative-strand RNA molecules must first be converted to which of the following in the process of replication.

Be converted into a positive-strand of RNA

AAV can only replicate in cells infected with _____.

adenovirus

It is well known that _____ have no effect on treating viral infections.

antibiotics

During the _____ step in the viral multiplication cycle, the genetic material is packaged into capsids to make virions.

assembly or maturation

Any virus that specifically infects bacteria is called a(n) _____.

bacteriophage or phage

A general concept of all viruses is that they require a host _____ in order to replicate.

cell

The _____ agent is a naked strand of RNA that is only expressed in the presence of hepatitis B virus.

delta