Chapter 6: Virus and Prions

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At a minimum, a viral genome must include genes for

-regulating the actions of the host cell-packaging the mature virus particles-synthesizing the viral capsid

Identify any of the following pathways which could produce proteins used by viruses.

1. Host DNA --> mRNA --> proteins used by viruses2. Viral positive-ssRNA --> proteins used by viruses

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

E. coli has about 4,000 genes in its chromosome. A virus that infects E. coli would be expected to have about ______ genes in its chromosome.

10

The smallest animal virus, parvovirus, is approximately what size?

20 nanometers

Which is the correct term to describe viral adherence to a host cell receptor?

Adsorption

is the viral process of attaching to the host cell receptor for the virus.

Adsorption

Identify the different environments in which some viruses can replicate.

Animal cells Bacterial cells Human cells

Identify any of the following which can be used as primary cell lines.

Any of the answers listed here

Identify prion related diseases.

Bovine spongiform encephalopathy Creutzfeldt-Jakob disease

Which structure immediately encloses viral nucleic acid?

Capsid

Identify all the components of the nucleocapsid.

Capsid Nucleic acid

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

Capsomere

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

Cytoplasm

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

Endocytosis

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 term is used to describe the phospholipid bilayer found surrounding the capsid of some viruses?

Envelope

True or false: The viral envelope and capsid are the same thing.

False Reason: The viral envelope is composed of phospholipids while the capsid is composed of capsomer proteins.

What are the viral spikes typically composed of?

Glycoproteins

Viruses which have symmetrical polygonal capsids are called ______.

Icosahedral

What is the term which describes a geometric viral form having 20 faces and 12 corners?

Icosahedrons

Which term refers to the persistence of bacteriophages within host cells?

Lysogeny

Which of the following best describes viruses?

Obligate intracellular parasites

Capsomeres are composed of _______. (Hint: it is a macromolecule)

PROTEIN

Which of the following best describe the relationship between viruses and their host cell?

Parasitism

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

Prophage

At minimum, all viruses are composed of _______

Proteins Nucleic acids

Identify the commonalities between temperate phages and lytic phages.

Release Biosynthesis of viral components Penetration Assembly Adsorption

What are viruses called which are capable of converting their RNA genomes into DNA?

Retroviruses

In some viruses, including HIV, the enzyme __________ ________ transcribes RNA into DNA.

Reverse Transcriptase

The sum total of the viruses associated with your body is called the ______.

Some viruses are in a dormant state in the body. The human virome includes viruses that infect our commensal bacteria.

Identify any benefits of viruses to people.

Some viruses control insect pests Some viruses can be modified to deliver genetic cures via gene therapy Some viruses control food pathogens

Which two of the following are cytopathic effects in virally infected animal cells?

Syncytia Inclusions

Which of the following is a multinucleated mass of cells due to the cytopathic effect of viral infection?

Syncytium

Which process involves gene recombination via bacteriophage transfer?

Transduction

True or false: Embryonic tissue can serve as a primary cell line for viral culture.

True

Which two of the following mechanisms are found to result in cancer caused by a virus?

Viral proteins cause changes in growth regulation, leading to cancer. The virus carries genes that can cause the cancer.

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

Viral specificity for host receptors

Identify the smallest pathogenic agent.

Virion

Which of the following is composed of only RNA?

Viroid

Which of the following statements regarding the membrane on an enveloped virus is true?

Viruses insert their own proteins in the membrane.

Which four of the following are not found in viroids?

a.) Metabolic pathwaysc.) Mitochondriad.) Envelopee.) Capsid

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

assembly

Which are the three main criteria used in classifying viruses into families?

b.) Genetic makeupd.) Structuree.) Chemical composition

The structure directly surrounding the viral nucleic acid is the ___________ , a coat of proteins.

capsid

Which is closest in physical proximity to the nucleic acid of a virus?

capsid

A(n) _________ is a protein subunit that forms the viral capsid.

capsomer

This helical capsid is comprised of protein subunits called _________

capsomer

The structure represented here as the protein subunit of a helical capsid is termed a ______.

capsomere

Most bacteriophages contain which type of nucleic acid?

dsDNA

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

dsDNA ssRNA ssDNA

Viral nucleic acids are ______.

either single-stranded or double stranded

The 2 principle processes by which viruses penetrate host cells are ___________ (engulfment) and direct fusion.

endocytosis

A(n) __________ virus has a membranous layer external to the nucleocapsid.

envelope

In this image of an enveloped virus, the red arrow is pointing to the ______.

envelope

Which types of viruses are released by budding?

enveloped virus

Budding is a type of ______ process where enveloped viruses are released from the host cell membrane.

exocytic

True or false: Bacteriophages infect eukaryotic and prokaryotic microorganisms.

false

______ viruses in the human body are pathogenic.

few

Which of the following term describes the total nucleic content of a virus?

genome

Viruses which have a series of rod-shaped capsomer proteins linked together forming a series of interconnected hollow discs are termed ______.

helical

Two shapes of viral capsids are ________, which resembles a bracelet; or __________, which is a type of polyhedron.

helical icosahedral

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

host

Viral transformation implies ______.

host DNA is changed

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

host range

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

induction

Typically, naked helical viruses are ______ flexible than enveloped helical viruses.

less

Hepatitis viruses have a tropism for cells of the ______.

liver

The process by which bacteriophages infect bacteria, conferring new traits enhancing human disease, is called ______.

lysogenic conversion

The cell component indicated by the arrow is a ______.

membrane receptor

Primary cells undergo which type of division to produce a monolayer for animal virus culture?

mitotic

The number of genes in a viral genome is _____ the number of genes in a bacterial genome.

much less than

Capsids of ______ helical viruses are rigid and tight, while capsids of ______ helical viruses are flexible and loose.

naked; enveloped

_______ refers to the capsid and nucleic acid of a nonenveloped virus.

nucleocapsid

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

nucleus

Bacteriophages can infect which of the following?

prok. only

At minimum, viruses are composed of nucleic acid covered by a coating comprised of ______

protein

The chemical composition of the cell membrane structure indicated by the arrow is ______.

protein

Which macromolecule composes capsomeres?

protein

An enzyme capable of taking an RNA genome and generating a DNA copy is called ______.

reverse transcriptase

A virus that only infects cells of a specific tissue in the body is described as having a ______.

tropism

The process of ___________ occurs when viruses lose their envelope during penetration into a host cell or when the envelope/capsid is are dissolved within a vacuole.

uncoating

Which term describes the process of a virus losing its capsid and exposing viral nucleic acids to the immediate environment?

uncoating

A fully formed virus that is able to establish an infection in a host cell is often called a ______.

virion

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

viroid

Cytomegaloviruses, Epstein Barr viruses, bacteriophages, and the remainder of the approximately 1015 viruses associated with a typical adult can collectively be referred to as that individual's ______

virome

A(n) is a microscopic, acellular agent composed of nucleic acid surrounded by a protein coat.

virus

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

vitro

When an enveloped virus buds off the cell membrane, the membrane differs ______ from the host cell's membrane.

significantly

Which of the following structures of enveloped viruses must be specific for adsorption?

spike proteins

Viral glycoproteins that protrude from the viral envelope and attach to host cell receptors are termed _______.

spikes

What term is used to describe the viral proteins which protrude from the envelope and aid in attachment to host receptors?

spikes

__________phage is a bacteriophage that incorporates itself into the host genome as a lysogenic prophage. Correct Answer Blank 1: temperate

temperate

The penetration step differs between animal viruses and bacteriophage in that ______.

the entire virus enters an animal cell, but only phage DNA enters a bacterial cell

Which of the following steps of the animal virus life cycle is not found in the bacteriophage life cycle?

the phage DNA is injected directly into the cell cytoplasm

Cell culture and_______ culture have the same meaning.

tissue


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