chapter thirteen: viruses, viroids, and prions

bacteriophage

A virus that infects bacteria; often shortened to phage.

viroid

An infectious agent of plants that consists only of RNA.

productive infection

Viral infection in which more viral particles are produced.

latent infection

Viral infection in which the viral genome is present but not active, so new viral particles are not being produced.

plaque assay

a method used to determine the number of infectious virions

the phospholipid bilayer found surrounding the capsid of some viruses is the ______. a) envelope b) phagosome c) cell membrane d) matrix e) vacuole

envelope

True or False: prion replication depends on the presence of a protease

false

______ is a change in the phenotype of a lysogen as a consequence of the specific prophage it carries. a) lysogenic conversion b) lysogenic cycle c) latency conversion

lysogenic conversion

HIV is described as a ______ because it uses reverse transcriptase to make a dna copy from its rna genome

retrovirus

cytopathic effect

The visible effect viruses have on cells

lytic infection

Viral infection of a host cell with a subsequent production of more viral particles and lysis of the cell.

temperate phages

bacteriophages that can choose to direct a lytic infection or lysogenic infection

True or False: there is no need to classify viruses because they are not living organisms

false

Which of the following contains only one type of macromolecule? i. RNA viruses ii. DNA viruses iii. Prions iv. Viroids v. RNA and DNA viruses a) (i), (iii), and (v) b) (ii) and (iii) c) (i) and (iv) d) (iii) and (iv) e) (i), (ii), (iii), (iv), and (v)

(iii) and (iv)

prion

An infectious protein that causes a neurodegenerative disease.

which type of viruses are released by budding? a) rna viruses b) non-enveloped viruses c) enveloped viruses d) dna viruses

enveloped viruses

True or False: viroids contain a capsid but lack an envelope

false

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

filamentous

which are the two main criteria used in classifying viruses? a) pathogenic potential b) genome structure c) geographic distribution d) capsid diameter e) host range

genome structure host range

the physical rupture of a cell is termed ______.

lysis

infection of bacteria by ______ phages always ends with the lysis of the host cell

lytic

in enveloped viruses, sandwiched between the nucleocapsid and the envelope is the a) endocapsid b) exocapsid c) exoskeleton d) matrix protein e) nucleocapsid

matrix protein

the molecules that viral spikes attach to on the host cell in order to gain entry are typically a) transport proteins b) lipoproteins c) lipopolysaccharides d) glycoproteins

glycoproteins

True or False: enveloped viruses enter the host cell by endocytosis only, while non-enveloped viruses can enter the host cell by fusion or endocytosis

false

the most important transmitters of plant viruses are probably a) birds b) animals c) soil d) contaminated seeds e) contaminated pollen f) insects

insects

most animal dna viruses will replicate within the host cell's ______

nucleus

lysogen

A bacterium that carries phage DNA (a prophage) integrated into its genome.

lysogenic conversion

A change in the properties of a bacterium, conferred by a prophage.

virion

A complete virus in its inert non-replicating form; also referred to as a viral particle.

Which of the following statements about human papilloma virus (HPV) are TRUE? (choose all that apply) a) HPV is more resistant to disinfectants than is herpes simplex virus. b) HPV may be carcinogenic. c) HPV is easily destroyed by disinfectants compared with herpes simplex virus. d) A person infected with HPV strain 16 will definitely develop cancer. e) A vaccine that protects against some dangerous strains of HPV is available.

HPV is more resistant to disinfectants than is herpes simplex virus HPV may be carcinogenic a vaccine that protects against some dangerous strains of HPV is available

which type of infection can be characterized by the sudden onset of symptoms of a relatively short duration? a) acute b) secondary c) primary d) persistent

acute

which are the two major categories of viral infections? a) asymptomatic b) chronic c) acute d) latent e) persistant

acute persistant

Influenza viruses bud from the host cell. Based on this information, the viruses most likely a) have an rna genome b) are enveloped c) form a provirus d) have a latent state e) are non-enveloped f) have a dna genome

are enveloped

Select the ways that plant viruses can infect plants. (choose all that apply) a) By direct contact with specific receptors on plant cell cytoplasmic membranes. b) By contact with intact and undisturbed plant cell wall structures. c) By contaminated insects feeding on plant cells and disrupting the cell wall. d) By soil that was previously used to grow infected plants. e) Through grafting infected plant tissue onto healthy tissue.

by contaminated insects feeding on plant cells and disrupting the cell wall by soil that was previously used to grow infected plants through grafting infected plant tissue onto healthy tissue

Select the possible hosts of prions. (choose all that apply) a) Plants b) Bacteria c) Humans d) Cattle e) Sheep f) Goats g) Deer h) Elk

humans cattle sheep goats deer elk

which of the following are the three general shapes of most viruses? (choose all that apply) a) icosahedral b) helical c) spherical d) complex e) diamond

icosahedral helical complex

protection of lysogens from infection by the same phage is called a) adaptive immunity b) lysogenic conversion c) reverse transcription d) immunity to superinfection

immunity to superinfection

Which of the following about viruses/viral infections is FALSE? a) The virus that causes chickenpox can establish a latent infection. b) Viruses are generally not considered to be "alive." c) Animal viruses often enter a cell via receptor-mediated endocytosis. d) Phages often enter a cell via receptor-mediated endocytosis. e) The virus that causes genital herpes can establish a latent infection.

phages often enter a cell via receptor-mediated endocytosis

Which of the following statements about plant virus transmission are TRUE? (choose all that apply) a) Plant viruses enter their host through wounds. b) Grafted plants may be at risk of virus infection. c) An animal infected with a virus can transmit that virus to a plant. d) An insect may transmit viruses between plants. e) Parasitic fungi may transmit plant viruses.

plant viruses enter their host through wounds grafted plants may be at risk of virus infection an insect may transmit viruses between plants parasitic fungi may transmit plant viruses

spikes

structures found outside of virions that binds it to the host cells

Bacteriophage MS2 is an icosahedral, (+) sense, single-stranded RNA phage. It infects E. coli and other members of the Enterobacteriaceae. It only infects strains of these bacteria that have produced a sex pilus. Based on the information given, which of the following are true about MS2? (choose all that apply) a) The bacterial receptor for MS2 is on the F (sex) pilus. b) MS2 is a virulent phage. c) MS2 is a temperate phage. d) The phage carries a replicase. e) MS2 carries a DNA polymerase. f) MS2 can only infect F+ bacteria.

the bacterial receptor for MS2 is on the F (sex) pilus MS2 is a virulent phage the phage carries a replicase MS2 can only infect F+ bacteria

the concentration of infectious phage particles in a sample is called the

titer

Please choose the statement that best describes the role of viral surface proteins or spikes. a) Viral spikes provide means for viruses to exchange nucleic acid. b) Viral spikes inject viral nucleic acid into host cell. c) Viral spikes provide means of attachment to host cell surface. d) Viral spikes allow viruses to bind to each other. e) Viral spikes enable replication of the viral nucleic acid.

viral spikes provide means of attachment to host cell surface

late proteins of the T4 lytic cycle include ______. (choose all that apply) a) viral envelope b) T4 tail fibers c) T4 chromosome d) T4 capsomere components e) nuclease to digest the host DNA

T4 tail fibers T4 capsomere components

the binding of a bacteriophage surface protein to a host cell receptor is called a) release b) entry c) synthesis d) attachment e) assembly f) fixation

attachment

lytic phages

bacteriophages that routinely lyse their host

the number of phage particles released from a host cell is called the ______ size.

burst

Streptococcus pneumoniae is a bacterial pathogen that can cause pneumonia. Laboratory studies of various subtypes of this organism by The Rockefeller University scientists revealed that some of them produced colonies of different opacity (cloudiness). They found that compared with bacteria from opaque colonies, bacteria from more transparent colonies were found to grow more quickly and to adhere more efficiently to bronchial cells in culture. They also found that the bacteria from transparent colonies contained a phage strain called MM1-1998. Based on this information, which of the following statements are TRUE? (choose all that apply) a) S. pneumoniae forming transparent colonies are lysogens. b) S. pneumoniae bacteria containing MM1-1998 have a competitive advantage. c) MM1-1998 affected genotype but not phenotype of the S. pneumoniae. d) Lysogenized S. pneumoniae is immune to infection by other strains of MM1. e) Providing that the culture conditions of the S. pneumoniae are unchanged, subsequent generations of this bacterium will also exhibit change in transparency and growth ability.

s. pneumoniae forming transparent colonies are lysogens s. pneumoniae bacteria containing MM1-1998 have a competitive advantage providing that the culture conditions of the s. pneumoniae are unchanged, subsequent generations of this bacterium will also exhibit change in transparency and growth ability

True or False: bacteriophages are important medically because they can be used to prevent the growth of food-contaminating pathogens

true

True or False: tumor tissue can serve as a cell line for viral culture

true

after a virus enters a cell, the nucleic acid separates from the protein coat, a process called

uncoating

Select the TRUE statements regarding reverse-transcribing viruses. (choose all that apply) a) They have a unique enzyme called reverse transcriptase. b) Their replication strategy goes against the central dogma of genetics. c) They have both RNA and DNA. d) They exhibit high mutation rates in their genomes. e) They infect primarily bacteria.

they have a unique enzyme called reverse transcriptase their replication strategy goes against the central dogma of genetics they exhibit high mutation rates in their genomes

which of the following are classified as persistent infections? (choose all that apply) a) chronic infections b) contagious infections c) endemic infections d) latent infections e) acute infections

chronic infections latent infections

You discover a new medication that prevents the activity of RNA-dependent RNA polymerase. Which of the following will be affected by this medication? (choose all that apply) a) Ebola virus b) Herpes zoster virus c) Human immunodeficiency virus d) T4 phages e) Polioviruses

ebola virus polioviruses

the phage dna that is latently incorporated into the bacterial host genome is called a a) persistent infection b) temperate c) provirus d) prophage e) lysogenic f) bacteriophage

prophage