chapter 7 viruses and prions
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56 Terms
vaccine, smallpox, virus, living, smaller, bacteria, rabies, vaccine, virus
the search for elusive viruses
edward jenner developed the first .. in the world against … in 1796
did not realize he was vaccinating against a …
pasteur believed that something .. that was .. than a … caused …
developed the first rabies … in 1884
coined the word … to name what caused rabies
tobacco, tobacco mosaic, foot, mouth, cattle, filterable, plants, animals, alive
the search for elusive viruses
ivanovski and beikerinck showed that … plants could be infected by … … virus
loeffler and frosch discovered … and … disease in …
this work led to the idea that viruses were …. agents
this work also showed that both … and … could be infected by viruses
viruses can infect anything ….
infectious particles, active, inactive, obligate intracellular, multiply, host, genetic, metabolic, host, make, release new
the position of viruses in the biological spectrum
… …
rather than organisms
…. or ….
rather than alive or dead
…. …. parasites
cannot … unless they invade a specific …. cell
must instruct the .. and … machinery of the … cell to … and …. …. viruses
ultramicroscopic, smaller, bacterium, electron
the general structure of viruses
…. size
… than the average ….
…. microscopes are required to detect them
protein, invade, control, host, external coating, core, nucleic acids
the general structure of viruses
lack … synthesizing machinery
need only those parts to … and … a … cell
…. …
…. containing … …
capsid, protein shell, nucleic acid, nucleic acid, genetic, dna or rna, capsid, nucleic acid, simplest
the general structure of viruses
viruses must have 2 things
1. ……
… … that surrounds the … …
2. … ….
… material that will be … …. …
nucleocapsid = … + … …
… viruses are nucleocapsid
project, nucleocapsid, envelope, dock, host, envelope, present, absent, fully, infection, host
the general structure of viruses
spikes
… from either the … or …
allow viruses to … with their … cells
may also have an …
enveloped: envelope is …
naked: envelope is …..
virion
…. formed virus able to establish … in a ….
identical protein, self, capsid, capsids, helical, rod, continuous helix, nucleic acid, icosahedral, round, 3, 20, 12 evenly, corners
the general structure of viruses
capsomeres:
.. … subunits that spontaneously .. assemble to form the … (building blocks of …)
2 typical shapes
… capsid: … shaped capsomeres that form a .. .. around the .. ..
… capsid: … capsomeres that form … dimensional, … sided figure with … …. spaced ….
poxvirus, membranes, surface fibrils, bacteriophage, bacteria, multiple, proteins, shapes, symmetrical
the general structure of viruses
complex capsids:
… have a unique and complex structure unlike others
consist of … and … …
found in …, the viruses that infect …
have … types of …
take … that are not …..
membrane, host, cell, nuclear, virus, host, regular, viral
the general structure of viruses
envelope is composed of the …. system of the …..
may come from either … membrane or … membrane as the … leaves the … cell
…. membrane proteins are replaced with … proteins
full complement, dna, rna, cell, not both, viral, small, cell, necessary, invade host, redirect, activity
the general structure of viruses
genome: the … … of … and … carried by a …
viruses contain either dna or rna but … …
the number of … genes is … compared to that of a …
possess only the genes …. to … … cells and … their ….
single, rna, translation, proteins
the general structure of viruses
positive sense rna
… stranded .. genomes ready for immediate …. into ….
rna, converted, form, proteins
the general structure of viruses
negative sense rna
… genomes that need to be … into the proper … to be made into ….
single, rna reverse transcriptase
the general structure of viruses
.. stranded …. …. …. are retroviruses
polymerases, dna, rna, replicases, rna, reverse transcriptase, dna, rna, arenaviruses, host ribosomes, retroviruses, trna
the general structure of viruses
enzymes for specific operations within the host cell
…..: synthesize .. and …
….: copy …
… …: synthesizes … from ….
substances from the host cell
….. pack along the … …
… borrow the host’s … molecules
animal, plant, bacterial viruses, dna, rna, helical, icosahedral, structure, chemical, similarities
how viruses are classified and named
informal classical system
…., …, or … …
…. or …. viruses
… or …
criteria of a formal classification system
….
…. composition
…. in genetic makeup
adsorption, host, penetration, host cell membrane, uncoating, virus penetrates, synthesis, nucleic acid, assembly, automatically, parts, manufactured, available, release, host, kill
modes of viral multiplication
general phases in the life cycle of animal viruses
…. - must occur with a susceptible … cell
…. - occurs at the … … …
…. - depends on how the … … the cell
…. - depends on the viral .. .. (dna or rna)
… - happens .. as viral … are … and …
… from the … cell - may or may not …. the host
host, adsorbs, receptor, membrane, attach, virus, soak
modes of viral multiplication
invasion begins when the virus encounters a susceptible … and …. specifically to … sites on the cell …
adsorb - to … (like a …)
absorb - to … in (like a paper towel)
exact, molecule, liver, humans, intestinal, nerve, primates, various, all mammals
modes of viral multiplication
host range
a virus can invade its host cell only through making an … fit with a specific host …
restricted host range: hepatitis B only infects … cells of ….
moderately restrictive host range: poliovirus infects … and … cells of ….
broad host range: rabies virus infects … cells of … ….
membrane, entire, engulfed, cell, vacuole, vesicle, naked, enveloped, envelope, membrane, nucleocapsid, enveloped, enzymes, vacuole, envelope, capsid, cytoplasm
modes of viral multiplication
penetration: occurs at the cell ….
1. endocytosis - … virus is … by the … and enclosed in a … or … (… or …)
2. fusion - … fuses with … and only … enters the cell (… only)
uncoating - .. in the .. dissolve the .. and …, releasing the virus into the ….
nucleic acid, control, synthetic, metabolic, dna, rna, cytoplasm, nucleus
modes of viral multiplication
synthesis - viral … … takes … over the host’s … and … machinery
mechanism varies depending on whether the virus is a … or … virus
rna virus replicate in the …
dna virus replicate in the …
parts, synthesis, pool, mature, made, enveloped, bud, host envelope
modes of viral multiplication
assembly - the … of the virus made during .. accumulate into a … and … virus particles can be …
… viruses … off with the .. …
kill, enveloped, budding, exocytosis, membrane, pouch, pinching, releases, envelope, shed, without, cell
modes of viral multiplication
release - may or may not .. the host
… viruses are liberated by … or ….
nucleocapsid binds to the …
a small .. is formed
.. off of the pouch … the virus with its …
viruses are .. gradually … destruction of the …
damage, infection, microscopic, disoriented, major, shape, size, intracellular
modes of viral multiplication
cytopathic effects (CPEs) - … done to the host cell during the process of ….
virus induced damage to the cell that alters its … appearance
cells can become …, undergo … changes in … or …, or develop … damage
compacted masses, damaged, organelles, nucleus, cytoplasm
modes of viral multiplication
inclusion bodies - … .. of viruses or … cell .. in the .. or …
fusion, multiple host, single large, nuclei
modes of viral multiplication
syncytia (syncytium) - … of .. .. cells into .. .. cells containing multiple …
weeks, rest, harbors, carrier, harbors, lysed, incorporated, dna, host, hiv, integrated, activation, period, inactivity, chicken pox
modes of viral multiplication
persistent infection - an infection that can last .. to the .. of the host’s life because the host cell … the virus
a .. relationship that develops in some cells
cell …. the virus and is not immediately ..
provirus - viral dna … into the .. of the …. (…)
estimates say approximately. 8% of human dna is …. virus
chronic latent state - periodic … after a .. of viral … (herpes, … …)
cancers, viruses, cancer, proteins, loss, growth
modes of viral multiplication
oncogenic viruses
experts estimate that up to 13% of human … are caused by …
transformation
virus carries genes that directly cause …
virus produces … that induce a … of … regulation in the cell
bacteria, replication, different, animal, bacterial, pathogenic
modes of viral multiplication
bacteriophage - a virus that infects … and has … cycles … from … viruses
parasitize every known … species
often make the bacteria they infect more … for humans
e. coli, 2, 4, studied, similar, animal
modes of viral multiplication
T-even bacteriophage infect … …
T - …. and T- ….
most widely … bacteriophage
go through …. stages as … viruses
life, bacteriophage, destruction, bacterial, bacteriophage, incorporated, dna
modes of viral multiplication
lytic phase or lytic cycle - … cycle of … that ends in … of the … cell
lysogenic cycle - … becomes … into the host cell …
adsorption, penetration, duplication, phage, replication, virus, assembly, new virions, maturation, lysis, weakened, release
modes of viral multiplication
lytic cycle
……
….
… of .. components, … of … genetic material
….. of … ..
….
… of .. cell
…. of viruses
adsorption, penetration, latent, prophage, inserted, sites, chromosome, duplicated, regular, adaptive
modes of viral multiplication
lysogenic cycle
….
….
viral dna becomes … as ….
the viral dna molecule is … at specific … on the bacterial …
the viral dna is .. along with the … genome and can provide .. genes for the host bacterium
silent viral infection, adsorption, penentration, not, replication, release, inactive, phage dna, inserted, chromosome, activation, prophage, lysogenic, directly, replication, lytic
modes of viral multiplication
lysogeny is considered to be a .. .. ….
temperate phages
have the ability to undergo … and … but do .. immediately undergo … or …
prophage: an … state in which .. .. is .. into the host ….
induction: … of a .. in a … cell to progress … into viral … and the .. cycle
humans, phage, toxins, enzymes, pathology, new, temperate, diphtheria, cholera, botulism
modes of viral multiplication
lysogeny can be dangerous to … - occasionally … genes in the bacterial chromosome cause the production of … or … that cause … in the human
lysogenic conversion
the acquisition of a … trait from a … phage
responsible for the … toxin, … toxin, and … toxin
attachment, tail fibers, wall, capsid, envelope, surface receptors
comparison of bacteriophage and animal virus infection
adsorption
bacteriophage
precise … of special .. .. to cell ….
animal
attachment of … or … to cell … ….
injection, nucleic acid, wall, uncoating, nucleic acid, engulfed, uncoated, surface, membrane, released
comparison of bacteriophage and animal virus infection
penetration
bacteriophage
… of .. .. through cell ….; no .. of .. …
animal
whole virus is .. and … or virus … fuses with cell …; nucleic acid is …
cytoplasm, cessation, synthesis, replicated, function, synthesized, cytoplasm, nucleus
comparison of bacteriophage and animal virus infection
synthesis and assembly
bacteriophage
occurs in ….
.. of host ….
viral dna or dna is … and begins to …
viral components …..
animal
occurs in … and …
everything else is the same
lysogeny, latency, chronic, cancer
comparison of bacteriophage and animal virus infection
viral persistence
bacteriophage
…..
animal
…
… infection
…..
lyses, enzymes weaken, some, lyse, enveloped, bud, membrane
comparison of bacteriophage and animal virus infection
release from host cell
bacteriophage
cell … when viral … … it
animal
.. cells …
… viruses .. off host cell ….
immediate, delayed
comparison of bacteriophage and animal virus infection
cell destruction
bacteriophage and animal
… or …
cultivation, animals, embryonic bird tissues, cultivation, cell, tissue, isolate, identify, clinical, vaccines, structure, multiplication, genetics, effects, host
techniques in cultivating and identifying animal viruses
in vivo methods: viral … in lab … or .. … …
in vitro methods: viral .. in .. or .. culture
primary purposes of viral cultivation: … and … viruses in … specimens
prepare viruses for …
do detailed research on viral …
…. cycles
….
and … on .. cells
mice, rats, hamsters, guinea pigs, rabbits
techniques in cultivating and identifying animal viruses
specially bred strains of animals used for animal cultivation of viruses
white …
…
…
… …
….
brain, blood, muscle, body, skin, footpads
techniques in cultivating and identifying animal viruses
injection sites for viral exposure
…..
…
…
… cavity
…
…..
protective shell, intact, self, sterile, nourishment, embryonic tissues, multiplication
techniques in cultivating and identifying animal viruses
benefits of using bird embryos for cultivation
embryonic development occurs in a … …
… and … supporting unit with its own … environment and …
furnishes several .. .. that support viral ….
populations, animal, dishes, propagated, culture, developing, maintaining
techniques in cultivating and identifying animal viruses
cell culture or tissue culture: in vitro virus cultivation systems
a simple and effective way to grow …. of isolated … cells in culture ..
most viruses are … through cell …
much of a virologist’s work involves … and … cultures
primary, continuous, animal tissue, growth, mitotic, monolayer, surface, characteristics, original, chromosome numbers, rapidly, morphology, subculture, fresh nutrient
techniques in cultivating and identifying animal viruses
… and … cell cultures are commonly used
primary cultures
freshly isolated … … placed in a … medium
cells undergo … division, producing a … on the …
retain the … of the … tissue
continuous cultures
have altered … …
grow …
show changes in …
can be continuously … if they are given .. .. media
degeneration, lysis, infected, clear, well, patches, sheet, macroscopic, cytopathic, infected, radiate, infect, gradually, symmetrically, original
techniques in cultivating and identifying animal viruses
viral growth can be detected in culture by looking out for … and … of … cells
plaques
…, … defined .. in the cell …
… manifestations of … effects
develops when viruses released from an … cell … out to surrounding cells and .. them
infection spreads … and .. from the … point of infection
insidious, acute, hospitalization, colds, certain, dengue fever
viruses and human health
impossible to measure the number of viral infections worldwide accurately
viruses are often …
most common cause of … infections do not result in ….
…., chicken pox, influenza, herpes, warts
viral infections that only occur in certain regions
… …, rift valley fever, yellow fever
rabies, ebola, polio, neonatal rubella
viruses and human health
some viral infections have high mortality rates
…. (close to 100%)
…. (average risk is 50% but can be between 20-90%)
other viral infections lead to long term disability
…
… ….
rapid, difficult, vaccines, few, ineffective, naturally, human, product, preventing, treating
viruses and human health
viruses mutate at a … rate
… to design therapies against viruses
scientists focus on developing …. against viruses since so …. antiviral drugs are available and antibiotics are …..
interferon (IFN)
… occurring .. cell …
used with some success in .. and … viral infections
chronic, persistent, humans, animals, brain tissue, affected, sponge
prions and other noncellular infectious agents
spongiform encephalopathies
implicated in …., … disease in … and …
… … removed from … animals resembles a ….
spongiform encephalopathies, protein fibrils, brain tissue, unknown, protein, no nucleic
prions and other noncellular infectious agents
prions
common feature of … …
distinct … .. deposited in … …
exact mode of infection is …
…. composition of prions has revolutionized ideas of what can constitute an infectious agent
questions about how prions replicate given that they have …. …. acid
central, humans, degeneration, death, unknown, sheep, cows
prions and other noncellular infectious agents
ctutzfeldt jakob disease (CJD)
afflicts the … nervous system of …
causes gradual … and …
transmissible by an … mechanism
several animals are victims of similar disease
scrapie: ……, mink elk
bovine spongiform encephalopathy: …..
dependent, replication, replicate, infected, adenovirus, disrupted
prions and other noncellular infectious agents
satellite viruses
… on other viruses for …
adeno-associated virus (AAV)
originally thought that it could only .. in cells … with the …
now found to infect cells infected with other viruses or that have had their dna … through other means
plants, one tenth, naked, rna, lack, capsid, coating, tomatoes, potatoes
prions and other noncellular infectious agents
viroids
virus like agent that parasitizes ….
about …. … the size of an average virus
composed only of … strands of … - … a … or other type of …
significant pathogens in economically important plants: …., …., cucumbers, citrus trees, and chrysanthemums
Note 
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