An organism or virus that can live or multiply only inside a living host cell
i.e. chlamydias and rickettsias
What are the components of a virus?
Nucleic acid
Capsid
Envelope
A nucleic acid core and a surrounding protein coat is called a _?
capsid
Some viruses have a lipid bilayer membrane called an _?
envelope
A complete virus particle including its envelope is called a _?
virion
what is a genome?
genetic information in an organism
each capsid is composed of protein subunits called _?
capsomeres
What do enveloped viruses have outside thier capsid?
a typical bilayer membrane
what is a nucleocapsid?
the nucleic acid and capsid of a virus
A virus with only a nucleocapsid and without an envelope
naked
projections extending from the envelope?
spikes
What are spikes made of?
glycoproteins that serve to attach virions to specific receptor sites
What is the most common polyhedral capsid shape?
icosahedral
complex viruses have a more elaborate _?
coat or capsid
viruses that infect bacteria
bacteriaphages
what is host range
referst to the spectrum of hosts that a virus can infect.
refers to the specific kinds of cells a virus can infect
viral specificity
what is the ICTV
International Committee on Taxonomy of Viruses
what is viridae
family name
what are the positive sense, single stranded RNA viruses that cause human diseases
Polio, Common cold, Hep A, Rubella/german measles, equine encephalitis, yellow fever, adult leukemia, tumors, AIDS
What are the negative sense, single stranded RNA viruses that cause human diseases
Measles, rabies, Influenza A and B, Marburg, Ebola, Respiratory distress, hemorrhagic fevers
What are the double stranded RNA viruses that cause human disease
respiratory and gastrointestinal infections
What are the double stranded DNA viruses that cause human disease
respiratory infections, oral and genital herpes, chickenpox, shingles, smallpox, cowpox, warts, cervical and penile cancers, hepatitis B
What are the single stranded DNA viruses that cause human disease
fifths disease in children
Does DNA or RNA mutate?
RNA mutate because there is no spell checker
DNA has a spell checker to cut out mutants
What are emerging viruses
viruses that were perviously endemic (low levels of infection in localized area) or had crossed species barriers
What are the steps in viral replication
1) adsorption - attachment of virus to host cell
2) Penetration - entry of virion
3) synthesis - of new nucleic acid molecules & capsid protien using the cell machinery
4) maturation - assembly of newly synthesized viral components
5) release - departure of new virions from host cells
The use of highly specific viruses that attack only the targeted bacteria and leave potentially beneficial bacteria that normally inhabit the human digestive tract and other locations alive.
Phage therapy
bacteriophage therapy
What is growth measured by?
by # not size
the period during which viruses have absorbed to and penetrated host cells but cannot yet be detected in cells
eclipse period
period of a bacteriophage growth curve that spans the time from penetration through biosynthesis
latent period
plaque assay
A viral assay used to determine viral yield by culturing viruses on a bacterial lawn and counting plaques
count the spots that growth was killed
A plaque forming unit PFU
a plaque counted on a bacterial lawn that gives only an approximate number of phages present, because a given plaque may have been due to more than one phage
A bacteriophage that does not cause a virulent infection; rather its DNA is incorporated into host cells chromosome, as a prophage, and replicated with the chromosome
temperate phage
a stable, long term relationship between the phage and its host in which the phage nucleic acid becomes incorporated into the host nucleic aicd
lysogeny
The viral DNA within the bacterial chromosome
prophage
the combination of temperate phage and bacterium
lysogen
The ability of a prophage to prevent additional infections of the same cell by the same type of phage; also the conversion of a non-toxic-producing bacterium into a tonix-producing one by a temperate phage
lysogenic conversion
Which cycle is the virulent cycle
lytic cycle
what cycle may stay hidden forever or breaks out into virulent
lysogenic cycle
Culture made from a single tissue, assuring a reasonably homogeneous set of cultures in which to test the effects of a virus or to culture an organism
tissue culture
A culture in the form of a monolayer from dispersed cells and continous cultures of cell suspension
Cell culture
A suspension of cells that attach to plastic or glass as a sheet one layer thick
monolayer
The process by which cells from an existing culture are transferred to new containers with fresh nutrient media
subculturing
come directly from the animal and are not subcultured
primary cell cultures
If primary cell cultures are repeatedly subcultured, one cell type will become dominant, and the culture is called a _.
cell strain
The visible effect viruses have on cells
cytopathic effect, CPE
The introduction of defects during embryonic development
teratogenesis
a drug or other agent that induces defects into the fetus
teratogen
series of blood tests, sometimes used to identify possible teratogenic diseases in pregnant women and newborn infants.
TORCH series
AKA virusoids, small single-stranded RNA molecules that lack genes required for their replication. they require a helper virus (or satellite) to replicate
satellite nucleic acids
Small single stranded RNA molecules, usually 500 to 2,000 nucleotides in length, which lack genes required for their replication. They require a helper (satellite) to replicate
satellite virus
an infectious RNA particle smaller than a virus
(short strips of RNA that cause color changes in plants)
viroids
Viroids differ from viruses in 6 differet ways
1) each viriod consist of a singular circular RNA molecule of low molecular weight, 246 to 399 nucleotides in length
2) Viroids exist inside cells, usually inside of nucleoli, as part of RNA without capsids or envelopes
3) Unlike viruses such as the parvoviruses, viroids do not require a helper virus
4) viroid RNA does not produce proteins
5) unlike virus RNA, which may be copied in the host cell's cytoplasm or nucleus, viroid RNA is always copied in the host cell nucleus
6) Viroid particles are not apparent in infected tissue without the use of special techniques to idenitfy nucleotides sequence in the RNA
an exceedingly small infectious particle consisting of protein without any nucleic acid
1) prions are resistant to inactivation by heating to 90C, which will inactivate viruses
2) prion infection is not sensitive to radiation treatment that damages virus genomes
3) Prions are not destroyed by enzymes that digest DNA or RNA
4) prions are sensitive to protein denaturing agents such as phenol and urea
5) prions have direct pairing of amino acids
what are virus nucleic acids and hosts
ssDNA
dsDNA
ssRNA
dsRNA
effects - bacteria, animals, plants
what are the nucleic acid and host of viroids
ssRNA
effects - plants
what are the nucliec acids and hosts of prions
no nucleic acid
effects mammals
uncontrolled, invasive growth of abnormal cells
cancer
localized accumilation of cells known as a tumor
neoplasm
non-cancerous growth
benign
cells that invade and interfere with the functioning of surrounding normal tissue
malignant
malignant tumors and their cells can spread to other body tissues
metastasize
the proteins produced by tumor viruses that cause incontrolled host cell division come from segments of DNA called_
oncogenes
surrounding protein coat
capsid
complete virus particle, including envelope if it has one
virion
projection made of gylcoproteins that serves to attach virions to specific receptor sites
spikes
surrounding lipid bialyer membrane
envelope
virus with a nucleocapsid but no envelope
naked virus
virions genome together with capsid
nucleocapsid
a chemical component that is found in all viruses is:
A) protein
a common polyhedral capsid shape of viruses is:
A) icosahedron
true or false:
viruses are capable of infecting all life forms; some can even infect members of different kingdoms but most are limited to only one host and olny specific cells and/or tissue of that host
true
enteroviruses differ from rhinoviruses mainly in thier
B) ability to survive acidic conditions
Which of the following proterites do viruses have in common with the bacterial section containing Reckettsiae and Chlamydiae.
C) they are both obligate intracellular parasites
viruses that remain latent (usually in neurons) for many years are most likely:
A) herpesviruses
what type of viruses contain the enzymes lysosome to aid in their infection:
E) bacteriophages
viruses that infect bacteria are called:
A) bacertiophages
bacteriophages are readily counted by the process of:
B) plaque assay
the type of cell culture that can be reproduced for an extended number of generations and is used to support viral replication is:
B) continuous cell line
Which of the following is not a DNA virus:
C) orthomyxovirus
what are the general replication steps in order
1) adsorption - attachment of virus to host cell
2) penetration - entry of virion genome into host cell
3) synthesis - host metabolic machinery is used to produce new nucleic acid molecules, capsid proteins, and other viral components
4) maturation - assembly of newly synthesized viral components into complete virions.
5) release - departure of new virions from host cell, generally with lysis of host cell
bacteriophages that can enter into stable, long-term relationships with their hosts are called:
D) temperate phages
the positive (+) strand RNA of certain viruses does not act as a message but becomes converted into DNA and integrated into the host cellular DNA. These viruses are:
C) retroviruses
immortalized cells that produce for an extended number of generations
continuous cell line
cells that come directly from the animal, have very few cell divisions, but support the growth of a wide variety of viruses
primary cell culture
trypsinized and washed cells that attach to plastic surfaces where they mulitply and spread to form sheets one cell thick
monolayer
cells from an existing cell culture are transferred to new containers with fresh nutrient media
subculturing
visible effects viruses produce in infected host cells
cytopathic effect CPE
immature, fetally derived cell types that rapidly divides numerous times and supports a wide range of viruses
diploid fibroblast strain
Creutzfeldt-Jakob disease (CDJ), kuru, scrapie, and mad cow disease are caused by:
D) prions
The human virus that has been associated with Burkett's lymphoma (a malignant tumor of the jaw) is:
C) epstein-barr virus
infectious, incorrectly folded protein
prion
small, single-stranded RNA virus lacking genes required for tis replication, and needing a helper virus
satellite
helper virus codes for its capsid
virusiod
code for their own capsid protein
satellite viruses
infectious RNA particles smaller than a virus
viroids
similar to a viroid and virusoids, a defective pathogen requiring the presence of hepatitis B virus for its replication
delta hepatitis virus
viruses that can induce defects during embryonic development (teratogenesis) in humans:
B) a, b, and d
eclipse period, latent period and viral yield
eclipse period - period during which viruses have absorbed to and penetrated host cells but cannot yet be detected in cells.
latent period - period of a bacteriophage growth curve that spans from the time of penetration through biosynthesis
viral yield - AKA burst size - the number of new virions released in the replication process
