Term
This is a virus that infects a bacteria |
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Definition
bacteriophage (often shortened to Phage) |
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Term
Why are viruses difficult to study? |
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Definition
B/c they are obligate intracellular parasites. (They require another living organism as a host) and they are tiny. |
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Term
A nucleic acid surrounded by a protein coat. |
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Definition
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Term
The protein coat of viruses |
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Definition
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Term
The nucleic acid together with the protein coat is called a ________. |
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Definition
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Term
Viruses that do not have an envelope. |
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Definition
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Term
How are enveloped viruses different than naked viruses? |
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Definition
In general, enveloped viruses are more susceptible to disinfectants because they damage the envelope and the virus becomes non-infectious. |
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Term
Most phages are what type of virus? |
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Definition
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Term
What are three ways that viruses can be transmitted from one organism to another? |
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Definition
sexual contact,enteric(oral/fecal) respitory or salivary, vector(arthropods)(e.g. tics)(zootonic) |
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Term
Viruses so named because they are spread by mosquitos, ticks, and sandflies |
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Definition
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Term
These phages exit the host cell by causing it to lyse at the end of an infection cycle. |
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Definition
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Term
Viral infections that result in new virus particles |
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Definition
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Term
What are the five phases of the infection cycle of virulent phages? |
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Definition
1. attachment 2. genome entry 3. synthesis of proteins and genome 4. Assembly(maturation) 5. Release |
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Term
These phages have the option of either directing lytic or lysogenic infections |
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Definition
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Term
In this type of infection, viral DNA is incorporated into the host cells' genome |
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Definition
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Term
A change in the phenotype of a lysogen as a consequence of the specific prophage it carries. |
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Definition
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Term
Why is lysogenic conversion inportant from a medical standpoint? |
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Definition
Strains of typical bacteria begin producing toxins that would not be produced by the cell otherwise. This increases the pathogenicity of certain strains of bacteria. |
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Term
This type of transduction results from a packaging error during phage assembly. Short DNA fragments can be mistakenly packaged into the phage head during assembly. |
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Definition
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Term
A phage head that contains only bacterial genes in place of phage genes cannot direct a phage replication. these are called what? |
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Definition
generalized transducing particles |
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Term
This type of transduction results from an excision mistake made by a temperate phage during its transition from the lysogenic to the lytic cycle. |
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Definition
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Term
What are the 3 main shapes of viruses? |
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Definition
Icosohedral, helical, and complex |
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Term
What type of virus cause productive infections, but do not kill the host cell? |
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Definition
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Term
What would be the main cause of a temperate phage remaining in the lysogenic phase? |
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Definition
Low nutrition usually means the virus will stay in the lysogenic cycle |
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Term
What is the phage both prevents and maintains the lysogenic state? |
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Definition
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Term
How does the repressor protein both prevent and maintain the lysogenic state? |
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Definition
It doesn't allow another phage to enter the cell, but it keeps the one already there in the lysogenic state. |
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Term
If the DNA of a cell in the lysogenic state is damaged, what happens? |
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Definition
The SOS repair system will activate protease, the protease destroys the repressor, the prophage will be excised (enter the lytic cycle) |
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Term
What is one way to count phages? |
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Definition
Plaque assay (circular zones of clearing due to cell lysis caused by the phage) |
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Term
What is one way we could possibly target viruses with antiviral drugs? |
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Definition
Virus replication depends a lot on virally encoded enzymes...they are a good target for antiviral drugs. |
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Term
What is the 5 step infection process of animal virus replication? |
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Definition
1. attachment 2. penetration and uncoating 3. synthesis 4. assembly 5. release |
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Term
What is the main difference between generalized and specialized transduction? |
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Definition
In specialized transduction, only the bacterial genes adjacent to the integrated phage DNA can be transferred. In general transduction, any gene of the donor may be transferred. |
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Term
In what way do bacteria defend themselves against phages by deterring attachment of the phage? |
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Definition
THey cover the receptor on the cell surface so the virus cannot attach |
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Term
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Definition
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Term
These protect bacteria from phage infection by quickly degrading incoming foreign DNA by using restriction and modification enzymes. |
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Definition
Restriction-modification system |
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Term
What is one tool scientists use to remove genes from one DNA molecule and join them to another? |
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Definition
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Term
How does the bacteria protect its own DNA from degradation by restriction enzymes? |
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Definition
It methylates its own DNA, and only DNA that is unmethylated(phage DNA) will be destroyed. |
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Term
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Definition
Clusters of Regularly Interspersed Short Palindromic Repeats |
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Term
A chromosomal region in the bacterial cell that holds spacer DNA |
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Definition
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Term
What is the benefit of CRISPR? |
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Definition
It holds a historical record of phage infections, allowing bacteria and its progeny to block subsequent infections by the same phage. |
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Term
The concentration of infectious phage particles in the original phage solution |
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Definition
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Term
in absorption, the attachment of what triggers endocytosis? |
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Definition
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Term
What are the two main methods of viral entry? (absorption) |
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Definition
Endocytosis and membrane fusion |
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Term
What do viruses usually bind to on the outer cell wall? |
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Definition
specific receptors , glycoproteins on the plasma membrane (often more than one required) |
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Term
Why can most viruses only infect a certain species? |
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Definition
because they bind to specific receptors not usually found in every living animal |
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Term
In an _____ virus, the entire virion is taken into the cell. |
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Definition
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Term
IN this type of penetration and uncoating, the lipid envelope of the virion fuses with the plasma membrane of the host cell and releases the nucleocapsid directly into the cytoplasm. |
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Definition
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Term
In this type of penetration, the virion exploit normal cell receptor-mediated endocytosis to bring themselves into the cell. |
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Definition
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Term
Where do most DNA viruses multiply in animal cells? |
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Definition
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Term
IN all viruses, the nucleic acid separeates from its protein coating prior to the start of replication, this is the process of _______. |
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Definition
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Term
What two distinct, but interrelated events must occur for the synthesis of viral proteins and replication of the genome? |
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Definition
1.) expression of viral genes to produce structural and catalytic proteins 2.) synthesis of multiple copies of the viral genome. |
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Term
What type of viruses use the host cells machinery for DNA synthesis? |
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Definition
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Term
What is the main difference btwn dsDNA virses and ssDNA viruses in replication? |
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Definition
The ssDNA must first make a template and then begin making copies. |
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Term
What type are most RNA viruses? |
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Definition
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Term
Where do most ssRNA viruses replicate? |
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Definition
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Term
What does RNA replication require? |
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Definition
virally encoded RNA polymerase called replicase |
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Term
How is the replication of RNA viruses different from DNA viruses? |
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Definition
RNA viruses must synthesize RNA from an RNA template instead of a DNA template. |
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Term
Why do RNA viruses generally have higher rates of mutations, and why can this be beneficial for them? |
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Definition
The replicase (RNA virsu RNA polymerase) does not have proofreading ability=more mistakes. It can be beneficial because RNA viruses can adapt more quickly than DNA viruses. |
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Term
A type of antigenic variation that may cause a person whose immune system protected against one viral strain to not work against the next. |
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Definition
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Term
What type of enzyme do reverse-transcribing viruses for? |
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Definition
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Term
What does reverse transcriptase do? |
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Definition
synthesizes a DNA strand from an RNA strand. |
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Term
This kind of virus has a (+) RNA strand and carries reverse transcriptase with it. |
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Definition
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Term
In what way do most viruses release? |
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Definition
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Term
The process of a virus acquiring its envelope |
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Definition
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Term
Where does assembly take place in an animal virus? |
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Definition
In the nucleus or cytoplasm depending on the virus |
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Term
How does the virus obtain its viral envelope through budding? |
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Definition
The virus protein spikes insert themselves into specific regions of the host cells membrane. Matrix proteins accumulate on the inside surface of those regions. Assembled nucleocapsids then extrude from the cell becoming covered by a layer of matrix protein and lipid envelope in the process. |
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Term
Does budding cause cell death? |
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Definition
not necessarily. The membranes can be repaired after the viral particles exit. |
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Term
How are naked viruses released? |
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Definition
Many viruses trigger apoptosis prior to the release of viral particles. |
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Term
How do enveloped viruses exit the cell? |
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Definition
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Term
Why are virally encoded enzymes medically important? |
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Definition
Because they are important in many viral processes and can be targeted to stop the virus from infecting. |
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Term
What type of infection is characterized by a sudden onset of symptoms and a relatively short duration? |
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Definition
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Term
This type of infection can continue for years or even life |
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Definition
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Term
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Definition
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Term
genes that stimulate cell growth |
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Definition
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Term
Genes with similar DNA to proto-oncogenes that interfere with the cell's own control mechanisms. |
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Definition
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Term
What are most tumors caused by? |
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Definition
Mutations in the host genes that regulate cell growth |
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Term
WHat is an example of a virus that is associated with the development of cancers? |
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Definition
HPV, EBV(epstein barr virus), HHV-8 (they appear to interfere with the function of an important tumor supressor gene) |
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Term
What are the most common viral causes of cancer? |
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Definition
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Term
How can a vaccine prevent cervical cancer? |
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Definition
The vaccine would hopefully cause the individual to build up immunity to the virus HPV, so that it could not cause cancer |
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Term
What are some ways to study animal viruses? |
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Definition
1. innoculate live animals with the virus 2. cell culture (tissue culture) |
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Term
In this type of culture, animal cells are grown in a liquid medium contained in a special screw-capped flask |
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Definition
cell culture (also know as a tissue culture) |
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Term
tissue removed from an animal then processed to get individual cells |
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Definition
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Term
Distinct morphological alterations in infected cells.(cells may change shape, detach from surface, or lyse) |
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Definition
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Term
a distinct region where the site of viral replication is |
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Definition
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Term
What is one of the most precise methods for determining the concentration of animal viruses in a sample? |
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Definition
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Term
How are plaque assays different from animal virus to bacteriophage? |
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Definition
A monolayer of tissue culture cells is the host instead of the broth with bacterial cells in it. |
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Term
How can the viral titer be estimated? |
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Definition
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Term
in this method, several dilutions of the virus preparation are administered to a number of animals, cells, or chick embryos |
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Definition
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Term
What is the titer of the virus? |
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Definition
the dilution at which 50% of the inoculated hosts are infected or killed. |
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Term
How do we measure the titer of the virus? |
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Definition
ID50: Infective dose LD50: Lethal dose |
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Term
WHen red blood cells agglutinate (clump) |
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Definition
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Term
When does hemagglutination occur? |
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Definition
When individual viral particles attach to the surface molecules of multiple red blood cells simultaneously. |
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Term
What does hemagglutination show? |
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Definition
That there is a high concentration of viral particles in the blood |
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