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20 Cards in this Set
- Front
- Back
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Evolution of bacteria |
Transduction attacked by bacteriophages change their DNA or carry DNA from one bacterium to another -> altered genotype |
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Bacteriophages |
-viruses infecting bacteria -only contain RNA or DNA not both -early genes: expressed almost immediately encode phage nucleic acid -expression of late genes for particle production -phage particles assemble + cell lysis -plaque formation on colonies |
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dsDNA bacteriophages |
replicate by changing from linear to circular DNA rolling circle phage tails and empty heads are assembled and DNA is cut DNA packed into head, tail attached, cell is lysed |
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Bacteriophage T4 |
icosahedral lytic dsDNA |
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ssDNA bacteriophages replication |
ssDNA is converted to dsDNA dsDNA = replicative form more ssDNA is produced only ssDNA is packed into phage head |
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phi X174 |
icosahedral circular ssDNA 11 proteins due to extensive overlapping of reading frames |
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bacteriophage M13 |
filamentous phage ssDNA specific to F-plasmid containing cells non-lytic subunits are formed by polymerization around DNA during extrusion rolling circle |
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filamentous phage |
variable capsid size circular ssDNA for biotech: plasmid vector, T7 expression system |
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MS2 |
ssRNA for replication + translation icosahedral specific for F plasmid containing cells only 3 proteins: coat, attachment protein + replicase replication: needs RNA directed RNA polymerase release by mechanical damage to membrane |
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binding of phages is receptor specific |
therefore bacteria can become resistant |
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infectious cycle |
1. Adsorption 2. Separation of DNA from coat 3. Viral replication 4. Maturation (assembly of progeny phage particles) 5. release + re-infection |
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scaffolding proteins |
needed for assembly of complex forms removed once assembly is completed |
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three stages of phages |
1. extracellular virions 2. vegetative phage (virulent) 3. prophage |
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vegetative phage lytic pathway |
adsorption + penetration (attachment, injection) transcription + translation + assembly host cell breaks |
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prophage lysogenic |
viral DNA inserted into host DNA viral DNA only replicated when host DNA is replicated viral DNA remains dormant (cell has viral DNA inside with no effect, normal growth) external trigger promotes lytic pathway lambda phage can stay in lysogenic cycle (stable relationship) |
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temperate phage |
has ability to display lysogenic + lytic cycle not obligate lytic |
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P1 phage
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temperate bacteriophage of E.coli
phage genome exists as plasmid inside bacterium |
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generalized transduction |
host DNA accidentally incorporated into phage DNA and carried to new bacterium recombination with bacterial DNA possible |
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specialized transduction |
host DNA is incorporated into phage after lysogenic cycle parts of host DNA are introduced into new phages recombination with new bacterial host DNA possible |
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Cre/loxP System |
specifically genetic engineering of genes Cre-Recombinase finds loxP gene which can be inserted at any point where a gene should be cute out |
