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33 Cards in this Set
- Front
- Back
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Examples of genetic diversity via horizontal gene transfer.
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Conjugation, Transformation, Transduction
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Conjugation in gram negative cells.
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it depends on specialized (conjugative) plasmids that can transfer themselves from one cell into another (often unrelated genetically). Using a sex pilus.
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In conjugation, some can transfer themselves from bacteria to...
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eukaryotic cells. Ti plasmid is transferred from agrobacteria to plant cells.
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R plasmids transfer...
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antibiotic resistance genes as well.
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Many plasmids carry virulence genes that...
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confer the ability to cause disease.
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Gram positive cells go through conjugation, but..
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the details are different than gram negative.
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Explain how the sex pilus attaches.
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The sex pilus (F pilus) from F+ cellattaches to the F- cell and reels it in.
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in conjugation, SS-DNA is synthesized from....
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the oriTon F plasmid and moves to F- cell via Type IV secretion system. It then is replicated and circularizes. This makes 2 F+ cells.
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In the type IV secretion system, protein are encoded in the ____ operon with ___ genes on the F plasmid. _____ provides the energy.
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tra; 28; ATP
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Both Gram + and - can use
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natural transformation in DNA uptake system.
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In natural transformation...
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DS-DNA binds to the receptor; SS-DNA enters the cell, hybridizes with chromosome and is incoporated via nonreciprocal recombination (must be genetically related to recipient---->only way it works).
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In some species such as H influenzae...
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only a few specific DNA sequences bind to the receptor.
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Transduction is mediated by...
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a bacteriophage (either virulent/lytic, or temperate/lysogenic).
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Temperate phage may....
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go through several lytic cycles before lysogenize.
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Explain the lysogenic cycle.
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The phage is injected into a cell. It then works itself into the chromosome. The phage is now called a prophage. It then makes multiple copies of the cell, and once the prophage is triggered, all the cells undergo a lytic stage.
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When does induction of the prophage occur?
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In response to environmental factors or DNA damage.
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Generalized transduction occurs during...
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the lytic cycle when phage construct heads and tails as separate structures and then reel the DNA up into the heads.
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Rarely, instead of phage DNA getting packaged...
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host DNA gets packaged (1-2%) into transducing phage.
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Transducing phage DNA can be...
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introduced into another cell and incorporated via homologous recombination.
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Transduced DNA is....
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random.
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Specialized transduction occurs only...
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with temperate bacteriophage during the end of the lysogenic cycle.
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In specialized transduction, very infrequently, prophage excision...
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carries part of the adjacent host DNA and this DNA is packaged and injected into a new host.
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Transducing phage may be...
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infectious.
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Transposable elements (transposons) occur in...
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both Bacteria and Archaea; can be found on chromosomes, phage or plasmids; are able to jump around between segments of DNA; autoregulated.
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Insertion sequences (ISs) contain..
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inverted repeats (IRs) flanking transposase genes; they are also numbered.
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Composite transposons (Tn) contain..
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auxilary genes (often toxins or antibiotic resistance) flanked by ISs.
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Replicative transposon has...
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resolvase gene.
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Some transposons completely excise when they...
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jump. This is the cut and paste machanism of transposons. (leave behind just the direct repeats)
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What is the replicative mechanism of transposition?
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when some composite transposons contain resolvase genes that encode proteins that replicate the transposon that moves.
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Tn3: size & genetic marker.
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4,957; ampicillin resistance
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Tn501: size & genetic marker.
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8,200; mercury resistance
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Tn1681: size & genetic marker.
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2,061; Heat-stable enterotoxin
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Tn2901: size & genetic marker.
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11,000; arginine biosynthesis.
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