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33 Cards in this Set

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