Lec 15 Transposable elements

Lec 15 Transposable elements - Somatic transposable element...

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Somatic transposable element activity in snapdragon
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Feschotte (2002) Nat Rev Genet 3, 329-41 Instability and mobility are hallmarks of transposable elements
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McClintock discovered Ds by identifying resulting chromosome breaks at a specific locus
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Ac can mobilize the excision of Ds, reverting phenotype.
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Ac is autonomous: encodes transposase Ds is nonautonomous: lacks transposase Ds elements move only in the presence of Ac elements
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Ac transposase cuts at terminal inverted repeats TIR TIR
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Transposase makes staggered cut in target DNA and ligates
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Staggered cuts are repaired to generate short direct repeat of target DNA. Length of the staggered cut varies depending on the transposable element family
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Bacterial transposable elements capture antibiotic resistance genes transposase Inverted repeats
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Evolution of antibiotic resistance plasmid containing IS element and gene for streptomycin resistance Sm IS R esistance T ransfer P lasmid (RTF) conjugative plasmid with IS element recombination conjugative R plasmid RTF Sm IS IS plasmid containing IS element and gene for tetracyline resistance IS IS IS Tc Tc IS IS IS Sm Sm resistance to streptomycin resistance to streptomycin and tetracyclin
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Major categories of transposable elements functional transposase nonautonomous autonomous P element (mobile and encodes functional transposase) lacks functional transposase Class 2 DNA transposons: “cut and paste” DNA transposition Class 1 Retrotransposons: “copy and paste” via RNA intermediate Examples: Ac/Ds (corn), P (fly), IS1, Tn3, Tn10 ( E. coli ) LTR non-LTR reverse transcriptase gag gene LTR LTR Ty1 (yeast), copia (fly) reverse transcriptase RNA binding AAAA LINE SINE (nonautonomous) AAAA Alu (human), B1 (mouse) L1 (human), F (fly) TIR TIR
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reverse transcriptase gag gene long terminal repeats Examples Human: HIV retrovirus Yeast: Ty1 element Drosophila: copia RNA transcript RNA polymerase RTase (including RNase H activity) template switching Insert at staggered break in genomic DNA
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This note was uploaded on 07/17/2011 for the course BIO 151 taught by Professor Grinblat during the Summer '08 term at Wisconsin.

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Lec 15 Transposable elements - Somatic transposable element...

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