GDCB 511-4-27-09

GDCB 511-4-27-09 - GDCB 511: 27 April 2009 Transposition:...

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GDCB 511: 27 April 2009 Transposition: Weaver Chapter 23, 743 – 767 23.1 Bacterial Transposons 23.2 Eukaryotic Transposons 23.3 Rearrangement of Immunoglobulin Genes 23.4 Retrotransposons: Retroviruses, Retrotransposons, Group II Introns
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TE class DNA Transp A transposable element moves from one DNA address to another. Originally discovered in maize, transposon s have been found in all kinds of organisms: Bacteria, Plants, Insects, Humans Originally called “Controlling elements” by McClintock; Later called various terms: mobile elements, jumping genes, selfish DNA Transposable Elements
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Insertion sequences are the simplest type of bacterial transposon They contain only the elements necessary for their own transposition Short inverted repeats at their ends At least 2 genes coding for an enzyme that carries out transposition: transposase.
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Prokaryotic element IS10. Transposase has 3 sequential activities: 1) precise excision of IS10 2) staggered cuts (9 bp) at target site 3) ligation of 3’ ends of IS10 to 5’ ends of target Then, cellular polymerase extends target 3’ ends to fill gaps; nicks are ligated. This generates a 9 bp TSD: Target Site Duplication; these are direct repeats flanking the transposon. Generating the TSD: Target Site Duplication
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The term “selfish DNA” implies that insertion sequences and other transposons replicate at the expense of their hosts, providing no value in return. However, some transposons do carry genes that are valuable to their hosts, antibiotic resistance is among most familiar. Antibiotic Resistance and Transposons Donor plasmid has Kan r , harboring transposon Tn3 with Amp r Target plasmid has Tet r After transposition, Tn3 has replicated and there is a copy in target plasmid Target plasmid now confers both Amp r , Tet r .
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This note was uploaded on 03/08/2010 for the course GDCB 511 taught by Professor Yanhaiyin during the Spring '09 term at Iowa State.

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GDCB 511-4-27-09 - GDCB 511: 27 April 2009 Transposition:...

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