Transposons: the jumping genes

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A brief look at transposons, an important element in the study of genetics.

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Transposons: the jumping genes

  1. 1. Transposons<br />the ‘Jumping Genes’<br />Abhranil Das 08MS34<br />Freshman 2009<br />
  2. 2. Introduction<br />Transposons are sections of the genome <br /> that undergo transposition within the <br /> genome of the same cell, which may <br /> cause mutations.<br />Discovered by Barbara McClintock, for<br /> which she was awarded a <br /> Nobel prize in 1983.<br />She observed how transposition in maize<br /> genome affected kernel colour.<br />Transposons are now a hot favourite among biologists in the field of gene manipulation<br />
  3. 3. Types of Transposon<br />Type I: Retrotransposons<br />Copy, Paste, Send to<br />= transcription, reverse transcription, migration<br />They have direct repeats at each end<br />They show similarity with retroviruses like HIV. Mechanism of action also similar, except that transcription step is absent for viruses.<br />Main enzymes required: transcriptase, reverse transcriptase<br />
  4. 4. Action of Retrotransposons<br />
  5. 5. Types of Transposon<br />Type II: DNA-only transposons<br />Cut, Paste<br />= excision, staggered cut at target, ligation, polymerization<br />Have inverted repeats at each end<br />Main enzyme required: transposase<br />No RNA intermediate<br />
  6. 6. Action of DNA-only transposons<br />
  7. 7. Action of DNA-only transposons<br />
  8. 8. Action of DNA-only transposons<br />
  9. 9. Action of DNA-only transposons<br />
  10. 10. Transposons cause target repeats<br />
  11. 11. Insertion Sequences: Self Sufficiency<br />A transposon needs a transposase, an enzyme, for transposition<br />A transposon which contains a sequence coding for such an enzyme is an insertion sequence<br />It does not have to depend on whether the genome of the cell has a sequence elsewhere coding for the transposase enzyme.<br />
  12. 12. Composite Transposons<br />In addition to the IS, they contain other genetic information.<br />This additional DNA is usually at the centre, flanked by the IS sequences on either side.<br />May transpose in various ways<br />
  13. 13. Credits<br />Google Search<br /> http://www.google.com<br />Wikipedia<br />http://en.wikipedia.org/wiki/Transposon<br />Microsoft Word Autoshape and Drawing Canvas tools<br />

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