Insertion sequence

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Insertion sequences (insertion sequence or IS element) are short, mobile pieces of DNA in bacteria , archaea and some bacteriophages with inverted repeats that can be inserted into DNA . Insertion sequences are a form of self-serving DNA .

properties

Insertion sequences

  • have a size of approx. 800-2000  bp
  • are transposed once every 10 million cell divisions (i.e. installed offset)
  • if they are incorporated into structural genes at integration sites ( palindromes ) , they inhibit their function
  • usually consist of repetitions in opposite directions at the ends and open reading frames inside
  • code their "own" transposase for integration into the genome (they are therefore a type of DNA transposons )

During transposition, the integration site is cut offset by a few base pairs (by the transposase), the inverted repeats of the IS element are attached and the gaps that arise at the interfaces are closed by general DNA synthesis.

The IS elements have a mutagenic effect , as they usually destroy the function of the gene when they are inserted into an open reading frame by shifting the reading frame (frame shift mutation) . It is also possible that the plasmid is inserted into the bacterial chromosome via homologous sequences on a plasmid and the IS elements in the bacterial chromosome.

The inverted repeats (IR) flank the area coding for the transposase on both sides. They consist of not necessarily identical 10 to 50 bp long DNA sequences.

swell

  • Katharina Munk (Ed.): Pocket textbook Biology: Microbiology. Thieme, Stuttgart 2008, ISBN 978-3-13-144861-3 , pp. 238-239.
  • Michael T. Madigan, John M. Martinko, David A. Stahl, David P. Clark: Brock Biology of Microorganisms. 13th edition. Addison-Wesley Longman, Amsterdam, ISBN 978-0321735515 , pp. 286-287.