Isochromosome

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Isochromosome is a term from genetics and describes a malformation of a chromosome , a structural chromosome aberration in which a chromosome has lost one of its arms and this has been replaced by an exact copy of the other arm. Thus the genetic information is lost on the arm that is no longer contained. The presence of an isochromosome in the genetic information can lead to diseases.

The chromosome arm is normally duplicated during the S phase of the cell cycle. During the metaphase of mitosis (or meiosis I or II), the sister chromatids line up along the midline. The affected chromosome aligns perpendicular to its normal position, and when the anaphase begins, the chromosome is separated so that two long and two short arms remain connected. The two chromosomes that are formed are drawn into the two daughter cells through the microtubules. This leads to two cells in which this chromosome has one arm too many or too little.

The cause of this malformation is assumed to be a miscalculation of the centromere in the metaphase . Instead of parallel to the arms, the chromosome separates perpendicular to it, which means that in prophase  I of meiosis no normal chromosomes are formed, but isochromosomes.

A well-known example of an isochromosomal malformation is the Pallister-Killian syndrome with an additional isochromosome 12p. There is also a variant of Turner syndrome and Klinefelter syndrome with an isochromosome.

Individual evidence

  1. ↑ JL Struthers, CD Cuthbert, MM Khalifa: Parental origin of the isochromosome 12p in Pallister-Killian syndrome: molecular analysis of one patient and review of the reported cases. In: American journal of medical genetics. Volume 84, Number 2, May 1999, pp. 111-115, ISSN  0148-7299 . PMID 10323734 .
  2. ↑ M. de Kerdanet, J. Lucas, F. Lemee, M. Lecornu: Turner's syndrome with X-isochromosome and Hashimoto's thyroiditis. In: Clinical endocrinology. Volume 41, Number 5, November 1994, pp. 673-676, ISSN  0300-0664 . PMID 7828358 .
  3. ^ JP Fryns, A. Kleczkowska, O. Steeno: Isochromosome Xq in Klinefelter syndrome. In: American journal of medical genetics. Volume 36, Number 3, July 1990, pp. 365-366, ISSN  0148-7299 . doi : 10.1002 / ajmg.1320360328 . PMID 2400448 .