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Inversion polymorphisms and non-contiguous terminal deletions: the cause and the (unpredicted) effect of our genome architecture
  1. R Ciccone1,
  2. T Mattina2,
  3. R Giorda3,
  4. M C Bonaglia3,
  5. M Rocchi4,
  6. T Pramparo1,
  7. O Zuffardi5
  1. 1Biologia Generale e Genetica Medica, University of Pavia, Pavia, Italy
  2. 2Divisione di Genetica Medica, Dip. di Pediatria, University of Catania, Catania, Italy
  3. 3IRCCS “E Medea”, Bosisio Parini, Italy
  4. 4Dip. di Genetica e Microbiologia, University of Bari, Bari, Italy
  5. 5Biologia Generale e Genetica Medica, University of Pavia and IRCCS Policlinico San Matteo, Pavia, Italy
  1. Correspondence to:
 Professor Orsetta Zuffardi
 University of Pavia, Dipartimento di Patologia Umana ed Ereditaria, Via Forlanini 14, 27100 Pavia, Italy; zuffardi{at}


Molecular definition at the BAC level of an 8p dicentric chromosome and an 8p deleted chromosome is reported in a patient with two different cell lines. The dicentric, which differed from that generating the recurrent inv dup del(8p) for the location of its break point, originated during the paternal meiosis on the background of the classical 8p23.1 inversion polymorphism. The breakage of this dicentric gave rise to the 8p deleted chromosome which, as a result of the inversion, had two non-contiguous deletions. These findings confirm previous data on 1p distal deletions, showing that at least some of the deletions stem from the breakage of dicentric chromosomes. They suggest that non-contiguous deletions may be frequent among distal deletions. This type of rearrangement can easily be overlooked when two contiguous clones, one absent and the other present by FISH analysis, are taken as boundaries of the deletion break point; in this case only high resolution array-CGH will reveal their real frequency. The definition of such non-contiguous distal deletions is relevant for phenotype/karyotype correlations. There are historical examples of blunders caused by overlooking a second non-contiguous deletion. This paper shows how small scale structural variations, such as common polymorphic inversions, may cause complex rearrangements such as terminal deletions.

  • BAC, bacterial artificial chromosome
  • CGH, comparative genomic hybridisation
  • FISH, fluorescent in situ hybridisation
  • LCR, low copy repeat
  • NAHR, non-allelic homologous recombination
  • UCSC, University of California Santa Cruz
  • inversion polymorphism
  • dicentric chromosomes
  • terminal deletions
  • non-contiguous deletions

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  • Conflicts of interest: none declared