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Eur J Hum Genet. 1996;4(3):160-7.

Tetrasomy 18p de novo: parental origin and different mechanisms of formation.

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Department of Medical Genetics, John F. Kennedy Institute, Glostrup, Denmark.

Erratum in

  • Eur J Hum Genet 1996;4(5):291.


We have used eight PCR-based DNA polymorphisms to determine the parental origin and mechanisms of formation in 9 patients with de novo nonmosaic tetrasomy 18p. The 9 patients, 4 girls and 5 boys, had clinical features characteristic of i(18p) syndrome. The supernumerary marker chromosome was identified by fluorescence in situ hybridization (FISH) analysis using centromeric probes and a flow-sorted 18p-specific library. The isochromosome was of maternal origin in all 9 cases. The formation of tetrasomy 18p cannot be explained by a single model. In 6 cases, meiosis II nondisjunction, followed by subsequent postzygotic misdivsion, and in 1 case postzygotic nondisjunction and postzygotic misdivision were the most likely mechanisms of formation. Alternative mechanisms are suggested in the remaining 2 cases.

[Indexed for MEDLINE]

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