title: Tetrasomy 18p de novo: parental origin and different mechanisms of formation.
abstract: 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.
authors.affiliation: Department of Medical Genetics, John F. Kennedy Institute, Glostrup, Denmark.
authors.forename: M
authors.initials: M
authors.lastname: Bugge
authors.forename: E
authors.initials: E
authors.lastname: Blennow
authors.forename: U
authors.initials: U
authors.lastname: Friedrich
authors.forename: M B
authors.initials: MB
authors.lastname: Petersen
authors.forename: F
authors.initials: F
authors.lastname: Pedeutour
authors.forename: A
authors.initials: A
authors.lastname: Tsezou
authors.forename: A
authors.initials: A
authors.lastname: Orum
authors.forename: S
authors.initials: S
authors.lastname: Hermann
authors.forename: T
authors.initials: T
authors.lastname: Lyngbye
authors.forename: C
authors.initials: C
authors.lastname: Sarri
authors.forename: D
authors.initials: D
authors.lastname: Avramopoulos
authors.forename: S
authors.initials: S
authors.lastname: Kitsiou
authors.forename: J C
authors.initials: JC
authors.lastname: Lambert
authors.forename: M
authors.initials: M
authors.lastname: Guzda
authors.forename: N
authors.initials: N
authors.lastname: Tommerup
authors.forename: K
authors.initials: K
authors.lastname: Brøndum-Nielsen
mesh_terms: D000293:Adolescent; D000328:Adult; D000782:Aneuploidy; D002648:Child; D002675:Child, Preschool; D002874:Chromosome Mapping; D002887:Chromosomes, Human, Pair 18; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007223:Infant; D008297:Male