Tetrasomy 18p de novo: parental origin and different mechanisms of formation.
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.
Bugge
M
M
Department of Medical Genetics, John F. Kennedy Institute, Glostrup, Denmark.
Blennow
E
E
Friedrich
U
U
Petersen
M B
MB
Pedeutour
F
F
Tsezou
A
A
Orum
A
A
Hermann
S
S
Lyngbye
T
T
Sarri
C
C
Avramopoulos
D
D
Kitsiou
S
S
Lambert
J C
JC
Guzda
M
M
Tommerup
N
N
Brøndum-Nielsen
K
K
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