Mirror-symmetric duplicated chromosome 21q with minor proximal deletion, and with neocentromere in a child without the classical down syndrome phenotype

G. Barbi, I. Kennerknecht, G. Wöhr, Dimitrios Avramopoulos, G. Karadima, M. B. Petersen

Research output: Contribution to journalArticle

Abstract

We report on a mentally retarded child with multiple minor anomalies and an unusually rearranged chromosome 21. This der(21) chromosome has a deletion of 21p and of proximal 21q, whereas the main portion of 21q is duplicated leading to a mirror-symmetric appearance with the mirror axis at the breakpoint. The centromere is only characterized by a secondary constriction (with a centromeric index of a G chromosome) at an unexpected distal position, but fluorescence in situ hybridization (FISH) with either chromosome specific or with all human centromeres alpha satellite DNA shows no cross hybridization. Thus, the marker chromosome represents a further example of an 'analphoid marker with neocentromere.' Molecular analysis using polymorphic markers on chromosome 21 verified a very small monosomic segment of the proximal long arm of chromosome 21, and additionally trisomy of the remaining distal segment. Although trisomic for almost the entire 21q arm, our patient shows no classical Down syndrome phenotype, but only a few minor anomalies found in trisomy 21 and in monosomy of proximal 21q, respectively. (C) 2000 Wiley-Liss, Inc.

Original languageEnglish (US)
Pages (from-to)116-122
Number of pages7
JournalAmerican Journal of Medical Genetics
Volume91
Issue number2
DOIs
StatePublished - 2000
Externally publishedYes

Fingerprint

Chromosomes, Human, Pair 21
Down Syndrome
Chromosomes
Phenotype
Centromere
Chromosomes, Human, 21-22 and Y
Satellite DNA
Monosomy
Mentally Disabled Persons
Trisomy
Fluorescence In Situ Hybridization
Genetic Markers
Constriction

Keywords

  • Analphoid marker chromosome
  • Microdissection
  • Monosomy 21
  • Neocentromere
  • Trisomy 21

ASJC Scopus subject areas

  • Genetics(clinical)

Cite this

Mirror-symmetric duplicated chromosome 21q with minor proximal deletion, and with neocentromere in a child without the classical down syndrome phenotype. / Barbi, G.; Kennerknecht, I.; Wöhr, G.; Avramopoulos, Dimitrios; Karadima, G.; Petersen, M. B.

In: American Journal of Medical Genetics, Vol. 91, No. 2, 2000, p. 116-122.

Research output: Contribution to journalArticle

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AU - Kennerknecht, I.

AU - Wöhr, G.

AU - Avramopoulos, Dimitrios

AU - Karadima, G.

AU - Petersen, M. B.

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AB - We report on a mentally retarded child with multiple minor anomalies and an unusually rearranged chromosome 21. This der(21) chromosome has a deletion of 21p and of proximal 21q, whereas the main portion of 21q is duplicated leading to a mirror-symmetric appearance with the mirror axis at the breakpoint. The centromere is only characterized by a secondary constriction (with a centromeric index of a G chromosome) at an unexpected distal position, but fluorescence in situ hybridization (FISH) with either chromosome specific or with all human centromeres alpha satellite DNA shows no cross hybridization. Thus, the marker chromosome represents a further example of an 'analphoid marker with neocentromere.' Molecular analysis using polymorphic markers on chromosome 21 verified a very small monosomic segment of the proximal long arm of chromosome 21, and additionally trisomy of the remaining distal segment. Although trisomic for almost the entire 21q arm, our patient shows no classical Down syndrome phenotype, but only a few minor anomalies found in trisomy 21 and in monosomy of proximal 21q, respectively. (C) 2000 Wiley-Liss, Inc.

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