Complete deficiency of constitutive heterochromatin on a human chromosome 9

A healthy normally intelligent man and his two daughters who had mild developmental delay and different malformations were determined to have an acrocentric supernumerary microchromosome (MC). The father and both daughters were noted to be mosaic for the MC, perhaps suggesting mitotic instability of the MC cell line with loss over time. The MC was negative staining on G-banding and showed absence of centromeric heterochromatin on C-banding. A centromere was identified with silver staining; no NORs were identified. The MC approximated the size of the short arm of the Y chromosome and showed cytologic behavior similar to that of a Y chromosome. H-Y antigen and Y-DNA gene probe studies failed to confirm a Yp origin.

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Familial supernumerary microchromosome mosaicism: Phenotypic effects and an attempt at characterization

Chudley

Zheng

Pabello

et al. 1983

Am. J. Med. Genet.

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Inversion‐duplication of bands q13→q21 of human chromosome 9

Luke¹,

Verma²,

PeBenito³

et al. 1991

Am. J. Med. Genet.

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Structural abnormalities involving heterochromatic regions of the human genome are difficult to characterize because these segments are G-band negative by GTG technique, a routinely used procedure in clinical cytogenetic laboratories. Chromosome abnormalities of such cases have gone undetected or were incorrectly characterized because these regions are so-called heteromorphisms or variants. Consequently, much anxiety has been aroused by the confusion between a chromosome abnormality and a normal heteromorphic variant. We report the first documented case with a so-called highly unusual h region of chromosome 9 which is not a variation but a structural rearrangement involving a paracentric inversion and a duplication. The major clinical features were psychomotor retardation, microcephaly, narrow palpebral fissures, renal and genital anomalies, vertebral anomalies, protruding tongue, and learning and behavioral problems. A concise review of variable duplicated segments of 9q is also provided.

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Counterstain-enhanced chromosome banding

Schweizer

1981

Hum Genet

152

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Complete deficiency of constitutive heterochromatin on a human chromosome 9

Cited by 11 publications

References 7 publications

Familial supernumerary microchromosome mosaicism: Phenotypic effects and an attempt at characterization

Familial supernumerary microchromosome mosaicism: Phenotypic effects and an attempt at characterization

Inversion‐duplication of bands q13→q21 of human chromosome 9

Counterstain-enhanced chromosome banding

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