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Title Molecular topography of the secondary constriction region (qh) of human chromosome 9 with an unusual euchromatic band
Creator/Author Verma, R.S. ; Luk, S. ; Brennan, J.P. ; Mathews, T. ; Conte, R.A. ; Macera, M.J. (State Univ. of New York Health Science Center, Brooklyn (United States))
Publication Date1993 May 01
OSTI IdentifierOSTI ID: 6281626
Other Number(s)ISSN0002-9297; CODEN: AJHGAG
Resource TypeJournal Article
Resource RelationAmerican Journal of Human Genetics ; Vol/Issue: 52:5
Subject550400 -- Genetics; CHROMOSOMAL ABERRATIONS-- ORIGIN;HUMAN CHROMOSOMES-- CHROMOSOMAL ABERRATIONS; BANDING TECHNIQUES;CROSSING-OVER;DNA HYBRIDIZATION;FLUORESCENCE;HETEROCHROMATIN;MEIOSIS
Related SubjectCELL DIVISION;CHROMATIN;CHROMOSOMES;CYTOLOGICAL TECHNIQUES;HYBRIDIZATION;LUMINESCENCE;MUTATIONS
Description/Abstract Heterochromatin confined to pericentromeric (c) and secondary constriction (qh) regions plays a major role in morphological variation of chromosome 9, because of its size and affinity for pericentric inversion.^Consequently, pairing at pachytene may lead to some disturbances between homologous chromosomes having such extreme variations and may result in abnormalities involving bands adjacent to the qh region.^The authors encountered such a case, where a G-positive band has originated de nova, suggesting a maternal origin from the chromosome 9 that has had a complete pericentric inversion.^In previously reported cases, the presence of an extra G-positive band within the 9qh region has been familial, and in the majority of those cases it was not associated with any clinical consequences.^Therefore, this anomaly has been referred to as a [open quotes]rare[close quotes] variant.^The qh region consists of a mixture of various tandemly repeated DNA sequences, and routine banding techniques have failed to characterize the origin of this extra genetic material.^By the chromosome in situ suppression hybridization technique using whole chromosome paint, the probe annealed with the extra G-band, suggesting a euchromatic origin from chromosome 9, presumably band p12.^By the fluorescence in situ hybridization technique using alpha- and beta-satellite probes, the dicentric nature was further revealed, supporting the concept of unequal crossing-over during maternal meiosis I, which could account for a duplication of the h region.^The G-positive band most likely became genetically inert when it was sandwiched between two blocks of heterochromatin, resulting in a phenotypically normal child.^Therefore, an earlier hypothesis, suggesting its origin from heterochromatin through so-called euchromatinization, is refuted here.^If the proband`s progeny inherit this chromosome, it shall be envisaged as a rare familial variant whose clinical consequences remain obscure.^52 refs., 3 figs.
Country of PublicationUnited States
LanguageEnglish
FormatPages: 981-986
System Entry Date2001 May 13

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