Characterization of additional euchromatic material in 9qh+

Journal Article · Thu Sep 01 04:00:00 EDT 1994 · American Journal of Human Genetics

OSTI ID:134595

Klein, V R; Bialer, M G; Macera, M J ^[1]

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1. Long Island College Hospital, Brooklyn, NY (United States); and others

The presence of an extra G-positive band within the 9qh region is regarded as a normal variant. We recently encountered a case which was different than others by the FISH technique but was apparently the same by routine cytogenetic methods. The major differences included duplication of the beta, satellite III DNA and bands 9q13q21.1 without duplication or inversion of alphoid sequences. Through a review of the literature, we suggest that four different types of variants containing an extra G-positive band can be distinguished. We propose mechanisms to explain the simplest origin of these variants. All classes require unequal crossing-over between homologues. Types I, III and IV require two breaks at various positions within the qh region, while for type II, three breaks are required and one parent needs to have an inverted chromosome 9qh. It is hypothesized that the clinical consequences depend upon the size of the G-positive band(s) duplicated and a genetic inactivation mechanism might have some influence during so-called heterochromatinization. The characterization of variant chromosomes by molecular techniques is becoming imperative, because interruption of pregnancy has occurred in some situations in which variant chromosomes were wrongly identified as abnormalities. Consequently, utmost caution should be exercised during prenatal counseling, especially in situations in which variants have originated de novo.

• OSTI ID: 134595
• Report Number(s): CONF-941009--
• Journal Information: American Journal of Human Genetics, Journal Name: American Journal of Human Genetics Journal Issue: Suppl.3 Vol. 55; ISSN AJHGAG; ISSN 0002-9297
• Country of Publication: United States
• Language: English

Related Subjects

55 BIOLOGY AND MEDICINE
BASIC STUDIES
BANDING TECHNIQUES
CHROMOSOMAL ABERRATIONS
CROSSING-OVER
DNA HYBRIDIZATION
FLUORESCENCE
GENES
GENETICS
HETEROCHROMATIN
HUMAN CHROMOSOME 9
SENSITIVITY
SIZE