Reassessment of a chromosome 12q + marker by fluorescent in situ hybridization (FISH)

Abstract

We present a case previously described by Jenkins et al. (1983) as atypical Down syndrome (DS). The initial diagnosis was first made on the basis of phenotypic and cytogenetic data. This analysis was supported by studies of superoxide dismutase (SOD1) activity that maps to band 21q22.1. Results from phenotypic, chromosome banding and SODI studies suggested a karyotype of 46,XX,—12, + t(12pter to 12qter::21q21 to 21q22.?2). Using fluorescent in situ hybridization (FISH) for chromosome painting with DNA libraries derived from sorted human chromosomes to stain selectively the chromosomes No. 21 and No. 12, we demonstrate that the marker chromosome 12q+ has no chromosome 21 content but it is derived from chromosome 12.

Chromosome painting using FISH (fluorescence in situ hybridization) with chromosome‐6‐specific library demonstrates the origin of a de novo 6q+ marker chromosome

“…Two previously reported patients with a de nova derivative chromosome with additional chromosomal material were found to have an intrachromosomal duplication after chromosome painting with the corresponding library (Carter et al 1992, Jeziorowska et al 1992. We suggest that this type of marker chromosome often represents duplications, even when this is not apparent from the banding pattern.…”

“…In the form of chromosome painting, chromosome in situ suppression (CISS) hybridization is used with a chromosome-specific DNA library as probe pool (Pinkel et al 1988). This technique can distinguish ("paint") an individual chromosome, and thereby can be used to help characterize structural chromosome aberrations, including unbalanced aberrations with unknown chromosomal material (Viljoen et al 1992, Mangelschots et al 1992, Jeziorowska et al 1992.…”