A cytogenetic survey of an institution for the mentally retarded: I. Chromosome abnormalities

Abstract

A cytogenetic survey of 475 patients in an institution for the mentally retarded is reported. The chromosomes of all patients were studied using both a non‐banding and a G‐banding technique in order to estimate the relative efficiency of the two techniques in detecting structural rearrangements of the chromosomes. A total of 57 patients was found to have a chromosome abnormality, including five with a balanced structural rearrangement. The contribution of chromosome aberrations to the etiology of mental retardation is discussed with special emphasis on the contribution of balanced structural rearrangements.

The incidence patterns of Down syndrome in Qatar

“…The frequency of regular trisomy 21 in the present study was 98.3%. Despite the small number of cases in this study, this figure is consistent with the report from Kuwait (96.2% (8) and near to those from other countries of 94.1 (17), 94.3 (18), 96.9 (19), 95.5 (20) and 94.1% (3) (Table 1) but is higher than some other studies (21, 22). The frequency of DS mosaicism varies from 0 to 4.6% (17, 21).…”

Structural variations in plant genomes

“…However, changes in chromosome numbers and highly abnormal chromosomes could be distinguished. Later, solid-stained chromosomes were used to detect secondary constrictions, satellite-regions and size variations in heterochromatic regions [42]. By using chromosome-banding techniques, more discrete structural variations could be identified in plant genomes.…”

Copy number variation: New insights in genome diversity

“…Large duplications and deletions have been known for some time to be present within the human genome, initially from cytogenetic observations (e.g., Jacobs et al 1959Jacobs et al , 1978Jacobs et al , 1992Edwards et al 1960;Patau et al 1960;Coco and Penchaszadeh 1982), but their frequency was presumed to be low and for the most part directly related either to tandemly repeated genes or to specific genetic disorders (e.g., Lupski 1998;Ji et al 2000;Inoue and Lupski 2002;Stankiewicz and Lupski 2002). In addition, they were often localized to repeat-rich regions such as telomeres, centromeres, and heterochromatin (e.g., Giglio et al 2001).…”