Cytogenetic and physical mapping in the region of the X chromosome surrounding the fragile site.

Seven DNA probes have been mapped within the Xq27-Xq28 region using in situ hybridization, in some cases on chromosomes expressing the fragile site to enhance the resolution. To complement these studies and investigate the relationship between genetic, cytogenetic and physical distance some of these probes were used for large scale mapping using pulsed field gels. Physical linkage was demonstrated between two loci, F9 and MCF2, which are separated by less than 270 kb, and a restriction map extending over 1,300 kb has been generated.

Immunoreactive SOD-1 in amniotic fluid, amniotic cells and fibroblasts from trisomy 21 fetus.

Copper superoxide dismutase (Cu-SOD or SOD-1) was measured by radioimmunoassay (RIA) in amniotic cells and fluid as well as in fetal trisomy 21 fibroblasts. The significant increase of the SOD-1 activity observed in amniotic cells and fetal trisomy 21 fibroblasts demonstrates the early physiopathogenic expression of the supernumerary chromosome 21 in affected patients.

Clinical, chromosomal and enzymatic studies in four cases of rearrangements of chromosome 7.

We report here four cases of unbalanced chromosomal rearrangements involving partial monosomies and trisomies of chromosome 7. The quantitative expression of diaphorase 2 (DIA-2), beta-glucuronidase (GUS-beta) and argino-succinate-lyase (ASL) were measured in these patients and compared with controls. The results suggest that the DIA-2 locus is in the band 7p221----q21, the GUS-beta locus in the band 7p22----q21 and the ASL locus in the band 7p221----q22.

Localization by in situ hybridization of the coagulation factor IX gene and of two polymorphic DNA probes with respect to the fragile X site.

The coagulation factor IX gene and two other polymorphic loci corresponding to DNA probes 52 A and St 14 have been previously localized in the q27 to qter region of the human X chromosome. In order to study their localization with respect to the fragile site at Xq27-28, we have hybridized the three DNA probes to metaphase chromosomes of a boy with fragile X mental retardation. We show that probe 52 A is located in the proximal part of the Xq27 band, while the coagulation factor IX gene is on the distal part of this band, but proximal to the fragile site.

Immunoreactive copper-zinc superoxide-dismutase (SOD-1) in mosaic trisomy 21 and normal subjects.

Copper-zinc superoxide-dismutase (SOD-1) (E.C. 1.