A reliable technique for staining human chromosomal nucleolar organizers (NOR's) with silver solutions is described. The NOR's can be selectively stained dark brown by silver solutions leaving the chromosome arms unstained and available for counterstaining with orcein or Giemsa dyes. Unequivocal identification of chromosome pairs bearing NOR's can be achieved using fluorescent banding techniques followed by silver staining. The silver staining procedure for NOR's was simplified and standardized through control of the chemical and physical conditions during silver impregnation and developing.

An improved technique for selective silver staining of nucleolar organizer regions in human chromosomes

The fragile site at Xq27 which is associated with X-linked mental retardation with macroorchidism has been studied in 21 retarded males. These males were from 12 families, and studies of nine of the families were possible. Detection of carrier females is difficult, especially with increasing age. The fragile site was demonstrated in only five of 13 obligate carrier females. It is concluded that using present methods, cytogenetic detection of carriers is fairly reliable in females aged less than 20–25 years but unreliable in older females.

Heritable fragile sites on human chromosomes. VI. Characterization of the fragile site at 12q13.

The chromosomal gaps associated with fragile sites at 2q11, 10q23, 11q13, 16q22, 20p11 and Xq27 do not stain with silver nitrate as do NOR regions of the acrocentric chromosomes.

Heritable fragile sites on human chromosomes. IV. Silver staining.

Four cases of partial trisomy 18q are reported and compared to observations from the literature. The phenotype of 18qter trisomy is described and compared to full trisomy 18.

Trisomy 18qter and trisomy mapping of chromosome 18.

In an effort to identify regions on chromosome 18 that may be critical in the appearance of the Edwards syndrome phenotype, we have analyzed six patients with partial duplication of chromosome 18. Four of the patients have duplications involving the distal half of 18q (18q21.1-qter) and are very mildly affected. The remaining two patients have most of 18q (18q12.1-qter) duplicated, are severely affected, and have been diagnosed with Edwards syndrome. We have employed FISH, using DNA probes from a chromosome 18-specific library, for the precise determination of the duplicated material in each of these patients. The clinical features and the extent of the chromosomal duplication in these patients were compared with four previously reported partial trisomy 18 patients, to identify regions of chromosome 18 that may be responsible for certain clinical features of trisomy 18. The comparative analysis confirmed that there is no single region on 18q that is sufficient to produce the trisomy 18 phenotype and identified two regions on 18q that may work in conjunction to produce the Edwards syndrome phenotype. In addition, correlative analysis indicates that duplication of 18q12.3-q22.1 may be associated with more severe mental retardation in trisomy 18 individuals.

Molecular mapping of the Edwards syndrome phenotype to two noncontiguous regions on chromosome 18.

A male infant with a partial trisomy 18 and a 46,XY, --21, t(18;21)(18qter replaced by 18q12::21 p13 replaced by 21 qter) chromosome complement is described. The translocation chromosome is of special interest because it includes the satellites of chromosome 21. This was shown by differential satellite staining with the ammoniacal-silver technique.

https://jmg.bmj.com/content/jmedgenet/13/6/520.full.pdf

G A Barg

Papers

Inclusion of satellites in an 18/21 translocation chromosome shown by ammonical-silver staining (sat-banding) in case of partial trisomy 18.