Five females with duplication of the short arm of one chromosome 9 are reported, one tetrasomic and four trisomic for 9p. The tetrasomy is due to an isochromosome 9p while the trisomies are due in one case to an intrachromosomal duplication present in lymphocytes but not in fibroblasts, two are secondary to translocations with chromosomes 22 and 13 respectively, and one is a mosaic with a cell line with an additional deleted chromosome 9 present in lymphocytes and fibroblasts. This analysis indicates that duplications 9p may result in impairment of ovarian function. The phenotypic differences between trisomy and tetrasomy 9p are discussed.
A ring 12 chromosome was found in a male child with minor phenotypic alterations. No obvious loss of chromosome material was detected. Since there is no other case of a ring 12 in the literature, it was not possible to determine whether the phenotype was due to (invisible) terminal deletions or to karyotypic variation. In lymphocyte cultures 9% of the cells had either no or two rings, but the patient’s RBC had normal activities of the enzymes lactate dehydrogenase B and peptidase B, whose loci are located on the proximal portions of 12p and 12q, respectively. Dicentric rings were found in 37 cells, and all had two active centromeres, in contrast with the relatively frequent finding of latent centromeres in translocated dicentric autosomes. Two latent centromeres were found in one tricentric “rod-shaped” open ring 12, probably derived from a tetracentric ring. It is postulated that latent centromeres are rare in ring chromosomes because, if consistent suppression of centromeres in excess of one took place at each duplication, rings with four, eight, or more centromeres would be formed rather frequently, which is not the case.
Eight patients are reported with a de novo extra inverted duplicated chromosome 15. The abnormal chromosome was considered to be the same in all cases, but its precise delineation remained uncertain and was defined as either 15pter leads to 15q12::15q12 leads to 15pter or 15pter leads to 15q11::15q13 leads to 15pter. Analysis with various techniques of the satellite regions of the bisatellited chromosomes demonstrated maternal derivation in six and paternal derivation in one of the seven families. A non-sister chromatid exchange between the two homologous chromosomes 15 is considered a likely origin of the inv dup(15) in the cases with maternal derivation; in the only case of paternal derivation, however, the abnormal chromosome originated from one single chromosome 15. The clinical findings confirm that patients with inv dup(15) have mental and developmental retardation and are frequently affected by seizures, while severe physical malformations are absent.
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