Duplication of euchromatin without phenotypic effects: a variant of chromosome 16.

A family with an unusual variant of chromosome 16 is presented. The mother and son both with additional material present in the short arm of chromosome 16 adjacent to the centromere are phenotypically normal. The extra C-band negative region has been shown not to be composed of alpha satellite DNA. The literature regarding other familial cases of what appears to be the same variant of chromosome 16 is reviewed.

Human delta-aminolevulinate dehydratase: chromosomal localization to 9q34 by in situ hybridization.

The structural gene for human delta-aminolevulinate dehydratase (ALA-D) has been localized to chromosomal region 9q34 by in situ hybridization using a [125I]-labeled human delta-aminolevulinate dehydratase cDNA. Of the 150 silver grains analyzed, 25% were localized to chromosome 9q, while 12% and 8% were on chromosomes 1p and 13q, respectively. The single chromosomal region q34 had over 90% of the total grains observed on chromosome 9. In contrast, the grains on chromosomes 1p and 13q were dispersed, consistent with the absence of any human ALA-D pseudogenes. Southern blot analysis of somatic cell hybrids informative for ALA-D (Wang et al. 1985) also was consistent and supported the finding of only one locus for this heme biosynthetic enzyme.

Retinoblastoma, chromosome abnormalities and oncogene expression.

Recurrent chromosomal abnormalities in retinoblastomas involve numbers 13, 1, and 6, as well as homogeneously staining regions (HSR) and double minutes (DMS). Evidence suggesting that chromosome 13 contains a gene responsible for tumorigenesis has already been presented. We postulate that the genetic changes resulting from abnormalities of chromosomes 1 and 6 and the HSR/DMS provide a selective growth advantage to cells in which they occur. Support for this hypothesis, as it relates to the HSR/DMS and oncogene amplification, is discussed.

Y-chromosome length heteromorphisms in Delhi infants.

One hundred and seventy normal male infants from Delhi were studied using the CBG technique to estimate Y-chromosome length heteromorphisms. The median class in Y/F [Y/F = total length of the Y chromosome/average total length of the F group chromosomes (19 and 20)] distribution was 0.75-0.79. The Y/F index in infants varied from 0.60 to 1.16 with a mean of 0.81 and a standard deviation of 0.09. A high incidence for very small (53.5 percent) and small (41.2 percent) categories of Y-chromosome length heteromorphisms was observed. Data were compared with other available reports; also possible mechanisms of the Y-chromosome length heteromorphisms and their role in ethnic/racial variation as well as in developmental disturbances are discussed. It is suggested there may be a need to redefine the long and short Y chromosome in a given population while studying different clinical disorders.

Primitive neuroectodermal tumor cell lines: chromosomal analysis of five cases.

A cytogenetic analysis of primitive neuroectodermal tumor (PNET) cell lines was undertaken. PNET are presumed to be embryologically related to, but clinically and histologically distinct from, other tumors of neuroectodermal origin, including neuroblastoma and retinoblastoma. No single chromosome abnormality was found in all five of the tumors studied. In three of the five cases, however, additional 1q material [either as extra chromosome #1 or i(1q)] was found in all cells, and in two of the five, monosomy 13 was noted in all cells; the possible significance of these findings is discussed.

Chromosomal abnormalities in human retinoblastoma. A review.

In part because of an association between the tumor and the constitutional chromosome 13q deletion syndrome and the finding of 13q deletions or monosomy 13 in retinoblastoma cells from individuals with normal constitutional karyotypes, chromosome 13q is postulated to contain a gene responsible for tumorigenesis in retinoblastoma. A review of the cytogenetics of retinoblastoma (incorporating an analysis of five previously unpublished cases and 77 cases from the literature) revealed recurrent abnormalities (in addition to those involving number 13, 21% of cases) that included: additional copies of 1q material (44%), isochromosome (6p) (45%), monosomy 16 (18%), marker 1p+ (13%), and homogeneously staining regions and double minutes (9%). Possible roles for these chromosome abnormalities in tumor development are discussed.

Chromosomal heteromorphisms in Delhi infants. III. Qualitative analysis of C-band inversion heteromorphisms of chromosomes 1, 9, and 16.

Qualitative analysis of C-band heteromorphisms was carried out in 200 infants (100 males and 100 females) in Delhi, India. Partial inversions minor and half inversions were observed as modal levels for chromosomes 1 and 9 in both sexes. No chromosome 16 with a C-band inversion was observed in the present investigation. A significantly higher incidence of percent inversions for chromosomes 1 and 9 was observed in males than in females. The frequency of heterozygous inversion level combinations for chromosome pairs 1 and 9 were remarkably higher than homozygous combinations both in males and females. Our results are compared with the other reported studies, and the possible role of these heteromorphisms in ethnic/racial variation and in developmental disturbances are discussed.

A cytogenetic study of embryonal rhabdomyosarcoma.

In the cytogenetic analysis of an embryonal rhabdomyosarcoma after short-term culture, individual cells were found to contain multiple copies of chromosomes #2, #6, #8, #12, #13, #18, #20 and #21, and del(1)(:p21----qter). The tumor was hypotriploid (mode, 56 chromosomes). The relationship between these findings and published reports of karyotypes from rhabdomyosarcoma is discussed.

Human chromosomal heteromorphisms in Delhi newborns. IV. Inter-relationship between C-band size and inversion heteromorphisms.

The inter-relationship of C-band size and inversion heteromorphisms was studied in 200 Delhi normal newborns (100 males and 100 females). A significant correlation between size and inversion heteromorphisms in males (r = 0.97) and females (r = 0.98) was observed. The results suggested that the larger the size of the C-band regions so the higher was the incidence of inversion.

Human chromosomal heteromorphisms in Delhi newborns. II. Analysis of C-band size heteromorphisms in chromosomes 1, 9 and 16.

Quantitative analysis of C-band size heteromorphisms in chromosomes 1,9 and 16 was carried out in 200 Delhi newborns (100 males and 100 females). The percent size heteromorphisms for chromosomes 1,9 and 16 showed nonsignificant differences between the sexes. Homozygous size level combinations showed higher incidence than the heterozygous combinations for all the three chromosome pairs studied in both sexes. Our results are compared with other reported studies and the possible role of these heteromorphisms in ethnic/racial variation and in developmental disturbances is discussed.