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At least 109 records · Page 6Linked to original sources
PubMed2000

Transposition of duplicated chromosomal segment involving fused BCR-ABL gene or ABL oncogene alone in chronic myelocytic leukemia and Ph chromosome-positive acute leukemia with complex karyotypes.

Thirty-six patients with chronic myelocytic leukemia (CML) in the blastic phase were examined by fluorescence in situ hybridization to clarify the mechanisms of progression of the disease. Two of 19 CML patients in the blastic phase (10.5%) had an extra fused BCR-ABL gene on structurally complex chromosome aberrations in addition to the Ph chromosome. Another patient had an extra ABL oncogene on the end of a deleted chromosome, resulting in three copies of the ABL oncogene. These three patients showed additional chromosome aberrations, such as der(12), der(15), and der(18), which differ from the standard karyotypic evolution in the blastic phase. Amplification of the fused BCR-ABL gene or the ABL oncogene seemed to be induced by transposition. These segmental transpositions suggest that these regions have high genetic instability possibly leading to blastic transformation.

Chromosome Aberrations↗
PubMed1984

Localization of the human glucagon gene (GCG) to chromosome segment 2q36----37.

Hybridization of a 3H-labeled bovine glucagon cDNA plasmid to human metaphase chromosomes revealed significant labeling of the distal portion of the long arm of chromosome 2. A large portion (37%) of the cells analyzed exhibited labeling of the 2. A significant percentage (40%) of the labeled sites on the 2 were in segment 2q36----37. Therefore, the human glucagon gene (GCG), was assigned to this segment. Localization of the glucagon gene, whose chromosomal assignment was previously not known, demonstrates the general applicability of in situ hybridization as a powerful gene mapping technique.

Chromosome Mapping↗
PubMed2001

Conserved chromosome segments in Hylobates hoolock revealed by human and H. leucogenys paint probes.

A complete comparative chromosome map of the white-browed gibbon (Hylobates hoolock, 2n = 38), white-cheeked gibbon (Hylobates leucogenys, 2n = 52), and human has been established by hybridising H. leucogenys chromosome-specific paints and human 24-colour paints onto H. hoolock metaphase chromosomes. In the 18 H. hoolock autosomes, we identified 62 conserved segments that showed DNA homology to regions of the 25 H. leucogenys autosomes. Numerous interchromosomal rearrangements differentiate the karyotypes of H. leucogenys and H. hoolock. Only H. hoolock chromosome 10 showed homology to one entire autosome of H. leucogenys. The hybridisation of human 24-colour paints not only confirmed most of the chromosome correspondences between human and H. hoolock established previously but also helped to correct five erroneous assignments and revealed three new segments. Our results demonstrate that the karyotypes of the extant gibbons have arisen mainly through extensive translocation events and that the karyotype of H. hoolock more closely resembles the ancestral karyotype of Hylobates, rather than the karyotype of H. leucogenys.

Animals↗
PubMed2001

Determination of the number of conserved chromosomal segments between species.

Genomic divergence between species can be quantified in terms of the number of chromosomal rearrangements that have occurred in the respective genomes following their divergence from a common ancestor. These rearrangements disrupt the structural similarity between genomes, with each rearrangement producing additional, albeit shorter, conserved segments. Here we propose a simple statistical approach on the basis of the distribution of the number of markers in contiguous sets of autosomal markers (CSAMs) to estimate the number of conserved segments. CSAM identification requires information on the relative locations of orthologous markers in one genome and only the chromosome number on which each marker resides in the other genome. We propose a simple mathematical model that can account for the effect of the nonuniformity of the breakpoints and markers on the observed distribution of the number of markers in different conserved segments. Computer simulations show that the number of CSAMs increases linearly with the number of chromosomal rearrangements under a variety of conditions. Using the CSAM approach, the estimate of the number of conserved segments between human and mouse genomes is 529 +/- 84, with a mean conserved segment length of 2.8 cM. This length is <40% of that currently accepted for human and mouse genomes. This means that the mouse and human genomes have diverged at a rate of approximately 1.15 rearrangements per million years. By contrast, mouse and rat are diverging at a rate of only approximately 0.74 rearrangements per million years.

Animals↗
PubMed2002

The effect of population history on the lengths of ancestral chromosome segments.

An isolated population is a group of individuals who are descended from a founding population who lived some time ago. If the founding individuals are assumed to be noninbred and unrelated, a chromosome sampled from the population can be represented as a mosaic of segments of the original ancestral types. A population in which chromosomes are made up of a few long segments will exhibit linkage disequilibrium due to founder effect over longer distances than a population in which the chromosomes are made up of many short segments. We study the length of intact ancestral segments by obtaining the expected number of junctions (points where DNA of two distinct ancestral types meet) in a chromosome. Assuming random mating, we study analytically the effects of population age, growth patterns, and internal structure on the expected number of junctions in a chromosome. We demonstrate that the type of growth a population has experienced can influence the expected number of junctions, as can population subdivision. These effects are substantial only when population sizes are very small. We also develop an approximation to the variance of the number of junctions and show that the variance is large.

Chromosomes↗
PubMed2000

Loss of expression of the DRR 1 gene at chromosomal segment 3p21.1 in renal cell carcinoma.

Consistent deletion of DNA sequences in chromosomal band 3p21 observed in a variety of human tumors suggests the presence of one or more tumor suppressor genes within this region. Previously, we reported on the construction of two distinct cosmid contigs and our identification of several new genes within 3p21.1. In our search for tumor suppressor genes from this region, we have cloned a gene that we have called DRR 1 (downregulated in renal cell carcinoma). The gene was first mapped to 3p21.1 by fluorescence in situ hybridization analysis. Further analysis of yeast artificial chromosome clones in 3p14.2-p21.1 refined its localization. DRR 1 spans about 10 Kb of genomic DNA with a 3.5-Kb mature transcript. The putative protein encoded by this gene is 144 amino acids and includes a nuclear localization signal and a coiled domain. The gene showed loss of expression in eight of eight renal cell carcinoma cell lines, one of seven ovarian cancer cell lines, one of one cervical cancer cell line, one of one gastric cancer cell line, and one of one non-small-cell lung cancer cell line. Southern blot analysis did not show any altered bands, indicating that gross structural changes or deletions did not cause the loss of expression. This gene was also found to have reduced expression in 23 of 34 paired primary renal cell carcinomas. Mutational analysis detected three polymorphic sites within the gene, but no point mutations were identified in the 34 primary tumors. However, we did detect base substitutions in 4 of 12 cell lines that had undetectable expression of the gene. We also transfected the gene into DRR 1-negative cell lines and observed clear growth retardation. Our results suggest that loss of expression of the DRR 1 gene may play an important role in the development of renal cell carcinoma and possibly other tumors. Genes Chromosomes Cancer 27:1-10, 2000.

Amino Acid Sequence↗
PubMed1984

Lengths of chromosomal segments conserved since divergence of man and mouse.

Linkage relationships of homologous loci in man and mouse were used to estimate the mean length of autosomal segments conserved during evolution. Comparison of the locations of greater than 83 homologous loci revealed 13 conserved segments. Map distances between the outermost markers of these 13 segments are known for the mouse and range from 1 to 24 centimorgans. Methods were developed for using this sample of conserved segments to estimate the mean length of all conserved autosomal segments in the genome. This mean length was estimated to be 8.1 +/- 1.6 centimorgans. Evidence is presented suggesting that chromosomal rearrangements that determine the lengths of these segments are randomly distributed within the genome. The estimated mean length of conserved segments was used to predict the probability that certain loci, such as peptidase-3 and renin, are linked in man given that homologous loci are chi centimorgans apart in the mouse. The mean length of conserved segments was also used to estimate the number of chromosomal rearrangements that have disrupted linkage since divergence of man and mouse. This estimate was shown to be 178 +/- 39 rearrangements.

Animals↗
PubMed1993

Physical delineation of the minimal chromosomal segment encompassing the murine host resistance locus Bcg.

The host resistance locus Bcg determines resistance of mice to infection with intracellular pathogens such as certain species of Mycobacteria, Salmonella typhimurium, and Leishmania donovani. Bcg maps on the proximal portion of mouse chromosome 1, very tightly linked to villin (Vil), with the gene order and intergene distances Tp-1-(1 cM)-D1Mcg105-(0.1 cM)-lambda Mm1C165/Vil/Bcg-(0.2 cM)-lambda Mm1C136-(0.3 cM)-Des-(0.1 cM)-Inha. In an effort to clone genomic sequences overlapping Bcg, we have used pulsed-field gel electrophoresis (PFGE) and fluorescence in situ hybridization to construct a physical map of the 3.9-Mb segment of proximal mouse chromosome 1, near Bcg. In situ hybridization to metaphase mouse chromosomes indicates that the mapped region is within band C5. Physical mapping of the Tp-1-Vil and lambda Mm1C136-Inha intervals was carried out by PFGE analysis, whereas the Vil-Des interval was estimated by in situ hybridization to interphase nuclei. Results of these combined analyses indicate the following locus order and maximal interlocus distances: Tp-1-(1000 kb)-D1Mcg105-(160 kb)-lambda Mm1C165-(180 kb)-Vil-(800 kb)-lambda Mm1C136-(290 kb)-Des-(130 kb)-Inha. Detailed restriction mapping of this region identifies numerous putative CpG islands, suggesting that several transcription units are present in the vicinity of Bcg.

Animals↗
PubMed1994

Detailed deletion mapping of chromosome segment 17q12-21 in sporadic breast tumours.

Linkage studies have indicated that a gene on chromosome arm 17q, designated BRCA1, confers susceptibility to familial breast and ovarian cancer. To investigate the possible involvement of the BRCA1 gene in sporadic breast cancer we have analysed loss of heterozygosity (LOH) in a panel of 100 sporadic primary breast tumours using 10 PCR-based polymorphic markers from 17q12-21. Allele losses were detected in 40 of 100 tumours informative for at least one of the markers analysed. Of these 40 deleted tumours, 27 showed partial or interstitial loss on 17q. The pattern of LOH in the tumours with partial or interstitial LOH revealed three putative distinct deleted regions on 17q12-21. The first lies on the proximal long arm between D17S250 and THRA1; the second one lies between D17S776 and D17S579, the region containing the BRCA1 gene; and the third is telomeric to D17S733. The most frequently deleted region overlaps with the minimal region containing the BRCA1 gene, suggesting that this gene might also be associated with the development or progression of a proportion of sporadic breast tumours.

BRCA1 Protein↗