Chromosome 21

About: Chromosome 21 is a research topic. Over the lifetime, 4736 publications have been published within this topic receiving 206655 citations. The topic is also known as: chr21 & Homo sapiens chromosome 21.

Genome comparisons reveal a dominant mechanism of chromosome number reduction in grasses and accelerated genome evolution in Triticeae

Abstract: Single-nucleotide polymorphism was used in the construction of an expressed sequence tag map of Aegilops tauschii, the diploid source of the wheat D genome. Comparisons of the map with the rice and sorghum genome sequences revealed 50 inversions and translocations; 2, 8, and 40 were assigned respectively to the rice, sorghum, and Ae. tauschii lineages, showing greatly accelerated genome evolution in the large Triticeae genomes. The reduction of the basic chromosome number from 12 to 7 in the Triticeae has taken place by a process during which an entire chromosome is inserted by its telomeres into a break in the centromeric region of another chromosome. The original centromere–telomere polarity of the chromosome arms is maintained in the new chromosome. An intrachromosomal telomere–telomere fusion resulting in a pericentric translocation of a chromosome segment or an entire arm accompanied or preceded the chromosome insertion in some instances. Insertional dysploidy has been recorded in three grass subfamilies and appears to be the dominant mechanism of basic chromosome number reduction in grasses. A total of 64% and 66% of Ae. tauschii genes were syntenic with sorghum and rice genes, respectively. Synteny was reduced in the vicinity of the termini of modern Ae. tauschii chromosomes but not in the vicinity of the ancient termini embedded in the Ae. tauschii chromosomes, suggesting that the dependence of synteny erosion on gene location along the centromere–telomere axis either evolved recently in the Triticeae phylogenetic lineage or its evolution was recently accelerated.

Specific chromosomal aberrations and amplification of the AIB1 nuclear receptor coactivator gene in pancreatic carcinomas.

Abstract: To screen pancreatic carcinomas for chromosomal aberrations we have applied molecular cytogenetic techniques, including fluorescent in situ hybridization, comparative genomic hybridization, and spectral karyotyping to a series of nine established cell lines. Comparative genomic hybridization revealed recurring chromosomal gains on chromosome arms 3q, 5p, 7p, 8q, 12p, and 20q. Chromosome losses were mapped to chromosome arms 8p, 9p, 17p, 18q, 19p, and chromosome 21. The comparison with comparative genomic hybridization data from primary pancreatic tumors indicates that a specific pattern of chromosomal copy number changes is maintained in cell culture. Metaphase chromosomes from six cell lines were analyzed by spectral karyotyping, a technique that allows one to visualize all chromosomes simultaneously in different colors. Spectral karyotyping identified multiple chromosomal rearrangements, the majority of which were unbalanced. No recurring reciprocal translocation was detected. Cytogenetic aberrations were confirmed using fluorescent in situ hybridization with probes for the MDR gene and the tumor suppressor genes p16 and DCC. Copy number increases on chromosome 20q were validated with a probe specific for the nuclear receptor coactivator AIB1 that maps to chromosome 20q12. Amplification of this gene was identified in six of nine pancreatic cancer cell lines and correlated with increased expression.

Gain of chromosome 17 is the most frequent abnormality detected in neuroblastoma by comparative genomic hybridization.

Abstract: Neuroblastoma behavior is variable and outcome partially depends on genetic factors. However, tumors that lack high-risk factors such as MYCN amplification or 1p deletion may progress, possibly due to other genetic aberrations. Comparative genomic hybridization summarizes DNA copy number abnormalities in a tumor by mapping them to their positions on normal metaphase chromosomes. We analyzed 29 tumors from nearly equal proportions of children with stage I, II, III, IV, and IV-S disease by comparative genomic hybridization. We found two classes of copy number abnormalities: whole chromosome and partial chromosome. Whole chromosome losses were frequent at 11, 14, and X. The most frequent partial chromosome losses were on 1p and 11q. Gains were most frequent on chromosome 17 (72% of cases). The two patterns of gain for this chromosome were whole 17 gain and 17q gain, with 17q21-qter as a minimal common region of gain. Other common gains were on chromosomes 7, 6, and 18. High level amplifications were detected at 2p23-25 (MYCN region), at 4q33-35, and at 6p11-22. Chromosome 17q gains were associated with 1p and/or 11q deletions and advanced stage. The high frequency of chromosome 17 gain and its association with bad prognostic factors suggest an important role for this chromosome in the development of neuroblastoma.

Beta amyloid gene duplication in Alzheimer's disease and karyotypically normal Down syndrome.

Abstract: With the recently cloned complementary DNA probe, lambda Am4 for the chromosome 21 gene encoding brain amyloid polypeptide (beta amyloid protein) of Alzheimer's disease, leukocyte DNA from three patients with sporadic Alzheimer's disease and two patients with karyotypically normal Down syndrome was found to contain three copies of this gene. Because a small region of chromosome 21 containing the ets-2 gene is duplicated in patients with Alzheimer's disease, as well as in karyotypically normal Down syndrome, duplication of a subsection of the critical segment of chromosome 21 that is duplicated in Down syndrome may be the genetic defect in Alzheimer's disease.