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.

Assignment of the gene for cystathionine beta-synthase to human chromosome 21 in somatic cell hybrids.

Abstract: Among several established mouse, rat, and Chinese hamster cell lines that were screened for cystathionine β-synthase (CBS) activity, mouse 3T3 and Chinese hamster Don fibroblasts were found to contain no detectable activity. Somatic cell hybrids between human fibroblasts KG-7 with normal CBS activity and Don/a23TK- cells (series XXI) were examined for CBS activity and for human chromosome content. Only chromosome 21 cosegregated with CBS activity. Because the activities measured could represent either Chinese hamster or human gene products, we have prepared a new series of hybrids between Don/a23TK- cells and mutant human fibroblasts from a patient with homocystinuria due to deficiency of functional CBS mRNA. None of these (series XXV) hybrids contained detectable CBS activity, although collectively all human chromosomes were represented. Our results suggest that the human gene for CBS, called CBS, and thus for the most common form of homocystinuria, is located on chromosome 21.

The DNA sequence, annotation and analysis of human chromosome 3

Abstract: After the completion of a draft human genome sequence1, the International Human Genome Sequencing Consortium has proceeded to finish2 and annotate each of the 24 chromosomes comprising the human genome. Here we describe the sequencing and analysis of human chromosome 3, one of the largest human chromosomes. Chromosome 3 comprises just four contigs, one of which currently represents the longest unbroken stretch of finished DNA sequence known so far. The chromosome is remarkable in having the lowest rate of segmental duplication in the genome. It also includes a chemokine receptor gene cluster as well as numerous loci involved in multiple human cancers such as the gene encoding FHIT, which contains the most common constitutive fragile site in the genome, FRA3B3. Using genomic sequence from chimpanzee and rhesus macaque, we were able to characterize the breakpoints defining a large pericentric inversion that occurred some time after the split of Homininae from Ponginae, and propose an evolutionary history of the inversion.

Cloning of 559 potential exons of genes of human chromosome 21 by exon trapping

Abstract: Chromosome 21 represents approximately 1% of the human genome, and its long arm has been estimated to contain 600-1000 genes. A dense linkage map and almost complete physical maps based on yeast artificial chromosomes (YACs) and cosmids have been developed. We have used exon trapping to identify portions of genes from randomly picked chromosome 21-specific cosmids, to contribute to the creation of the transcription (genic) map of this chromosome and the cloning of its genes. A total of 559 different sequences were identified after elimination of false-positive clones and repetitive elements. Among these, exons for 13 of the 30 known chromosome 21 genes have been "trapped." In addition, a considerable number of trapped sequences showed homologies to genes from other species and to human expressed sequence tags (ESTs). One hundred thirty-three trapped sequences were mapped, and every one mapped back to chromosome 21. We estimate that we have identified portions of up to approximately 40% of all genes on chromosome 21. The genic map of chromosome 21 provides a valuable tool for the elucidation of function of the genes and will enhance our understanding of the pathophysiology of Down syndrome and other disorders of chromosome 21 genes.

Genetic mapping of Prm-1, Igl-1, Smst, Mtv-6, Sod-1, and Ets-2 and localization of the Down syndrome region on mouse chromosome 16.

Abstract: Molecular probes were used as markers in the backcross (Czech II X BALB/cPt) X Czech II to determine the positions of six genes on mouse chromosome 16 (MMU 16). The order of the genes mapped is (centromere), protamine-1 (Prm-1), immunoglobulin lambda 1 light chain (Igl-1), preprosomatostatin (Smst), an endogenous mouse mammary tumor virus locus (Mtv-6), and two more distal sequences, superoxide dismutase, cytoplasmic form (Sod-1), and the proto-oncogene sequence Ets-2. The largest recombination frequency between any two adjacent markers is 24 cM, and thus the position of any marker on MMU 16 that is polymorphic between these two strains can be readily determined in this backcross. A region of MMU 16 which corresponds to the Down syndrome region of human chromosome 21 is located near the distal end of the chromosome.