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.

Chromosomal localization of the human c-fms oncogene

Abstract: A molecular probe was prepared with specificity for the human cellular homologue of transforming sequences represented within the McDonough strain of feline sarcoma virus (v-fms). By analysis of a series of mouse-human somatic cell hybrids containing variable complements of human chromosomes it was possible to assign this human oncogene, designated c-fms, to chromosome 5. Regional localization of c-fms to band q34 on chromosome 5 was accomplished by analysis of Chinese hamster-human cell hybrids containing as their only human components, terminal and interstitial deleted forms of chromosome 5. The localization of c-fms to chromosome 5 (q34) is of interest in view of reports of a specific, apparently interstitial, deletion involving approximately two thirds of the q arm of chromosome 5 in acute myelogenous leukemia cells.

Amplification of a long terminal repeat-like element on the Y chromosome of the platyfish, Xiphophorus maculatus.

Abstract: The platyfish (Xiphophorus maculatus), in which sex chromosomes are evident from stable and predictable inheritance of sex, is one of the best-studied lower vertebrates with respect to sex determination. In order to identify the structural equivalent for this in the karyotype, which does not contain heteromorphic pairs of chromosomes, two sex-linked molecular probes were used for fluorescent in situ hybridization analysis. One probe, derived from the melanoma oncogene locus ONC-Xmrk, stained both the X and the Y chromosome. This cytogenetic analysis mapped the sex-determining locus to the subtelomeric region of a medium-sized telocentric chromosome. Another probe, a repetitive element (XIR), specifically labeled the Y chromosome in metaphase spreads and in interphase nuclei. The sex chromosomes of X. maculatus can be considered to be at an early stage of evolution of gonosomes. Expansion of the XIR repeat is obviously one of the earliest of the molecular events that lead to divergence of the Y chromosome and recombinational isolation of the sex-determining locus.

Enhanced meiotic recombination on the smallest chromosome of Saccharomyces cerevisiae.

Abstract: Chromosome I is the smallest chromosome in Saccharomyces cerevisiae and contains a DNA molecule that is only 250 kilobases (kb). Approximately 75% of this DNA molecule has been cloned. A restriction map for the entire DNA molecule from chromosome I was determined and most of its genetically mapped genes were located on this physical map. Based on the average rate of recombination (centimorgans/kb) found for other S. cerevisiae chromosomes, the outermost markers on the genetic map of chromosome I were expected to be close to the ends of the DNA molecule. While the rightmost genetic marker was 3 kb from the end, the leftmost marker, CDC24, was located near the middle of the left arm, suggesting that the genetic map would be much longer. To extend the genetic map, a copy of the S. cerevisiae URA3 gene was integrated in the outermost cloned region located 32 kb centromere distal to CDC24, and the genetic map distance between these two genes was determined. The new marker substantially increased the genetic map length of chromosome I. In addition, we determined the relationship between physical and genetic map distance along most of the length of the chromosome. Consistent with the longer genetic map, the average rate of recombination between markers on chromosome I was greater than 50% higher than the average found on other yeast chromosomes. Owing to its small size, it had been estimated that approximately 5% of the chromosome I homologues failed to undergo meiotic recombination. New measurements of the zero-crossover class indicated that the enhanced rate of recombination ensures at least one genetic exchange between virtually every pair of chromosome I homologues.

Physical and genetic mapping of Candida albicans: several genes previously assigned to chromosome 1 map to chromosome R, the rDNA-containing linkage group.

Abstract: Analysis of the karyotypes of multiple Candida albicans isolates by pulsed-field electrophoresis confirms the observation by Lasker et al. of eight chromosomes. The genes previously assigned to chromosome 1 in fact fall into two groups, one (including ADE1, SOR9, and CDC10) is linked to the ribosomal DNA genes on a chromosome called R, whereas the others are found on chromosome 1. Chromosome R varies in electrophoretic mobility among strains, usually running equal to or faster than chromosome 1 but in rare cases running slower than chromosome 1. In strain 1012A, the decreased mobility of one homolog is associated with the very large majority of the rDNA genes being on that homolog; the second homolog, with only a few copies, migrates with chromosome 2. Linkage analysis by using spheroplast fusion confirms the gene assignments made by hybridization to blots of the electrophoretic karyotype. A newly cloned gene, LYS2, hybridizes to chromosome 1.

Genetic dissection of Down syndrome-associated congenital heart defects using a new mouse mapping panel.

Abstract: Down syndrome (DS), caused by trisomy of human chromosome 21 (Hsa21), is the most common cause of congenital heart defects (CHD), yet the genetic and mechanistic causes of these defects remain unknown. To identify dosage-sensitive genes that cause DS phenotypes, including CHD, we used chromosome engineering to generate a mapping panel of 7 mouse strains with partial trisomies of regions of mouse chromosome 16 orthologous to Hsa21. Using high-resolution episcopic microscopy and three-dimensional modeling we show that these strains accurately model DS CHD. Systematic analysis of the 7 strains identified a minimal critical region sufficient to cause CHD when present in 3 copies, and showed that it contained at least two dosage-sensitive loci. Furthermore, two of these new strains model a specific subtype of atrio-ventricular septal defects with exclusive ventricular shunting and demonstrate that, contrary to current hypotheses, these CHD are not due to failure in formation of the dorsal mesenchymal protrusion.