Chromosome

About: Chromosome is a research topic. Over the lifetime, 17538 publications have been published within this topic receiving 660077 citations. The topic is also known as: chromosomes & GO:0005694.

Biochemical evidence of variability in the DNA repeat length in the chromatin of higher eukaryotes.

Abstract: Biochemical evidence is presented which confirms that the DNA repeat length in micrococcal nuclease (spleen endonuclease, nucleate 3'-oligonucleotidohydrolase, EC 3-1-4-7) digests of Chinese hamster ovary chromatin is shorter than that of rat liver chromatin [J.L. Compton, R. Hancock, P. Oudet, and P. Chambon (1976) Eur. J. Biochem., in press]. A survey of available cells has shown that the DNA repeat length of the chromatin of higher eukaryotes varies widely. A value of 196 base pairs was found for cells of all mature tissues, regardless of the source of the tissue, whereas smaller values were found for cells of actively dividing tissues and larger values were found for a genetically inactive cell. Although the DNA repeat length of the chromatin of cells in culture was usually shorter than 196 base pairs, there was no general correlation between the size of the chromatin DNA repeat length and the rate of cell division or the functional state of the cell in culture. Examination of extensive micrococcal nuclease digests suggests that the chromatin subunits of all of the higher eukaryotic cells we have studied contain a core with approximately 140 base pairs of DNA.

Comparative Gene Mapping: A Fine-Scale Survey of Chromosome Rearrangements between Ruminants and Humans

Abstract: A total of 202 genes were cytogenetically mapped to goat chromosomes, multiplying by five the total number of regional gene localizations in domestic ruminants (255). This map encompasses 249 and 173 common anchor loci regularly spaced along human and murine chromosomes, respectively, which makes it possible to perform a genome-wide comparison between three mammalian orders. Twice as many rearrangements as revealed by ZOO-FISH were observed. The average size of conserved fragments could be estimated at 27 and 8 cM with humans and mice, respectively. The position of evolutionary breakpoints often correspond with human chromosome sites known to be vulnerable to rearrangement in neoplasia. Furthermore, 75 microsatellite markers, 30 of which were isolated from gene-containing bacterial artificial chromosomes (BACs), were added to the previous goat genetic map, achieving 88% genome coverage. Finally, 124 microsatellites were cytogenetically mapped, which made it possible to physically anchor and orient all the linkage groups. We believe that this comprehensive map will speed up positional cloning projects in domestic ruminants and clarify some aspects of mammalian chromosomal evolution. [The sequence data described in this paper have been submitted to the GenBank data library under accession nos. G40978‐G41020, AF083170‐AF083184, AF088286, AF08287, AF083401‐AF083406, AF082884, and AF082885.]

Parasexual Approaches to the Genetics of Man

Abstract: SOMATIC CELL GENETIC METHODS Cell Hybridization SCG gene mapping depen�s on parasexual events in cultured somatic cells (1-4). These are cell hybridization (5, 6) and chromosome elimination (7, 8) (see section on chromosome elimination). In cell hybridization (Figure I) cells are fused to form heterokaryons, with nuclei of both types within a single cytoplasm. The heterokaryons may be used for genetic complementation studies (see section on genetic complementation). If the nuclei fuse and the resulting synkaryon divides and proliferates. a hybrid cell population is formed. The human parental cells are normal diploid cells, usually fibrocytes from skin biopsy or leucocytes from peripheral blood. It is important that they possess a well-characterized karyotype and genetic constitution. The nonhuman cells are usually tissue culture-adapted heteroploid rodent cells. The parental cells are mixed together either as substrate (9) or suspension (10) cultures. It may be important to adjust the density and/or ratio of one parental cell type to the other (9, 10) to maximize yield of heterokaryons. Heterokaryons form spontaneously, but only at a low frequency. which de­ pends principally on the cell lines employed. Agents can be added to the parental cell mixtures in order to increase the frequency of heterokaryon formation. The agent most successfully employed is the parainfluenza virus designated

Maintenance of Epstein-Barr virus (EBV) oriP-based episomes requires EBV-encoded nuclear antigen-1 chromosome-binding domains, which can be replaced by high-mobility group-I or histone H1

Abstract: EBV-encoded nuclear antigen-1 (EBNA-1) binding to a cis-acting viral DNA element, oriP, enables plasmids to persist in dividing human cells as multicopy episomes that attach to chromosomes during mitosis. In investigating the significance of EBNA-1 binding to mitotic chromosomes, we identified the basic domains of EBNA-1 within amino acids 1-89 and 323-386 as critical for chromosome binding. In contrast, the EBNA-1 C terminus (amino acids 379-641), which includes the nuclear localization signal and DNA-binding domain, does not associate with mitotic chromosomes or retain oriP plasmid DNA in dividing cell nuclei, but does enable the accumulation of replicated oriP-containing plasmid DNA in transient replication assays. The importance of chromosome association in episome maintenance was evaluated by replacing EBNA-1 amino acids 1-378 with cell proteins that have similar chromosome binding characteristics. High-mobility group-I amino acids 1-90 or histone H1-2 could substitute for EBNA-1 amino acids 1-378 in mediating more efficient accumulation of replicated oriP plasmid, association with mitotic chromosomes, nuclear retention, and long-term episome persistence. These data strongly support the hypothesis that mitotic chromosome association is a critical factor for episome maintenance. The replacement of 60% of EBNA-1 with cell protein is a significant step toward eliminating the need for noncellular protein sequences in the maintenance of episomal DNA in human cells.