Chromosomes characterization

Gene mapping detection of heteromorphisms and determination of parental origin of heteromorphisms Detection of gene mutations Characterization of structural aberrations Identification of marker chromosomes Characterization of tumor cells Chromosome and karyotype evolution Spatial topography of chromosomes... 

The ultimate job of the SAC is to ensure that cells enter anaphase only after all chromosomes have acquired a bipolar (i.e., amphitelic) attachment to the spindle. As described earlier, the checkpoint signal is initiated at kinetochores that either are not attached to the spindle or display a loss of tension. The kineto-chore is composed of many specific proteins that play two crucial roles (1) coordinate attachment to microtubules, and (2) send signals when attachments are incorrect. Kinetochores are assembled by a complicated process at the centromere, a specific region of the chromosome characterized by the presence of nucleotide repeats. Thus, it is the DNA sequence that ultimately determines where the kinetochore will assemble. Centromeric chromatin is also characterized by the presence of a variant histone, CENP-A, which takes the place of histone H3 in the nucleosome core. 

Crissman, H. A. Hhons, G. X. Chromosome characterization using single fluorescent dye. U.S. Patent 5418169,1995. 

The activated CDKl-cyclin B kinase finally phosphor-ylates a large number of proteins most of which are not well characterized, leading to chromosome condensation, nuclear envelope breakdown, spindle assembly, and chromosome segregation. 

In higher eukaiyotes, most of the chromosomal DNA carries 5-methyl-cytidine residues located in CpG sequence motives. There is a close correlation between transcriptional inactivation and methylation. On the other hand, considerable evidence shows that regions of DNA that are actively engaged in transcription lack 5-methyl-cytidine nucleotides in CpG motivs. Hence DNA methylation is a means how cells regulate gene expression. DNA methylation which is catalyzed by DNA methyltransferases is the best characterized epigenetic mechanism. 

In patients with ataxia-telangiectasia, an autosomal recessive disease in humans resulting in the development of cerebellar ataxia and lymphoreticular neoplasms, there appears to exist an increased sensitivity to damage by x-ray. Patients with Fanconi s anemia, an autosomal recessive anemia characterized also by an increased frequency of cancer and by chromosomal instability, probably have defective repair of cross-linking damage. 

Osteopetrosis (marble bone disease), characterized by increased bone density, is due to inability to resorb bone. One form occurs along with renal tubular acidosis and cerebral calcification. It is due to mutations in the gene (located on chromosome 8q22) encoding carbonic anhydrase II (CAII), one of four isozymes of carbonic anhydrase present in human tissues. The reaction catalyzed by carbonic anhydrase is shown below ... 

Gene knockouts were performed by homologous recombination in mice. The enzymes are characterized as neuronal, inducible (macrophage), and endothelial because these were the sites in which they were first identified. However, all three enzymes have been found in other sites, and the neuronal enzyme is also inducible. Each gene has been cloned, and its chromosomal location in humans has been determined. 

In 1990, work was started to characterize the human genome which had been shown to consist of about 3 billion base pairs. The final result was announced in the year 2000. All of the chromosomes have been characterized. The human genome has been shown to contain some 30,000 genes (which are sections of the chromosome which code for specific proteins). Each cell produces the t T)e of proteins needed for it to function. The function of mRNA is to transfer information from the DNA. so as is to fix the limits of the protein needed. The vast majority of the proteins found in living organisms are composed of only 20 different kinds of amino acids, repeated many times and strung together in a particular order. Each type of protein has its own unique sequence of amino acids. This sequence, known as its primary structure, actually... 

QTLs were also detected in tomato introgression lines (domestic tomatoes with single, defined chromosome regions selected from the progeny of a cross with a wild, non-pigmented variety) that correspond to candidate loci for which genes and mutants have been previously characterized. Detected QTLs included the r locus Psy), the Del locus (LcyE), and the B locus. Similar to the tissue-specific expression of maize Yl, the B locus codes a fruit-specific lycopene cyclase associated with higher levels of P-carotene. ... 

The deletion of pelX and of the five major pel genes from the E. chrysanthemi chromosome failed to totally eliminate the capadty for tissue maceration (16). Analysis of the macerated tissue by electrofocusing followed by an activity detection, revealed the presence of a new set of pectate lyases (up to 5 forms). Because of their low activity in synthetic medium, they were described as secondary pectinases. The gene of one secondary endo-pectate lyases, PelL, has been characterized in two E. chrysanthemi strains. The pelL gene of E. 

Suwa Y, WE Olben, LJ Eorney (1996) Characterization of chromosomally encoded 2,4-dichlorophenoxyace-tic acid-a-ketoglutarate dioxygenase from Burkholderia sp. strain RASC. Appl Environ Microbiol 62 2464-2469. 

The enzymes involved in the degradation of phenanthrene by Nocardioides sp. strain KP7 have been characterized. In this strain, the genes are chromosomal, and phdA and phdB encoding the a- and P-subunits of the dioxygenase, phdC and phdD that encode the ferredoxin, and ferredoxin reductase have been cloned and sequenced (Saito et al. 2000). The order of the genes... 

Legouis R., Cohen-Salmon M., Delcastillo I. and Petit C. (1994). Isolation and characterization of the gene responsible for the X-chromosome linked Kallmann syndrome. Biomed Pharm 48, 241-246. 

Flow cytometric evaluation of bone marrow and peripheral blood to characterize the type of leukemia, as well as to detect specific chromosomal rearrangements. The bone marrow at diagnosis usually is hypercellular, with normal hematopoiesis being replaced by leukemic blasts. The presence of greater than 20% blasts in the bone marrow is diagnostic for AML. 

Kohen, R., Metcalf, M. A., Khan, N. etal. (1996). Cloning, characterization and chromosomal localization of a human 5-HT6 serotonin receptor. /. Neurochem., 66, 47-56. 

In each of these studies dozens of transgenic animals were made and characterized. This is necessary because there is considerable individual variability in phenotype, presumably because of different sized transgene concatemers and different chromosomal integration sites. In some foun-... 

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