The prevailing view of the chromosome of higher organisms is characterized by randomness. Genes are believed to be located at random and mutations and most structural rearrangements are likewise supposed to occur at random (1-4). During the last few years the molecular organization of the eukaryotic chromosome has been subject to intensive investigation but the evidence has been mainly on singl...

The centromere plays an essential role in accurate chromosome segregation, and defects in its function lead to aneuploidy and thus cancer. The centromere-specific histone H3 variant CENP-A is proposed to be the epigenetic mark of the centromere, as active centromeres require CENP-A-containing nucleosomes to direct the recruitment of multiple kinetochore proteins. CENP-A K124 ubiquitylation, med...

Inheritance of each chromosome depends upon its centromere. A histone H3 variant, centromere protein A (CENP-A), is essential for epigenetically marking centromere location. We find that CENP-A is quantitatively retained at the centromere upon which it is initially assembled. CENP-C binds to CENP-A nucleosomes and is a prime candidate to stabilize centromeric chromatin. Using purified component...

The kinetochore, an integrated nucleic acid and protein complex, directs chromosome movement during mitosis and meiosis. Chromosome segregation depends upon the coordinated assembly of kinetochore components at the centromere DNA and attachment to the bipolar array of spindle fibers emanating from microtubule-organizing centers. Both kinetochores and spindles have been the focus of recent effor...

Since the first report in 1993, an ectopic centromere, i.e. neocentromere formation, has been reported in more than 100 small supernumerary marker chromosomes (sSMC), in 7 instances of centromere repositioning, and in about a dozen cases with more complex chromosomal rearrangements. Here we report 2 new cases with centromere repositioning and 3 neocentric sSMC consisting exclusively of heteroch...

We analyzed linkage and chromosomal positions of genes in A. lyrata ssp. petraea that are located near the centromere (CEN) regions of A. thaliana, using at least two genes from the short and long arms of each chromosome. In our map, genes from all 10 A. thaliana chromosome arms are also tightly linked in A. lyrata. Genes from the regions on the two sides of CEN5 have distant map localizations ...

HE centromere, a necessary part of all chromosomes, is the region responsible Tfor congression and poleward movement. It is called “kinetochore” by those who wish to emphasize that it is the center of kinetic chromosome activity. This name is also more suitable because the centromere often is far from central in its location. In the following, the name centromere is retained because of its rela...

background: high-energy ionizing radiation is harmful and changes the genetic makeup of dna, which can lead to increased risk of cancer. thus, the exposure of radiation dose should be under control and limited. ionizing radiation might lead to some chromosome aberrations like dicentric. there is a strong relation between the frequency of dicentric chromosome in metaphase, and the received dose....