centromere

The centromere is a region on a chromosome that joins two sister chromosomes. The centromere usually contains specific types of DNA sequences which are in higher eukaryotes typically tandem repetitive sequences called satellite DNA. During mitosis the centromere can be identified in particular during the metaphase stage as a constriction at the chromosome. At this centromeric constriction the two mostly identical halves of the chromosome are the sister chromatid.