Centromere
The centromere is a region of a eukaryotic chromosome that connects the two sister chromatids, and where the spindle fibers attach during mitosis. Centromeric DNA is non-coding, highly repetitive DNA found in the centromere region. It is thought to serve structural purposes.
The centromeric DNA is normally in a heterochromatin state, which is probably essential for its function. In the yeast Schizosaccharomyces pombe (and likely in other eukaryotes) the formation of centromeric heterochromatin is connected to RNAi.[1]
See also: Genetics -- Cell biology