The centromere is a region on a chromosome where sister chromatids are joined together, and where the kinetochore is assembled in order to attach to the mitotic spindle. Centromeres do not have a specific DNA sequence, but do have several unique features including highly repetitive DNA sequences. A recent paper has found that these repetitive sequences are important to generate a fully functional centromere. The authors used a cell line where one chromosome has relocated its centromere, but left the repetitive sequence at the old centromere’s site. Image above shows the chromosomes from this cell line, with zoomed images of the chromosome with the new centromere. A protein called CENP-A (top) labels the new centromere (arrowhead), while a more general centromere label (bottom) is found on both the new and old (asterisk) centromere sites.
Reference: Emily A. Bassett, Stacey Wood, Kevan J. Salimian, Sandya Ajith, Daniel R. Foltz and Ben E. Black, 2010. Originally published in Journal of Cell Bioloy. doi: 10.1083/jcb.201001035. Paper can be found here.
Great blurb about this paper can be found here.