The primary constriction, called the centromer, is a common feature of chromosomes necessary for cell division. Presence of repetitive sequences in the centromeric regions have been proven to be essential. In humans, and many other species, specific repetitive sequences, called 'Satellites' are characteristic for the centromer in general. Know more at: http://www.creative-bioarray.com/Satellite-Enumeration-XDXZ1-YDYZ3-18D18Z1-Probe-FPNC-11-item-4587.htm