The centromere (centro- + -mere) is the part of a chromosome that linkssister chromatids. During mitosis, spindle fibers attach to the centromere via the kinetochore.Centromeres were first defined as genetic loci that direct the behavior of chromosomes.Their physical role is to act as the site of assembly of the kinetochore - a highly complex multiprotein structure that is responsible for the actual events of chromosome segregation - i.e. binding microtubules and signalling to the cell cycle machinery when all chromosomes have adopted correct attachments to the spindle, so that it is safe for cell division to proceed to completion and for cells to enter anaphase.