What is the X in X-mas?
centromere cen·tro·mere (sěn'trə-mēr')
The most condensed and constricted region of a chromosome to which the spindle fiber is attached during mitosis. Also called kinetochore.
The region of the chromosome to which the spindle fiber is attached during cell division (both mitosis and meiosis). The centromere is the constricted point at which the two chromatids forming the chromosome are joined together. See more at meiosis, mitosis.