a specialized condensed region of a chromosomes that appears during mitosis where the chromatids are held together to form an X shape.

A notch in the length of a chromosome

The constricted portion of the chromosome at which the chromatids are joined and by which chromosome is attached to the spindle during cell division. See this in the diagram of cell division shown above.

Constricted region where sister chromatids are attached in mitotic chromosomes. The centromere is generally flanked by repetitive DNA sequences and it is late to replicate. The centromere is an A-T region of about 130 bp. It binds several proteins with high affinity to form the kinetochore which is the anchor for the mitotic spindle.