1) The clear constricted portion of the chromosome at which the chromatids are joined and by which the chromosome is attached to the spindle during cell division.

2) The point or region on a chromosome to which the spindle attaches during mitosis and meiosis -- called also kinetochore.

3) A centromere is a constricted region of a chromosome that separates it into a short arm (p) and a long arm (q). During cell division, the chromosomes first replicate so that each daughter cell receives a complete set of chromosomes. Following DNA replication, the chromosome consists of two identical structures called sister chromatids, which are joined at the centromere.