A kinetochore is a protein complex found on the centromere of chromosomes (or sister chromatids).

The kinetochore attaches to structures called kinetochore microtubules, originating from two different centrosomes, during mitosis and meiosis; depolymerisation of these microtubules allows entire chromosomes, in meiosis I, or individual sister chromatids, in mitosis or meiosis II, to be separated from one another and towards whichever centrosome their microtubule originated from.

Non-kinetochore microtubules, which link two centrosomes, then polymerise and elongate to further the distance between the centrosomes and thereby pull the chromosomes/chromatids right to the opposite poles of the cell.