What are kinetochores made of?

Microtubules from each centrosome connect to specialized regions in the centromere called kinetochores.

Microtubules tug on the kinetochores, moving the chromosomes back and forth, toward one pole, then the other.

The kinetochore is the protein structure on chromatids where the spindle fibers attach during cell division to pull sister chromatids apart during cell division.

Even the simplest kinetochores consist of more than 19 different proteins including a specialized histone which helps the kinetochore associate with DNA.

There are also motor proteins, including both dynein and kinesin, which generate forces that move chromosomes during
mitosis.

Other proteins monitor the microtubule attachment as well as the tension between sister kinetochores and activate the
spindle checkpoint to arrest the cell cycle when either of these is absent.

Image of a human cell showing microtubules in green, chromosomes (DNA) in blue, and kinetochores in pink.