noun, plural: kinetochores
The kinetochore is a protein structure. It forms at the centromere of every chromosome. Its main function is to bind microtubules of the spindle so that during metaphase the chromosomes would be able to properly align at the metaphase plate prior to anaphase, which is the pulling of chromosomes toward opposite poles of the cell. Thus, the kinetochore is important for the proper chromosome segregation.
In most animal cells, the kinetochore is a disc-like complex forming on the side of every chromatid where spindle fibers would attach to. Thus, a human mitotic chromosome, being comprised of two sister chromatids linked together via a centromere, would have two kinetochores situated in opposite directions at the centromeric region.
The kinetochore is comprised of an inner region (called inner kinetochore) and an outer region (called outer kinetochore). The inner kinetochore is tightly bound to the centromere DNA. The outer kinetochore is the one that interacts with the microtubules. Depending on the species, the number of microtubules attached to the kinetochore varies. In humans, there are about 15 microtubules attach to the kinetochore.
Unlike the outer kinetochore that forms and becomes functional only during mitosis and meiosis, the inner kinetochore persists throughout the cell cycle.
Word origin: Greek khôros (“space”)