As a human cell begins division, its 23 chromosomes
duplicate into identical copies that remain joined at a region called the centromere. Here lies the kinetochore, a complicated assembly of proteins that binds to thread-like structures, the microtubules. As mitosis progresses, the kinetochore gives green light to the microtubules to tear the DNA copies apart, towards the new forming cells. “The kinetochore is a beautiful, flawless machine: You almost never lose a chromosome in a normal cell!”, says Musacchio. “We already know the proteins that constitute it, yet important questions about how the kinetochore works are still open: How does it rebuild itself during chromosome replication? How does it bind to the microtubules? And how does it control them?”
Beautiful. Flawless. The kinetochore (from the Greek “motion place”) binds the spindle fibers to the centromere of each chromosome, a spot at the center of a chromosome made for attachment to the spindle. Those who recall the stages of cell division in high school remember that the chromosome pairs all line up in the center of the cell. At metaphase, something “lassos” each sister chromatid (individual member of the pair) at the centromere and exerts force to pull them apart into the daughter cells at anaphase.
What the Max Planck team actually saw was not a random,
Kinetochores are pulling chromosomes
apart into daughter cells every day, in every eukaryotic organism, all
over the world." CEH
