How the directionally asymmetric grip of the kinetochore can promote accuracy during early mitosis and how it might arise from microtubule polarity. (A) After a pair of sister kinetochores initially makes side-attachments, one of them will (by chance) become tip-attached before the other, tracking with tip shortening and exerting elastic pulling forces on its side-attached sister. Left: If the pair is attached incorrectly to microtubules from the same pole, then the side-attached sister will be pulled toward the minus end. Its grip will therefore be weak and it will likely detach. Right: If the pair is attached correctly to microtubules from opposite poles, then the side-attached sister will be pulled toward the plus end. It will therefore have a stronger grip that should allow it to remain attached and achieve proper biorientation at the plus end. (B) Each Ndc80c fibril (light blue) has a globular foot (outlined in black), which binds with a stereospecific “footprint” on the outside surface of the microtubule, and a coiled-coil stalk that emanates from this foot and projects toward the plus end. Right: Pulling a kinetochore toward the plus end aligns its multiple Ndc80c stalks into a parallel configuration, facilitating interactions with Dam1c oligomers and strengthening the overall grip on the microtubule. Because the direction of force is aligned with the stalks, torque on the Ndc80c-microtubule bonds is minimized. Left: Pulling a kinetochore toward the minus end disrupts this organization, weakening its grip. (C) Right: At a plus end, the Ndc80c stalks can all project in parallel past the tip of the microtubule and converge onto the centromeric nucleosome, potentially allowing Dam1c oligomers to organize a cage-like arrangement surrounding the tip (Jenni and Harrison, 2018; Muir et al., 2023) with even higher grip strength. Left: At a minus end, parallel convergence of the stalks is impossible, increasing the torque on the Ndc80c-microtubule bonds and potentially reducing lateral interactions via Dam1c.