Final answer:
Kinetochores form on the centromere, serving as the attachment site for spindle fibers during mitosis and meiosis. Kinetochores are crucial for correct chromosome segregation.
Step-by-step explanation:
Kinetochores form on the centromere, which is option (a) in the question. These are protein complexes that are essential during cell division. During mitosis and meiosis, spindle fibers attach to kinetochores that have assembled on the centromere of sister chromatids. By prometaphase, the spindles that are responsible for separating the chromatids during mitosis emanate from the centrosome, which is option (b) in the reference question about the origin of mitotic spindles. During cell division, the centromere acts as a point of constriction and attachment for kinetochore microtubules, which play a critical role in chromosome movement. This process is integral to ensuring proper segregation of chromosomes.