What forms your spindle fibers?

The formation of spindle fibers is primarily associated with centrosomes. During cell division, specifically in mitosis and meiosis, centrosomes play a critical role by organizing microtubules that make up the spindle fibers. These microtubules are essential for the proper separation of chromosomes as they pull the sister chromatids apart during anaphase.

Centrosomes consist of a pair of centrioles and a surrounding pericentriolar material, which helps in nucleating and anchoring microtubules. As cells prepare to divide, centrosomes duplicate and migrate to opposite poles of the cell, constructing the spindle structure necessary for chromosomes to align and segregate efficiently.

In contrast, kinetochores are protein structures that form on the centromeres of chromosomes, serving as attachment points for spindle fibers but do not themselves form the fibers. Sister chromatids are the duplicated chromosomes connected at their centromeres and are what the spindle fibers act upon during division, while "centrales" is not a recognized term in this context and likely refers to centrosomes misspelled, further emphasizing why the correct choice pertains to centrosomes.