- The centrosome is the cellular organelle responsible for organizing spindle fibers during mitosis.
- During cell division, the centrosome duplicates and each one moves to opposite poles of the cell.
- From these centrosomes, spindle fibers, composed of microtubules, extend and attach to the chromosomes at the kinetochores.
- This arrangement ensures the proper segregation of sister chromatids into the two daughter cells.

- In contrast, other organelles such as the Golgi apparatus, endoplasmic reticulum, and mitochondrion have distinct functions unrelated to spindle fiber organization.
- The Golgi apparatus is involved in modifying and packaging proteins, the endoplasmic reticulum in protein and lipid synthesis, and the mitochondrion in ATP production.

Reference: Molecular Biology of the Cell, 6th Edition, Chapter 18: Mitosis and the Cell Cycle, Pages 1032-1045