The structure responsible for moving the chromosomes during mitosis is the mitotic spindle , specifically its spindle fibers (microtubules) that attach to chromosomes and pull them apart.

During mitosis, the mitotic spindle forms from microtubules and associated proteins, stretching from one pole of the cell to the other. Spindle fibers attach to each chromosome at a region called the kinetochore on the centromere, then shorten and reorganize to pull sister chromatids toward opposite poles. This coordinated pulling and pushing ensures that each new daughter cell receives the correct set of chromosomes.