How does the mitotic spindle ensure that each daughter cell receives a full complement of the genetic material in the cell nucleus

The mitotic spindle attaches to the kinetochores at the centromeres of the chromosomes and then it moves toward the poles of the cell. Thus, sister chromatids are separated simultaneously at their centromeres so that each daughter cell will have the same genetic material as the parent cell (i.e., daughter cells will be genetically identical to the parent cell).

Explanation:  

The mitotic spindle is a structure composed of microtubule proteins whose function is to ensure the correct segregation of the chromosomes during mitosis. During metaphase, microtubules from the mitotic spindle bind to the kinetochore (a protein complex assembled on the centromeric region) in order to align sister chromatids on the metaphase plate. Subsequently, during anaphase, the mitotic spindle moves toward the poles of the cell, thereby sister chromatids are separated from each other. In consequence, each daughter cell will have the same amount of genetic material (i.e., the same number of chromosomes) as the parent cell.

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