What Moves the Chromatids During Mitosis?

Sister chromatids move because kinetochore microtubules attach to them during metaphase and shorten during anaphase. As they shorten, the mirocrotubules pull each sister chromatid toward an opposite pole of the cell, ensuring that only one copy of DNA is present in each daughter cell.

Mitosis begins after interphase ends, and the nuclear material of the cell is replicated. The first phase of mitosis is called prophase, during which the DNA that has been replicated condenses into an X-shaped body. The next phase is called prometaphase; during this stage, the nuclear membrane breaks down into vesicles, which allows microtubules to invade the nuclear space of the cell.

Metaphase follows prometaphase, when the chromosomes begin to align at the equator of the cell and the microtubules from each pole attach to the kinetochores of the chromosomes. Anaphase is the next phase, and it marks the separation of the sister chromatids. It is divided into two parts: anaphase A, during which the kinetochore microtubules shorten and pull the sister chromatids toward each separate pole, and anaphase B, during which astral microtubules separate the poles further apart, separating the sister chromatids even more.

The last two phases are telophase and cytokinesis. In telophase, the mitotic spindle disintegrates after the chromatids arrive at their separate poles. During cytokinesis, the cell splits in half after the creation of a cleavage furrow, which bisects the cell, marking the end of cell division and the creation of two daughter cells.