At the end of the second phase of mitosis, which event occurs?

• A. The cytoplasm divides
• B. The doubled chromosomes split apart
• C. The nucleus forms
• D. The chromosomes duplicate

Answer: (B)

The key idea here is what happens to the sister chromatids during mitosis. In the phase after metaphase, the spindle fibers shorten and pull the chromatids apart at the centromere. Once separated, each chromatid becomes its own chromosome and is pulled to opposite poles of the cell. This separation of the duplicated genetic material is what happens by the end of that second phase, preparing the cell for the final steps of division.

Cytoplasm division (cytokinesis) happens after mitosis finishes. The nucleus re-forms around each set of chromosomes during the later stage of mitosis (telophase). The chromosomes themselves duplicate earlier, during interphase before mitosis begins.