During which phase of mitosis does the cell nucleus divide?

The cell nucleus divides during telophase, which is the final stage of mitosis. In this phase, the chromosomes reach the opposite poles of the cell and begin to decondense back into chromatin. As the chromosomes loosen, the nuclear envelope re-forms around each set of chromosomes, resulting in two distinct nuclei within the daughter cells. This re-formation of the nuclear envelope signifies the completion of nuclear division and is a crucial step in ensuring that each daughter cell receives the correct genetic material.

In telophase, alongside the division of the nucleus, the cell prepares for the final separation into two distinct cells, often followed by cytokinesis. Other phases of mitosis, such as anaphase and prophase, do not result in the division of the nucleus; rather, they involve the separation and movement of chromosomes and the early organization of structures necessary for division. Interphase, while essential for cell growth and DNA replication, does not involve mitosis at all and therefore does not pertain to the process of nuclear division during the mitotic cycle.