Mitosis is the process of 'divvying up' the genome between dividing cells.
What follows is a simple guide for those unfamiliar with cell division and mitosis. To make this simple, let's imagine a cell with only one chromosome. They are identical copies of one another. Before this cell can divide, it must separate these sister chromatids from one another. Then the cell can replicate its DNA again during interphase and go through mitosis once more.