Video narration
How can a cell divide without leaving either new cell short of DNA? Imagine copying a digital file: you make a matching copy before sharing the information. But that's only a comparison. A cell has to physically sort its DNA into two sets. Here's the crucial order: the cell copies its DNA before mitosis begins. So the DNA isn't simply cut in half between the new cells. Mitosis is the division of the nucleus. The copied DNA separates into two matching sets, moving to opposite sides, and a new nucleus forms around each set. The nucleus has divided, but the whole cell has not. Only afterward does the cell split, with one nucleus going into each new cell. That sequence answers the puzzle: copy first, separate the sets, then split the cell. Each new cell receives a full set, with matching genetic information.