Name the event during cell division that results in the gain or loss of chromosome.

Explanation

**Step-by-Step Solution:**

1. **Understanding Cell Division**: Cell division is the process by which a parent cell divides into two daughter cells. This process involves several stages, including metaphase and anaphase.

2. **Metaphase**: During metaphase, chromosomes align in a straight line at the cell's equatorial plane. This alignment is crucial for the proper segregation of chromosomes.

3. **Anaphase**: Following metaphase, the cell enters anaphase, where sister chromatids are supposed to separate and move towards opposite poles of the cell.

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