In the stages of cell division, what occurs during prophase?

During prophase, the key event is that chromosomes condense and become visible. This process marks the beginning of cell division. Prior to prophase, the genetic material exists as loosely arranged chromatin within the nucleus. As prophase progresses, the chromatin fibers coil and shorten, ultimately forming distinct, compact structures known as chromosomes. Each chromosome consists of two sister chromatids joined at a region called the centromere. This condensation is crucial as it allows for the orderly separation of chromosomes later in the subsequent stages of cell division.

In this stage, the nuclear envelope has not yet ruptured, which occurs later during prophase in a subsequent process; rather, the envelope begins to break down as prophase progresses into metaphase. The alignment of chromosomes in the center of the cell occurs during metaphase, where paired chromosomes align along the equatorial plane. Finally, the physical splitting of the cells occurs in the final phase of cell division, known as cytokinesis, which takes place after the separation of the sister chromatids has been completed during anaphase. Thus, the condensation of chromosomes during prophase is a fundamental step that prepares them for accurate segregation in the later stages of cell division.