What happens during the metaphase stage of mitosis?

During the metaphase stage of mitosis, chromosomes are aligned at the cell's equator, also known as the metaphase plate. This alignment is crucial for ensuring that, when the chromosomes are separated in the next phase (anaphase), each daughter cell receives an identical set of chromosomes. The alignment is facilitated by spindle fibers, which connect to the centromeres of the chromosomes and help precisely organize them along the equator of the cell. This ensures proper distribution during cell division.

The other options represent different stages or events within the cell cycle. For instance, chromosome replication occurs during the S phase of interphase, not during mitosis. The formation of the nuclear envelope happens during telophase, after the chromosomes have been separated. Lastly, chromatids being pulled to opposite poles occurs during anaphase, following metaphase. Thus, the correct understanding of what occurs in metaphase is essential for grasping how cell division maintains genetic continuity.