What happens to chromosomes during anaphase?

During anaphase, the distinct and crucial action that occurs is the separation of chromosomes, which move toward opposite poles of the cell. This process is essential for accurate cell division, ensuring that each daughter cell receives an identical set of chromosomes. Prior to anaphase, during metaphase, chromosomes are aligned in the center of the cell, but it is during anaphase that the sister chromatids are pulled apart due to the action of spindle fibers attached to the centromeres of each chromosome. This movement is vital for maintaining genetic consistency as the cell prepares to divide.

The other statements pertain to different phases or characteristics of cell division. For example, the visibility of chromosomes and the dissolution of the nuclear envelope occur during prophase, and the line-up of chromosomes occurs during metaphase, while the return to a less coiled chromatin state reflects the activity in telophase rather than anaphase. Thus, the separation and movement to opposite ends of the cell during anaphase is the defining feature of this phase in the cell cycle.