When do chromosomes line up during cell division?

During cell division, chromosomes line up during metaphase. This stage is characterized by the alignment of chromosomes along the metaphase plate, which is an imaginary plane equidistant from the two spindle poles. The proper alignment is crucial for ensuring that each daughter cell receives an identical set of chromosomes when the cell divides.

The metaphase stage follows prophase, where chromosomes condense and the mitotic spindle begins to form, but it is during metaphase that they align in preparation for separation. This organization ensures that during anaphase, when the sister chromatids are pulled apart towards opposite poles of the cell, the resultant division is equal and organized. Telophase, on the other hand, is the phase where the divided chromosomes at each pole begin to de-condense back into chromatin and the nuclear envelope re-forms around each set, thus concluding the separation process rather than aligning the chromosomes.