Final answer:
Chromosomes are paired up during Metaphase I and Anaphase I of the cell cycle.
Step-by-step explanation:
The chromosomes are paired up during Metaphase I and Anaphase I of the cell cycle.
In Metaphase I, the chromosomes appear in homologous pairs on the spindle. In Anaphase I, the pairs of chromosomes are pulled apart and migrate towards the poles of the cell.