They duplicate during Interphase (more specifically During S phase)! :)
General short answer for remembering Mitosis:
Prophase=chromosomes condense and attach.
Metaphase=chromosome Align at opposite ends of the cell.
Anaphase= chromosomes are are being split apart.
Telophase= chromosome relax are are fully separated. :)
I hope all this information I wrote will help you in some way! Good luck! ☺️
