This is a process of the splitting in two, of cells in the body or in single cell bacteria or protists to make daughter cells from the parent. Consequently the number of chromosomes during mitotic fission must remain the same. So the original genetic material must be duplicated and then separated into the daughter cell. This is done by proteins and enzymes in cell division, in the nucleus of Eukaryotic cells, during mitosis.
Artist's rendering of an animal cell.