Mitosis and cell division?

it is important that DNA replicates it self because in mitosis the DNA is aligned along the metaphase plate to be seperated to each end of the cell, if the DNA would no copy, one off mitosis could never occur because the mioitic spindils, which come from the centrioles, would not be able to attach to teh kineticore on the chromosomes. Even if they could it might result in haploid cells, which is not the point of mitosis