Why is it necessary for DNA to replicate as the first step in mitosis?

DNA is a macromolecule composed of nucleotides which carry the genetic instructions used in the growth, development, functioning and reproduction of the cell. One of the most important characteristics of DNA is its ability to make several copies of it (to be copied via the process of replication). When the cell divides into two it must carry each copy of DNA into the divided cells. Through replication, the DNA transfers the information necessary for creating an exact copy of it in the new daughter cell. The transfer of the DNA to the next generation of cells is essential for the function of the whole organism.

DNA replication will make the organism to reproduce the genetic code and transfer it to the next generation (through the reproduction) and thus, to continue the species.