Binary fission is a mode of asexual reproduction in organisms.
It involves the formation of two identical daughter cells from a single parent cell.
Binary fission involves duplication of the parent cell's genetic material, elongation of the nucleus and the parent cell, division of the nucleus and the division of the parent cell into two daughter cells through a constriction formed on the cell membrane.
Hence, the first step of binary fission is the duplication or replication of the parent cell's genetic material (DNA).