Mitosis results in identical cells that have the same number of chromosomes as the original cell. When the process starts, the genetic material is duplicated into two chromotids. When the cell divides, one of each set of each chromotids goes to each of the daughter cells. Since the daughter cells have all the genetic material of the original, they cannot be used for sexual reproduction. When sexual reproduction occurs, the genetic material of two cells is combined. If this would happen with cells with the normal complement of chromosomes (the diploid number), the cells would have twice as much genetic material as necessary in the next generation, four times as much in the next, eight times the next, and so on. In order to keep the same number through the generations, the amount of genetic material in sperm and egg cells must be divided in half through meiosis. Then, when the egg is fertilized by the sperm cell, the diploid number is restored.