Fertilization is the process by which male and female gametes, sperm and egg, fuse together forming a zygote. The main results of fertilization are: 1. Restoration of the diploid number of chromosomes in the zygote. The zygote contains 23 chromosomes from the sperm and 23 chromosomes from the egg, restoring the normal human diploid number of 46 chromosomes. 2. Determination of the sex of the new individual. An X-carrying sperm produces a female (XX) embryo while a Y-carrying sperm produces a male (XY) embryo. 3. Initiation of cell division called cleavage. Without fertilization, the egg would degenerate within 24 hours of ovulation