In order to create a fertilized cell, the number of chromosomes in the sperm and egg must be equal. This is because during fertilization, the sperm and egg combine to form a zygote, which is the first cell of the new organism. The zygote contains the full complement of chromosomes that will determine the characteristics of the organism. If the number of chromosomes in the sperm and egg were not equal, the zygote would not be viable and the organism would not develop properly.