Sex cells are gametes (sperm and eggs). 1. They are haploid, which means that they have half the number of chromosomes of somatic (not sex) cells. This way, when they combine with another sex cell (a sperm if it's an egg and vice versa), the zygote will have the correct number of chromosomes. 2. Sex cells are genetically different from their parent cells as well as the other sex cells that are produced by meiosis (which is 3 other sperm in males and usually 2-3 polar bodies in females). The reason for this is that a couple of events (namely crossing-over, independent assortment of chromosomes, and random fertilization) that happen in meiosis create genetic variation. These events do not happen in mitosis (which is the process that occurs for somatic cells).