Most die before birth, but the remaining make cells destined to become eggs called primary oocytes. Primary oocytes begin meiosis I in the embryo, but do not complete it until ovulation to give rise to one secondary oocyte and a polar body. Secondary oocytes complete meiosis II after being fertilized by a sperm to make one haploid egg. The other products of meiosis are polar bodies. Usually only one secondary oocyte is released per 28-day cycle in an adult woman.
Meiosis creates haploid gametes that fuse to make a diploid fertilized egg.
The fertilized egg divides trillions of times by mitosis to make the baby. The cells in a human being continue to divide by mitosis to grow and replace cells. B. Asexual Reproduction 1. Figure 10.8 2. Single-celled Eukaryotes 3.