What is the Difference Between Monozygotic and Dizygotic Twins?
The difference between monozygotic and dizygotic twins comes down to whether they have the same DNA. Monozygotic twins, otherwise known as identical twins, originated from the same fertilized ovum, and therefore the same sperm. Only about a quarter of twins are identical. The more common dizygotic twins began as two eggs separately fertilized by two sperm, and therefore they do not share the exact same DNA. Dizygotic means “two eggs,” because the twins develop side by side in the womb, but are only as similar as siblings or half-siblings. For some reason, the woman ovulates two eggs in a short period of time. The two eggs are then fertilized by two different sperm. Conceivably, these sperm can belong to separate people. Then the eggs implant themselves in the uterus, either on either side, or beside each other. When the eggs get implanted very close, and their protective amniotic membranes are touching or fused, they can sometimes resemble identical twins in an ultrasound. Usually, diz
