Fraternal twins: Learn the key differences and

Learn the key differences and similarities between fraternal and identical twins, such as genetic code, gender, blood type, appearance, and risks. Find out how to identify and test for zygosity, and how environmental factors can affect twin phenotypes. Identical vs fraternal twins: what are the main differences between the two types of twins? Yes, there are other subtypes of twins. But, in most cases, a woman either gives birth to a fraternal twin or an identical one. The number of identical twins born is comparatively less, while fraternal twins are more common. Because fraternal, or dizygotic, twins are 2 separate fertilized eggs, they usually develop 2 separate amniotic sacs, placentas, and supporting structures. Identical, or monozygotic, twins may or may not share the same amniotic sac, depending on how early the single fertilized egg divides into 2. Fraternal twins (also called dizygotic twins) result from the fertilization of two separate eggs with two different sperm during the same pregnancy. Fraternal twins may not have the same sex or appearance. They share half their genomes, just like any other siblings.