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How are fraternal and identical twins different?
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.
Can fraternal twins be the same gender?
Because fraternal twins originate from separate conceptions, they can be boys, girls, or one of each. Chromosomes from the father's sperm determine gender: XX for a girl and XY for a boy. … (Monozygotic—identical—twins, on the other hand, are always the same gender, either two girls or two boys.)
Are identical or fraternal twins more common?
Fraternal twins Because they come from different eggs and sperm, they only share about 50 percent of their chromosomes like any other siblings. This means they can be the same or different sexes and aren't identical.