Fraternal Twins

Fraternal Twins

• A. Twins from a single fertilized egg that split
• B. Two eggs fertilized by same sperm
• C. Twins who develop from separate fertilized eggs
• D. Twin siblings from random mutation

Answer: (C)

Fraternal twins happen when two eggs are released and each is fertilized by a different sperm, producing two separate zygotes. This is dizygotic twinning, so the twins develop from two fertilized eggs and are genetically similar to regular siblings (about 50% of their DNA on average). They can be different sexes and often look different from each other. This differs from identical twins, which come from one egg that splits into two embryos. The idea of two eggs being fertilized by the same sperm isn’t the typical explanation for fraternal twins, and the other option about twin siblings arising from a random mutation isn’t how twinning occurs.

Fraternal twins happen when two eggs are released and each is fertilized by a different sperm, producing two separate zygotes. This is dizygotic twinning, so the twins develop from two fertilized eggs and are genetically similar to regular siblings (about 50% of their DNA on average). They can be different sexes and often look different from each other. This differs from identical twins, which come from one egg that splits into two embryos. The idea of two eggs being fertilized by the same sperm isn’t the typical explanation for fraternal twins, and the other option about twin siblings arising from a random mutation isn’t how twinning occurs.