What defines fraternal twins?

• A. Twins that are genetically identical
• B. Twins that come from two eggs fertilized by two different sperm
• C. Twins that share the same placenta
• D. Twins that are born on the same date

Answer: (B)

Fraternal twins are defined as twins that come from two different eggs fertilized by two separate sperm. This means that each twin has its own unique genetic makeup and is no more genetically similar than any two siblings born at different times. Fraternal twins may or may not share the same placenta, as they can develop in separate amniotic sacs or together. The key distinction lies in their origin from separate eggs and sperm, which allows for the possibility of different physical traits and genetic characteristics.

The other options describe different aspects of twinning or sibling relationships but do not accurately capture the definition of fraternal twins. For example, identical twins arise from a single fertilized egg that splits, resulting in genetically identical individuals. Sharing the same placenta is common among identical twins but can also occur in some fraternal twin cases, thus not defining fraternal twins specifically. While being born on the same date typically applies to all twins, it is not a defining characteristic that distinguishes fraternal twins from other types.