What are polar body or “half-identical” twins?
Polar body twins are believed to occur when the mother’s egg splits before fertilization and one half (referred to as the ‘polar body’) is also fertilized by a different sperm. This results in twins who share half their genes in common (from the mother) and the other half different (from the two sperm). They share some features of identical twins and some features of fraternal twins and are so-called half-identical twins. However, DNA-based zygosity tests are currently not available to determine if twins are polar-body twins.
Polar body twins are believed to occur when the mother’s egg splits in the normal course of ovulation and one half (referred to as the ‘polar body’) is also fertilized by a different sperm. In theory, this results in twins who share half their genes in common (from the mother) and the other half different (from the two sperm). They share some features of identical twins and some features of fraternal twins and are so-called half-identical twins. However, there are intervening genetic recombinations during ovum development which may make polar bodies different from each other and therefore not possessing the same maternal DNA.
