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Polar body twins
Who else here has heard of polar-body twins, which share about 75% of their DNA and are formed when an unfertilized ovum splits into two equal parts and subsequently is fertilized by two separate sperm.
Does anyone know how common they occur?
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About says the proportion is not known.
POLAR BODY TWINS (HALF-IDENTICAL)
Polar body twinning is very unusual and very rare. The process is quite complicated. The polar body appears when the egg has been developing, even before fertilization. It is a small cell that does not function and will usually degenerate and die. It is thought that in some cases, when the egg is old, the splitting off of the polar body takes place in an abnormal way. It then becomes larger, receives more nourishment, and does not die as it usually does. Instead, it acts as a second egg. The polar body and the egg share identical genes from the mother, but they may then be fertilized by two separate sperm from the father. This will result 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 thus are so-called half-identical twins.
Polar body twinning is very unusual and very rare. The process is quite complicated. The polar body appears when the egg has been developing, even before fertilization. It is a small cell that does not function and will usually degenerate and die. It is thought that in some cases, when the egg is old, the splitting off of the polar body takes place in an abnormal way. It then becomes larger, receives more nourishment, and does not die as it usually does. Instead, it acts as a second egg. The polar body and the egg share identical genes from the mother, but they may then be fertilized by two separate sperm from the father. This will result 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 thus are so-called half-identical twins.
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