Twins that are neither identical nor fraternal twins
For the first time in the history of medicine a team of Physicians discovered an extremely rare Form of human twins during the pregnancy. These are neither identical nor fraternal, but semi-identical. Worldwide, only another twin pair is of this type known. What makes the twins so special, explain to the medical team that supervised the mother and the twins.
Semi-identical twins occur when two sperm fertilize the same egg. Usually, this means that the ovum developed. However, in this extremely rare case, survived the semi-identical twins, and are now four years old. This medical Sensation has been recently described in the “New England Journal of Medicine”.
What makes the case so special
The case of the Brisbane, Australia, attracted worldwide attention. For the first time physicians were able to trace how two embryos from three genes develop. In the case of a normal birth, the Embryo divides, the genetic material of mother and father in equal Parts. In the case of monozygotic twins, the Embryo splits after fertilization into two completely identical pieces. If fraternal twins occur when the mother of two ova, which were fertilized by different sperm.
Twins out of three genes
With these distinctive features, the nature can handle. Two sperm fertilize but at the same time, an ovum, it comes to a special case. It is the genetic material of the father is now two times before and once the genetic material of the mother. “Three sets of chromosomes are usually not life-compatible, and embryos usually survive nicht“, Dr Michael Gabbett explained in a message. As a clinical geneticist and coordinator of diagnostic genomics at the Institute of Health and Biomedical Innovation, he investigated the exceptional case.
Astonished Medical Team
“The ultrasound of the mother showed after six weeks, only one placenta,” says Gabbett. First, the Doctors suspected that there are identical twins. In the 14. Pregnancy week turned out, however, that one of the twins is female and the other is a male. In the case of identical twins, however, this is not possible.
The same genotype of the mother separate from the father
Therefore, it has been investigated in the womb, the DNA of the twins. The physician noted that the embryos have divided to 100 percent of the genetic material of the mother. From the paternal side and the siblings were, however, different genetic information. Thus, the semi-identical twins form a third and extremely rare type of twin formation.
For the first time in the United States
For the first time this type of twins in the United States was discovered in the year 2007. You many in infancy on, because one of the twins had no clear gender. According to a genetic study came out that the DNA of the twins was on the maternal side the same, only about half of the fathers share but of DNA.
Only two semi-identical pairs of twins in the world known
Since this case has now been two times known, asked the medical team whether there are more such semi-identical twins. They analyzed a database with genetic data from 968 twins and their parents, but could discover no other case. Thus, the semi-identical twins and from the United States, the world’s only known pairs of twins. (vb)