Index – science – Where do twin sisters go in the womb?

Australian Murdoch Children’s Research Institute deals with “disappearance syndrome”, in which one of the twins dies in early pregnancy. BBC. The remnants of the twin may remain in the womb or the tissue may disintegrate and the cells are absorbed by the other twin or the placenta. The rate of twins among live births is only 1.3 percent, but according to a study, 12 percent of normal pregnancies begin as a twin pregnancy, with only the twin disappearing in every eighth pregnancy.

Recent research on missing twins uses a new method to find out if someone has a twin sister in the womb. The accuracy of the method is about 60 to 80 percent.

Why would there be twins?

Identical twins are born when an egg fertilized by a sperm accidentally ruptures early. Identical twins only occur in humans, dogs, cattle, horses, and pigs. Their existence is evolutionarily poorly understood, because the offspring of genetic diversity gives them a better chance of survival.

The researchers originally wanted to investigate the role of so-called epigenetic processes — the chemical markers of genes — in the development of twins. These epigenetic marks can be added to genes or removed from the human body in response to changes in a person’s environment or lifestyle. It has been shown that epigenetic changes are essential for early embryonic development.

In particular, DNA methylation, in which a small chemical label is added to DNA called a ‘methyl group’, helps to regulate embryonic gene function, thus enabling healthy development.

To find out whether DNA methylation plays a role in the development of twins, the research team analyzed the level of DNA methylation in 924 samples of identical twins in the United Kingdom, Australia, the Netherlands and Finland. This sample was compared to a control group of 1033 non-identical twins.

genetic signature

The researchers found a distinct pattern of methylation in samples of identical twins, also referred to as a ‘molecular signature’ or ‘epigenetic signature’. When samples were taken from different people at different times, it was discovered that this sample remained stable.

The discovery of this distinct, stable signature showed that identical twins retain the epigenetic signature throughout their lives, so it can be ascertained whether a person was originally an identical twin, even if their brother was never born.

The test is only applicable to identical twins. Non-identical twins are born when a woman produces two eggs and is fertilized by another sperm. This mainly occurs in older mothers or in families where identical twins are common. Race can also affect twin pregnancies: non-identical twins have the highest chances among Nigerians, 40.2 per 1,000 births, and lowest among Japanese.

This is a great hack for several reasons. Helps identify identical twin survivors whose siblings died before birth.

says Nancy L. Segal, MD, professor of psychology who specializes in twin studies at California State University at Fullerton, about the new procedure.

phantommaker

There are many hypotheses as to why the twins disappeared.

There may be something wrong with one of the fetuses, or the mother may not have enough space. The uterus was eventually made for an infant, and it might just be a correction to ensure the health of the surviving twin.

The rare condition is called “fetus-in-fetus” or “parasitic”, in which one twin is absorbed into the other and the parts remain in the other.

In the case of non-identical twins, some of the genetic material of the deceased twin may enter the surviving twin. In 2015, the Washington man’s case was in dust: When his son was born, only 25 percent of his DNA was identical. It turns out that the father had a twin brother who died in the womb, but the man’s DNA absorbed some of his twin cells. He has now lived in his son.

(Cover photo: Brianna Vondrac (m) and Arina Vondrac of Bedford, Cleveland, both sitting in their buggy at the 31st Twins Fest on August 5, 2006 in Twinsburg, Ohio. Photo: J.D. Poli/Getty Images)