New studies discover that identical twins are not always genetically identical

The same twins may not be as identical as we thought. Icelandic researchers have discovered genetic differences that begin early in embryogenesis.

Scientists have long used the study of identical twins to study the effects of nature and nurturing. Since they share the same gene, it is accepted that such physical or behavioral differences between siblings must be due to external influences.

But that may not be the case, suggesting a new study published in the journal Thursday. Nature genetics..

Monozygotic twins come from a single fertilized egg, or zygote.

In any embryo, cell division can cause mutations, but this type of genetic difference has not previously been measured between identical twins.

In the course of four years of research Icelandic researchers so DeCode GeneticsWe found that Reykjavik’s biopharmacy company, sing or singing twins, has genetic differences that begin early in embryogenesis.

Scientists have sequenced the genomes of 387 pairs of identical twins and their parents, spouses, and children. Track the divergence of the mutation. The authors found that twins differ by an average of 5.2 early developmental mutations.

In about 15% of twin pairs, one sibling had many of these mutations that the other twin did not have.

A gene mutation is an error or change in DNA. Mutations occur when the genetic code sequence is broken or changed in some way. Most mutations are harmless, but some are serious and can lead to diseases such as cancer. Mutations can also affect physical attributes such as hair color.

This is not the first study to suggest a difference between so-called identical twins. A paper published in The American Journal of Human Genetics in 2008 revealed some genetic differences between siblings. But new research has taken a step beyond that by including the DNA of extended families.

Genetic difference

Some of the subjects of the study revealed surprising differences, the study co-author Cali Stephanson told CNN.

“We found a pair of identical twins that were found to be mutated in all cells of one body but not at all in the other twin. Then, in the body of one twin. We found twins that had mutations in all of their cells, but only 20% of the other cells, “said Stefansson, founder and CEO of DeCode Genetics, a US subsidiary. I have.Pharmaceutical company Amgen..

The significance of this is important because, according to Stephenson, the study concluded that the “role of genetic factors” in shaping the observed differences between identical twins was “underestimated.” ..

He acknowledged that both science and the wider society are fascinated by singing twins, adding that “the connection between icing twins is magical.”

But his team’s work is more about splitting than integrating them.

“Imagine you have the same twins raised apart. If one of them develops autism, the classic interpretation is that it is an environmental factor. , Our job is that you Due to the environment, twin genomes need to be sequenced to determine the cause of autism, “says Stephenson.

The “mutation differences” he told CNN can cause a variety of “catastrophic childhood illnesses,” including severe epilepsy and various metabolic disorders.

“It’s absolutely amazing that a significant proportion of such horrific syndromes in very early childhood are due to genomic mutations,” he said.

“This is an extraordinarily exciting and insightful effort to identify the early cellular mechanisms that explain the genetic differences in MZ (monozygotic) twins,” said the twins at California State University, Fullerton. Nancy Seagull, the author of the study and a professor of psychology, said. I am involved in research.

“It is well known that MZ twins do not show complete similarities, and that some dissimilarities may reflect genetic differences. This study is a study of MZ twins. We provide new information on the causes of the differences, “said Seagull, who is also the director of the CSU’s Twin Research Center.

The study “did not deny environmental factors in early and late development,” she added, but showed that “some twin models underestimate genetic effects and require modification.” ..

According to Segal, the study also questioned how the findings should be applied, including whether to intervene before birth to correct a particular genetic disorder.

“There are many intriguing questions raised by this extraordinary study,” she said.