Twins are still different in their genes

Although identical cast-like twins are thought to share all the DNA, they will undergo hundreds of genetic changes in the early stages of development, which may lead to significant differences later, according to a new study.

Research presented at the conference of the American Association of Genetics last week can explain part of the reason why one of the couple's twins has cancer while the other is still healthy. . The study also revealed that such genetic changes, surprisingly, are quite common.

"That phenomenon is not as rare as we have guessed," said Rui Li, a pathologist at McGill University (USA) and a research author.

Although previous studies have focused on genetic changes or mutations in sperm and eggs (which can be inherited for progeny), there are not many studies that consider physical changes. . These mutations, also known as transcription errors, can occur early in the fetal development stage, but because they are not in the fetal sex cells (X or Y chromosomes), not genetic.

Other studies have also found that chemical changes or epigenetic effects can alter the type of gene that is expressed outward over time - a factor that makes twins not completely identical. A recent study has shown that twins may experience different genetic variations but this work does not determine how often this phenomenon is.

To learn about the frequency of such genetic variations in the early stages of development, researcher Li and colleagues examined the genomes of 92 identical twins such as casting and searching for differences. special pairs of base form DNA. For example, a person in the twins can carry the A gene at some point, while the other has the C gene. The team has only been able to detect the differences that occurred at the early stages of fetal development and later appear in most cells in the body.

The researchers then calculated how often these variations are. Only two of the pair of studied twins had such variations, which means that changes in DNA occur at a rate of 1 in 10 million - 10 billion base pairs copied 1 cell each time. share. Because cells in the body divide thousands of billions of times, on average, a pair of twins may contain 359 genetic differences that occur during the first stage of development.

According to Live Science, a limitation of the new study is that the authors can only estimate the rate of variation based on blood cells, while some other cells in the body divide more frequently and therefore can lead to more sudden heat. Researcher Li also admitted: "Our DNA samples were taken from blood cell samples. We need to determine the rate of mutation in other cells as well."