Scientists may have solved mystery of how some twins are identical

Scientists may have gotten closer to solving a mystery in how identical twins are formed after conception.

Dutch researchers have been exploring how a fertilised egg, known as a zygote, splits into two embryos with considerably similar genes in each.

The reason why the egg splits is unknown – but the main theory has been that the time of action happens randomly.

This is unlike the time of action whereby non-identical twins develop as a consequence of two separate eggs being fertilised by two sperm – a course of action that runs in families, unlike “monozygotic twinning”, researchers said.

Now, scientists led by the Vrije Universiteit Amsterdam believe they have found a shared “identifying characteristics” on the DNA of identical twins.

Their study looked at the epigenetic changes in the twins’ DNA, which control the expression of genes but not the DNA ordern itself.

It found that identical twins from across the world shared similar chemical marks at 834 points across their genomes, which are each of their complete sets of DNA.

It is however to be proved that the chemical marks on the DNA causes a zygote to divided, but the scientists said that it is a plausible working theory.

Assistant professor Jenny von Dongen said: “We may have identified a mechanism that causes cells to divided. It’s also possible that these changes arise after the cells separate.”

The researchers hope that the finding of the shared marks could also be helpful for a wide group of people, such as those who believe they may have had a twin that “vanished” in their mother’s womb.

The scientists said the finding could help determine with up to 80 per cent accuracy whether someone is an identical twin, had been separated from their twin at birth, or unaware they had lost their twin in the womb in what is known as vanishing twin syndrome.

The syndrome develops in as many as 12 per cent of pregnancies, but just under 2 per cent of mothers end up carrying both to term – resulting in many people unaware that they had a twin.

The research has been published in the journal character Communications.

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