Dutch scientists may have solved mystery of why some twins are identical

Discovery of DNA modifications raises hope of treatment for disorders that particularly afflict twins The medical mystery of what causes some twins to be born identical may have been solved by scientists in the Netherlands, raising hopes for treatment of congenital disorders that disproportionately afflict them. Identical twins form after a fertilised egg, called a zygote, splits into two embryos sharing exactly the same genes. The reason for the split is unknown.