A study carried out by Swedish, Dutch and American scientists has found that identical twins are not actually completely genetically identical. The scientists studied ten pairs of identical (or monozygotic) twins, in which one twin from nine of the pairs had an hereditary disease (e.g. Parkinson’s or Dementia) and the other did not. In the past it was known that differences between twins were caused by environmental factors and epigenetic factors (which influence the expressions of a gene). This study has now shown that there are minuscule differences in the actual genetic make up of identical twins, contrary to past assumptions. This may explain the subtle differences in the phenotypes (outward appearance) of twins who come from the same embryo.
"When we started this study, people were expecting that only epigenetics would differ greatly between twins,” said Jan Dumanski, a professor of genetics at the University of Alabama at Birmingham and an author of the study. “But what we found are changes on the genetic level, the DNA sequence itself.”
It is not known yet whether this change occurs at the embryonic level of production and/or as the individual ages. This study, published in the American Journal of Human Genetics may help scientists understand and treat genetically induced diseases more fully by being able to easily identify the different gene between the two twins, consequently finding the gene/s which cause the disease. In the meantime, the common assertion that “no two people are genetically the same, except identical twins” will have to be modified, and numerous biology textbooks reprinted!
"When we started this study, people were expecting that only epigenetics would differ greatly between twins,” said Jan Dumanski, a professor of genetics at the University of Alabama at Birmingham and an author of the study. “But what we found are changes on the genetic level, the DNA sequence itself.”
It is not known yet whether this change occurs at the embryonic level of production and/or as the individual ages. This study, published in the American Journal of Human Genetics may help scientists understand and treat genetically induced diseases more fully by being able to easily identify the different gene between the two twins, consequently finding the gene/s which cause the disease. In the meantime, the common assertion that “no two people are genetically the same, except identical twins” will have to be modified, and numerous biology textbooks reprinted!
Laura Fenlon
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