The finding may be great importance for research in hereditary diseases and for the development of new diagnostic methods. "Even though the genome is virtually identical in identical twins, our results show that there in fact are tiny differences and that they are relatively common. This could have a major impact on our understanding of genetically determined disorders," said Jan Dumanksi, who co-directed the international study with his colleague Carl Bruder.
"By uncovering these small genetic differences in identical twins where one of them is sick, we have a way of tying specific genetic changes to the genesis of common diseases," said Bruder.
In the study, the research team studied 19 pairs of identical twins and found that they indeed had the same DNA but nevertheless evinced differences in the number of copies of individual DNA segments.
A segment might be missing, or more copies might exist in one twin. This could explain how one identical twin can be afflicted with a disorder while the other twin remains fully healthy, according to the scientists.
The study is published in the journal American Journal of Human Genetics.