One thing which you need to understand is that it is not a set rule that identical twins are supposed to be a carbon copy at a DNA level as well. While talking about on an average level, it is stated that the identical twins tend to differ from each other by a good 5.2 genetic changes, and this has been officially reported by the Nature Genetics on January 7. This find holds great importance and the reason behind this is that identical twins, who are also known as monozygotic twins resulting from them coming from one fertilized egg, are often times under study for determining that whether or not the particular diseases, traits or the conditions result from the environmental influences or the genetic influences.
It will not be wrong to say that the identical twins were previously considered to be genetically the same, therefore whatever differences they had in health were also taken to be as a mere product of the environment and nothing else. But, with this new finding coming out in the world, it has suggested that the various genetic changes which are present amongst the identical twins are also account for the respective differences they have between each other.
The researchers who were working in Iceland succeeded in deciphering thee complete genetic makeup, of a good 381 pairs of identical twins also known as the monozygotic twins. Out of those 381 pairs, 38 were the exact genetic duplicates of one another, but majority of the identical twins had some differences in their DNAs which arose at quite an early stage in the development, this probably took place maybe right after the split or just before the one respective embryo made the split to form two. On the other hand, there were some twins who had not less but many differences on a genetic level, this also including 39 such pairs who had more than a good 100 changes between them.