It has always been believed that monozygotic twins, also called identical, were the same because they had the same genetic load and that differences in health, behavior or others were due to environmental factors.
Well, a recent study on schizophrenia has shown, indirectly, that identical twins are not genetically the same.
The study was carried out in the University of Western Ontario and the objective was to investigate pairs of twins in which only one of them suffered from schizophrenia. The reason for using twins for this study, as well as for most studies with twins, is obvious: if you have two genetically equal people, a lot of variables that could alter the outcome of a study are suddenly eliminated.
Seeing then that there were pairs of twins in which one of them had schizophrenia and the other did not decide to look for the environmental cause of the disease.
The surprise was that, instead of finding such an environmental factor, they observed that identical twins did not have the same DNA. In this way the study was invalidated in its methodology (if you no longer have two identical subjects, schizophrenia could come due to genetic reasons) and all studies conducted to date with twins were also questioned.
In addition to this, they realized that a person's DNA is not always the same, but as time passes it may change. Shiva Singh, one of the authors of the study stated the following:
The cells divide and differentiate as we develop. More important, these cells can lose or acquire additional DNA. The genome is not static.
Let's say that with this discovery there is a small earthquake in the knowledge of the human genome (that DNA is variable is an important novelty) and in studies with twins to date. We do not know what the repercussions of this new knowledge will be, but it is interesting to see that truths that were considered absolute are suddenly refuted by new research.
