DNA is DNA is DNA, Right?

At one point in time in my graduate studies, I stopped being surprised at weird biological discoveries because, as one of my college professors said, when it comes to science, "there's an exception to every rule, including this one" (think about it for a minute).

But this discovery by Morris Schweitzer and colleagues at McGill University and Montreal's Jewish General Hospital revealed something that is mind boggling: your DNA may not be the same in different cells in your body:

Research by a group of Montreal scientists calls into question one of the most basic assumptions of human genetics: that when it comes to DNA, every cell in the body is essentially identical to every other cell.

Except for cancer, samples of diseased tissue are difficult or even impossible to take from living patients. Thus, the vast majority of genetic samples used in large-scale studies come in the form of blood. However, if it turns out that blood and tissue cells do not match genetically, these ambitious and expensive genome-wide association studies may prove to have been essentially flawed from the outset.

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