Evolution: Just a Theory

And like most theories, evolution evolves, growing and changing as new discoveries demand. We may be about to experience a little punctuated equilibrium in the theory, not to mention a revision of the genetics textbooks (sorry, Gregor Mendel, but hey, you've had a great run, and given what you had to work with, you did a damn fine job), if the findings reported in this article from Nature appear to hold for other species.

The summary version: the authors have found a plant that can undo mutation in the next generation, i.e., even though both parents carried the mutated DNA, the new plant seems to have reverted to the unmutated gene. The way we were all taught genetics, this shouldn't be possible.

[Weak in your recollection of genetics? Okay, the DNA works like a row of pegs of four different shapes, arranged in a long row. (Actually, a double helix, but don't worry about that right now.) The RNA comes along and matches up holes with pegs to form sort of a mold from which is made a new exact copy of the DNA. Any errors--mutations--in the DNA get copied to the RNA and thereby into the offspring DNA. A child only gets DNA from its parents, So if both parents have mutated DNA, there's no "correct" original to make the child's DNA, so the mutation will have to be passed on to their offspring. Want to know more? Go here.]

The authors guess that, since there's nothing resembling a good copy of the part of the DNA in question in these plants, the plant has to have a backup somewhere else, possible in some other RNA, stored for emergency use. They speculate (all this remains to be tested) that the emergency backup is triggered by some sort of environmental stress. (Smart programming, huh?)

But this will be very important if it turns out to happen in species other than this particular plant. Like, oh, say, perhaps humans. The practical applications are obvious:

A similar process might even go on in humans. This is suggested by rare cases of children who inherit disease-causing mutations but show only mild symptoms, perhaps because some of their cells have reverted to a normal and healthier genetic code.

If humans do correct their genes in this way, Pruitt [the lead author] suggests that the procedure might be usefully hijacked by researchers or doctors. They might be able to identify the RNA molecules that carry out the repair and use them to correct harmful mutations in patients.

Of course all this is still itself just a relatively limited amount of information. The authors could be wrong. Or this plant could behave differently than anything else on earth. But if it is in fact the first indication of a new theory of how mutations operate, it will call for a revision in our thinking with regard to evolution: if there are indeed backup copies of unmutated DNA, how do the mutations that account for evolution survive over time? How does the trigger function so not to revert to unmutated backup? What triggers (or doesn't trigger) the trigger?

It will be years of research before these questions are answered. But once they are, when you think back to what we used to believe about how evolution and genetics functioned, remember where you were when you read this, and tell those young'uns that you remember the day the paradigm started to shift.