In a new study in Nature, the Al-Hashimi Lab at Duke University has discovered an important way that some DNA mutations happen. Or more accurately, they have provided evidence for something James Watson and Francis Crick predicted over 60 years ago.
It turns out that mutations are built into the very chemistry of our DNA. And thank goodness they are.
DNA mutations are the raw stuff of evolution. They can mean new traits that offer better survival under the right circumstances. If our DNA was copied precisely each time, life would have died out long ago on Earth. In fact, it probably wouldn’t have gotten very far in the first place.
Flash back to high school biology class for a moment where we learned that our genetic code is made up of four letters: A, T, C, and G. These researchers showed that a T, a base that normally pairs with an A, occasionally tweaks itself so that it can pair with a G instead. So now there can be a T-G base pair instead of a T-A base pair. (They also showed something similar with the G side of the equation.)
When cells copy their DNA, they split apart the double helix and use each strand to make a new piece of double stranded DNA. When the cell sees a G, it puts a C opposite it, a T gets an A and so on.
What happens with the T-G base pair is that one new set of DNA gets the original T-A base pair but the other strand gets a C-G base pair, the G matches up with a C. The new DNA now has a mutation where a T-A has been replaced with a C-G.