DNA is known to mutate regularly, for better or worse, driving both evolution and disease. Researchers at the University of Surrey have now found evidence that some of these spontaneous mutations could be caused by the spooky realm of quantum mechanics.
DNA gets its famous double helix shape from molecules called bases that pair up through hydrogen bonds. These bases, denoted by the letters A,C, T and G, usually follow strict rules about how they link up – A bonds to T and C bonds to G. But sometimes these hydrogen bonds can be changed, meaning the bases can pair up with the wrong partner. This produces point mutations in the DNA, which are mostly harmless but can sometimes lead to genetic disorders.
In the new study, the Surrey researchers discovered that some of these modifications can occur as a result of a strange quantum physics phenomenon known as quantum tunneling. It sounds like science fiction to us living in the world of classical physics, but sometimes particles can spontaneously tunnel through barriers that they shouldn’t have enough energy to overcome.
Think of it like a ball sitting in a valley. Classical physics says that to get that ball to the other side of the hill requires a certain amount of energy to push it up and over the hill. But quantum physics can allow that ball (i.e. a particle) to suddenly “tunnel” through the hill of its own accord and appear on the other side, almost instantaneously. Again it sounds unbelievable, but quantum tunneling is a well-documented phenomenon that occurs in a range of scenarios, such as nuclear fusion.
In the case of DNA mutations, the team says that the particles doing the tunneling are protons within the hydrogen atoms, which can jump from one side of the bond to the other. If they happen to do this just before the two DNA strands are cleaved as part of the cell replication process, the protons can become trapped on the wrong side, leading to a DNA mismatch and a potential mutation.
The idea that this could happen in DNA mutation was first suggested decades ago, but the mechanism has largely been overlooked since. That’s because the biological environment has long been presumed to be too warm and complex for quantum tunneling to occur.
But in the new study, the researchers found that not only does it happen in this environment, but the warmth actually activates the protons to make the jump. The team used a process called open quantum systems to model the dynamics of the process, and showed that these protons are jumping back and forth more often than previously thought. This suggests that proton transfer from quantum tunneling plays a more important role in genetic mutations than it’s usually given credit for.
“Biologists would typically expect tunneling to play a significant role only at low temperatures and in relatively simple systems,” said Dr. Marco Sacchi, co-corresponding author of the study. “Therefore, they tended to discount quantum effects in DNA. With our study, we believe we have proved that these assumptions do not hold.”
The team says that if the model holds true, it could have a wide-ranging impact on current models of genetic mutations.
The research was published in the journal Nature Communications Physics.
Source: University of Surrey
