Genetic mutations are changes in the DNA of an organism that can result from errors made during cell division, viral infections or exposure to radiation and carcinogens. They are essential to evolution as they can lead to adaptations that allow certain organisms to outcompete others in their environment but can also lead to disease.
They can be thought of as ‘spelling mistakes’ in an organism’s genetic code. DNA is made up of four bases – A, C, T and G – that under normal conditions always bond together in specific ways: A always bonds to T, for example. These bonds form the ‘rungs’ of the twisted ladder that makes up DNA’s iconic double helix structure.
However, if the nature of these bonds becomes altered in some way the normal pairing rules breakdown, leading to incorrect bases becoming attached to one another and possibly giving rise to a mutation.
Now, researchers from Surrey University have found that this mismatched bonding may be caused by a mysterious phenomenon known as quantum tunnelling.
Tunnelling occurs when particles move through a barrier that, according to classical physics, they shouldn’t be able to via quantum effects. The barrier may be a physically impassable medium, such as an insulator, or a region of high energy that the particle isn’t energetic enough to overcome.
In the case of genetic mutations, the Surrey team found that protons, subatomic particles involved in the bonding of DNA, are continuously tunnelling back and forth across the energy barrier found between the two sides of the helix.
If they do this in the moments before the helix splits along its centre during the first stage of the DNA copying process, some of the protons can get caught on the wrong side. This can lead to an error in copying and, potentially, a mutation.
“Biologists would typically expect tunnelling to play a significant role only at low temperatures and in relatively simple systems,” said the study’s co-author Dr Marco Sacchi. “Therefore, they tended to discount quantum effects in DNA. With our study, we believe we have proved that these assumptions do not hold.”
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