Quantum Tunneling [Maybe] Makes DNA More Unstable

Quantum Tunneling Makes DNA More Unstable

by Lars Fischer, Gary Stix on September 1, 2022

Researchers led by Louie Slocombe of the University of Surrey in England focused on the molecular “bases” that make up the rungs linking DNA's double strands and the hydrogen bond, formed with a proton, that holds the two sides of these rungs together. Their theoretical model incorporated the quantum effects that allow a proton, bound to the base cytosine on one strand, to spontaneously “tunnel” and hook up to the guanine base on the other.

Such an altered base pair, known as a tautomer, can quickly jump back to its original arrangement. But if the proton does not make it back by the time the two DNA strands separate—the first step of DNA replication—the cytosine might bind to a different base, adenine, rather than guanine. This unnatural pairing creates a mutation.

The researchers' model reported in Communications Physics, however, suggests that the quantum process happens so often that at any given time hundreds of thousands of tautomers may be present in a cell's genome. So even if these structures are fleeting, so many pop into place so frequently that they become a potentially rich source of mutations. This model suggests that quantum-mechanical instability “may well play a far more important role in DNA mutation than has hitherto been suggested,” the authors write. The team wonders how specific repair mechanisms deal with such quantum errors, given that the predicted number of tautomers is thousands of times greater than the total number of mutations in each human generation.