Tunneling, a well-known quantum effect, predicts mutations in DNA, and is likely much more prevalent than previously thought.

Our cells are constantly duplicating. In each duplication, a copy of the genetic material is made, the DNA that contains the recipe to make the being we are, and mutations sometimes occur in the process. Normally, our immune system detects these mutated cells as defective or foreign and destroys them. When the cleaning process fails, it can lead to cancer.

But what produces these mutations, these duplication failures? Radiation, which destabilizes the atoms that make up DNA, is known to be an important factor, but it is not the only one. A theoretical analysis of the links within DNA suggests that quantum effects may produce mutations much more often than previously thought, according to what was published in a University of Surrey studyIn the United Kingdom.

The researchers started with a quantum model of the cytosine-guanine base pair, two of the four present in DNA. Until now, most experts assumed that quantum effects played a negligible role in the cell. However, in this study it was seen that the tunnel effect makes it much more likely that an alternative form of this base pair, known as a tautomer, will appear with altered bonds.

Under certain circumstances, a tautomeric base pair alters the genetic sequence at this point, so the quantum effect makes mutations more frequent. The result could have far-reaching consequences for explaining genetic mutations.

The tunnel effect and tautomers

Tunneling is one of the most well-known effects of quantum mechanics. It occurs when a particle violates the principles of classical mechanics and crosses a potential barrier greater than its kinetic energy. It is as if a person capable of jumping a meter fence runs to a 5 meter fence, jumps and appears on the other side.

This effect, impossible in the macroscopic world, is common in the world of subatomic particles, to the point of being used for years in the semiconductors that all our electronic devices contain.

In the case of DNA mutations, tautomeric forms appear when hydrogen bonding protons move toward the opposite bonding partner. DNA is very sensitive to the position of protons when duplicated. If a base pair tautomer has been formed, cytosine does not bind to a new guanine, but to adenine, due to the rearranged bonds. Therefore, a mutation occurs in the new strand of DNA.

The fact that tunneling could give rise to tautomeric base pairs had also been theoretically described. However, due to the very short duration of these quantum states, quantum effects were previously considered unlikely to be relevant to biology, and it was assumed that tautomers would return to normal form too quickly to survive the replication timescales of the universe. DNA.

However, the researchers maintain that it is precisely the speed of quantum processes that makes the formation of tautomers relevant. The quantum mechanical process is so fast that a thermal equilibrium is reached in which about one in 5,000 base pairs is a tautomer. This figure is well above the average mutation rate of the human genome, where about 25 new mutations per billion base pairs occur in each generation.

On the other hand, there is the possibility that there are specific repair mechanisms for this type of errors, which have not yet been discovered. Another question is whether these mutations due to quantum effects can have evolutionary advantages, for example because a higher mutation rate facilitates adaptations, or is it simply an accident of evolution.

REFERENCE

An open quantum systems approach to proton tunneling in DNA

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