(ORDO NEWS) — Mistakes happen. Especially when it comes to replicating huge sequences of DNA inside our cells. And this is good. If it were not for the errors in our genes, which we call mutations, natural selection would not be possible and life would freeze in the water.
As important as mutations are to everything from disease to biodiversity, we know very little about the physics of this process.
Results from the University of Surrey in the UK have revived the notion that the underlying mechanism behind chemical sleight of hand, which spontaneously changes from one coded base to another, is quantum in nature.
In particular, a significant part of the mutation process is the displacement of one hydrogen, which sticks together the genetic bases, forming the “rungs” of the twisted ladder structure of DNA.
This occurs as a result of the process of tunneling, breaking the bonds between the genetic bases of guanine and cytosine in time to make irreversible changes.
Quantum tunneling is a natural consequence of the uncertainty of particle characteristics under limited conditions.
If a subatomic object, such as a proton, is brought closer, its position becomes more and more uncertain.
Objects of this magnitude could theoretically exist outside of the limited barrier, slicing their way through walls as easily as a ghost would slither through a haunted house.
While this is a fundamental feature of reality at the quantum level, the way a particle’s properties get entangled with other particles jostling in a warm, noisy environment prevents it from easily scaling into the macroverse.
So we thought for a long time.
“Biologists have generally expected tunneling to play a significant role only at low temperatures and in relatively simple systems,” says chemist Marco Sacchi.
“Therefore, they tend to ignore quantum effects in DNA. In our study, we believe we have proven that these assumptions are wrong.”
The team’s theoretical modeling of the change in bonds between guanine and cytosine bases casts doubt on several assumptions related to the chemistry of this common form of mutation.
Since the early days of studying the structure and chemistry of DNA, scientists have believed that the main cause of mutation is the movement of hydrogens that bind bases on opposite strands of DNA.
This movement can turn the base into a tautomer – a new molecule with the same shape as before, but with a subtle, different configuration of elements.
Hydrogens are supposed to jump over the boundary between the filaments in a process called double proton transfer, and this action is remarkably similar to quantum tunneling.
However, aside from the assumption that biological systems are too hot and stressful for such a quantum event to occur, any double proton transfer that occurs in this manner must be eliminated by the cell’s editing enzymes.
By looking more closely at the physics of the process, the researchers demonstrated that under the temperature conditions of a typical cell, quantum effects should cause protons to move back and forth at high speed, causing the bases to spread out into tautomers.
Since the residence time of the tautomer in this state is fleeting, the replication mechanism that copies the DNA strand is unlikely to recognize its presence.
However, if this process leads to some kind of imbalance between the bases, causing the ratio between the base and its tautomer to change in some way, then it is quite possible that this shift can be recorded as a mutation.
Moreover, from a mathematical point of view, the presence of these ghostly tautomeric versions of each base is large enough that this particular category of mutations is much more common than we think.
Future experiments will be needed to confirm the predictions made in the study, especially with regard to things like proton hopping speeds at different temperatures.
It also remains to be seen whether quantum effects play a role in other base pair changes or even other kinds of mutations.
Biologists are gradually realizing the role of quantum uncertainty in a number of biochemical processes.
It is becoming increasingly clear that the boundaries of the quantum universe are not as solid as we might imagine.
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