Wednesday, January 9, 2013

Adaptive Mutations and Quantum Mechanics

Adaptive Mutations
A principle tenet of New-Darwinian evolutionary theory is that mutations occur randomly, after which natural selection chooses “the fittest” organism to survive and thus pass on the more adaptive genes. Yet over the past several decades a new phenomenon has been observed named adaptive or directed mutation which challenges the random nature of mutations. Cairns et al (1) placed ecoli bacteria that did not have the gene necessary to metabolize lactose into an environment with only lactose as a nutrient. The result was that mutant bacteria arose that were able to ferment lactose. Yet when the same lactose deficient bacteria were placed in a lactose-free medium, mutations for the lactose metabolizing gene arose at a much lower rate. This phenomenon was dubbed adaptive mutation because these new mutations occurred seemingly in response to the environment.
Since then adaptive mutation has been reported in many other studies using bacteria and eukaryotes (organisms containing nuclei) and is a well recognized phenomenon (2,3,4,5,6), though still controversial.

Adaptive mutations are defined thus:
1) They occur in cells that are not dividing
2) They don’t depend on rate of replication but on time
3) They appear only after the cell is selectively challenged in some way
Neo-Darwinian theory has no way of explaining this phenomenon.

Quantum Mechanics
Quantum mechanics is a field of physics so strange that even Einstein, who had a hand in developing it, didn’t believe in its implications. Yet in all the experiments conducted so far—and there have been very many—it has proven to be precisely correct.

Entanglement. Schrodinger’s equations describe the phenomena of quantum mechanics, later refined by others. One such phenomenon is that an object (electron, proton, even larger molecules) can exist in more than one place at the same time. Another is that two objects at any distance (even light years away) can be “entangled.” The classical experiment to illustrate entanglement is of two electrons with opposite spin. If one changes the spin of one electron the other changes its spin automatically, no matter the distance between the two. The theory states that the electron exists in a “potentiality wave” in which its exact state is not determined until an observation is made, at which time the wave function of all potentialities “collapses” into the one you observe. In this view, the act of observation causes the myriad potential states to be reduced to one. We therefore have mathematical virtual states and an actual physical one.

Alternate Quantum Theory. One relatively recent interpretation of this phenomenon is that there is no collapsing of potential states but that all states exist in universes that form part of a multiverse. In this view, the electron, and every other object in this universe (including ourselves), exists in every possible configuration in all the other universes.

Mutations. Watson and Crick, as well as Schrodinger and many others, have proposed that mutations are initiated by “tautomerization” of single protons. According to quantum mechanics, protons in DNA are not localized to certain positions but exist in many quantum states along the double helix of DNA which correspond to different codes. Just as in the electron experiment, DNA drops out of the quantum potential world when it interacts through entanglement with the actual physical environment. The entire DNA molecule can thus be seen to be in a quantum state. The lactose deficient bacteria is thus considered to have its DNA exist in a quantum wave in which all mutations are possible. It collapses out of its quantum state when the environment is changed (only lactose as a nutrient) to produce the appropriate mutation out of all the possible mutations it was capable of in its quantum wave form. When no lactose is present the environment is not changed and thus the entanglement will not cause the DNA to respond. The DNA will thus remain in the quantum state of potential mutations until the system is stressed in some other way. This view tries to explain why the rate of mutations was much lower in lactose deficient bacteria that were placed in a medium with no lactose. DNA is thus seen as being entangled with its environment and able to respond when the environment is changed (i.e. the presence of lactose).

Inverse Quantum Zeno Effect. A further explanation is given. In a phenomenon called the inverse quantum Zeno effect (7), a series of measurements along a particular path has been shown to force the quantum system to evolve along that path. In the same way, the environment (the presence of lactose) is seen to cause mutations to occur in a quantum system (DNA) along the path of specific mutations (out of all the possible mutations) which will allow the cell to metabolize lactose.

So how does it all work? If the world does exist in a quantum universe, which all evidence says it does, then the biological sciences will need to incorporate quantum mechanics in their understanding of how cells and organisms actually work. Even more importantly, a broader theory will be needed to explain how evolution works to produce such a diversity and complexity of organisms in such a relatively short time. Quantum mechanics may shed some light on the rapid evolution of not only the genetic but the epigenetic (regulatory) systems which a growing number of scientists are unable to explain with a Neo-Darwinian theory.

1) Cairns et al 1988. The origin of mutants. Nature 335, 142-145.
2) Hall, B.G., 1990. Spontaneous point mutations that occur more often when advantageous than when neutral. Genetics 126, 4-16.
3) Hall, BG., 1991. Adaptive evolution that requires multiple spontaneous mutations: mutations involving base substitutions. Proc. Natl. Acad. Sci. USA 88, 5882-5886
4) Hall, B.G., 1997. Spontaneous point mutations that occur more often when advantageous than when neutral. Genetics 126, 5-16
5) Foster, P.L., Cairns, J., 1992. Mechanisms of directed mutation. Genetics 131, 783-789.
6) Wilke, C.M., Adams, J., 1992. Fitness effects of Ty transposition in Saccharomyces cerevisiae. Genetics 131, 31-42
7) Aharonov, Y., Vardi, M., 1980 Meaning of an individual ‘Feynman path.’ Phys. Rev. D 21, 2235-2240.