Updating the theory of mutation

There has been some evidence to suggest that free radicals and some reactive nitrogen species trigger and increase cell death mechanisms within the body such as apoptosis and in extreme cases necrosis.

In its current form, this theory proposes that reactive oxygen species that are produced in the mitochondria, causes damage to certain macromolecules including lipids, proteins and most importantly mitochondrial DNA.

An alternative vision of evolution is beginning to crystallize, in which the processes by which organisms grow and develop are recognized as causes of evolution.

Some of us first met to discuss these advances six years ago.

For most biological structures, free radical damage is closely associated with oxidative damage.

Antioxidants are reducing agents, and limit oxidative damage to biological structures by passivating them from free radicals.

We believe that the EES will shed new light on how evolution works.

We hold that organisms are constructed in development, not simply ‘programmed’ to develop by genes.

Damage occurs when the free radical encounters another molecule and seeks to find another electron to pair its unpaired electron.Two sources inspired Harman: 1) the rate of living theory, which holds that lifespan is an inverse function of metabolic rate which in turn is proportional to oxygen consumption, and 2) Rebbeca Gershman's observation that hyperbaric oxygen toxicity and radiation toxicity could be explained by the same underlying phenomenon: oxygen free radicals.Noting that radiation causes "mutation, cancer and aging", Harman argued that oxygen free radicals produced during normal respiration would cause cumulative damage which would eventually lead to organismal loss of functionality, and ultimately death.We apply the model to a dozen real protein-coding gene alignments and find it to produce biologically plausible inferences, for instance, as pertaining to site-specific amino acid constraints, as well as distributions of scaled selection coefficients.In their account of mutational features as well as the heterogeneous regimes of selection at the amino acid level, the modeling approaches studied here can form a backdrop for several extensions, accounting for other selective features, for variable population size, or for subtleties of mutational features, all with parameterizations couched within population-genetic theory.However, these approaches have not yet consolidated results from amino acid level phylogenetic studies showing that selection acting on proteins displays strong site-specific effects, which translate into heterogeneous amino acid propensities across the columns of alignments; related codon-level studies have instead focused on either modeling a single selective context for all codon columns, or a separate selective context for each codon column, with the former strategy deemed too simplistic and the latter deemed overparameterized.


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