GC bias -the Achilles’ heel of Natural Selection

"GC bias" causes "Codon bias." it is the Achilles heel of the genome. It is the final nail in Natural Selections' coffin.

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"Several criteria can discriminate between the natural selection and biased gene conversion models.

These criteria suggest that the recently reported human accelerated regions (HARs) are most likely the result of biased gene conversion, a natural cellular mechanism not connected with natural  selection.

These regions, far from contributing to human adaptation {Natural Selection}, might represent the Achilles’ heel of our genome." 

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In other words what we thought was natural selection was actually a teleological cellular mechanism of the cell from the beginning of life. It allows rapid change and adaptation outside of natural selection. 

Sorry Charlie (Darwin)

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The article "Adaptation or biased gene conversion? Extending the null hypothesis of molecular evolution" by Nicolas Galtier and Laurent Duret discusses the two main mechanisms that can lead to an accelerated rate of evolution: natural selection and biased gene conversion.

Natural selection is the process by which favorable mutations become more common in a population over time. This can happen when a mutation provides an individual with a reproductive advantage, such as making it more likely to survive or reproduce.

Biased gene conversion is a process that can lead to the rapid spread of mutations within a genome. It occurs when homologous DNA sequences are copied from one another, and the copying process is not always accurate. This can lead to the spread of advantageous mutations, even if they are not under selection.

The authors of the article argue that biased gene conversion is a more likely explanation for the accelerated rate of evolution seen in some regions of the genome. They point to several lines of evidence, including the fact that biased gene conversion is more likely to occur in GC-rich regions, which are also the regions that show the most accelerated rate of evolution.

The authors also argue that biased gene conversion can explain the existence of human accelerated regions (HARs). HARs are regions of the genome that have evolved more rapidly in humans than in other primates. The authors suggest that HARs may have arisen as a result of biased gene conversion, which could have been driven by natural selection or by other factors, such as gene duplication.

The article by Galtier and Duret provides a new perspective on the process of molecular evolution. It suggests that biased gene conversion may be a more important factor than previously thought in driving the evolution of the genome.

Here are some additional thoughts on the topic:

  • Biased gene conversion is a relatively new discovery, and there is still much that we do not know about it. However, it is a fascinating process that has the potential to shed light on many aspects of molecular evolution.

  • The study of biased gene conversion is still in its early stages, but it has already had a significant impact on our understanding of how the genome evolves. As we learn more about this process, it is likely to become even more important in our understanding of evolution.

Article snippets

Adaptation or biased gene conversion? Extending the null hypothesis of molecular evolution

https://doi.org/10.1016/j.tig.2007.03.011

The analysis of evolutionary rates is a popular approach to characterizing the effect of natural selection at the molecular level.

Sequences contributing to species adaptation are expected to evolve faster than nonfunctional sequences because favourable mutations have a higher fixation probability than neutral ones.

Such an accelerated rate of evolution might be due to factors other than natural selection, in particular GC-biased gene conversion.

This is true of neutral sequences, but also of constrained sequences

Several criteria can discriminate between the natural selection and biased gene conversion models.

These criteria suggest that the recently reported human accelerated regions are most likely the result of biased gene conversion.

We argue that these regions, far from contributing to human adaptation, might represent the Achilles’ heel of our genome.

From a population genetics point of view, the BGC meiotic drive is essentially equivalent to directional selection

Under the BGC model, AT → GC mutations have a higher probability to be transmitted to the next generation, and eventually fixed, than is the case for other mutations (GC → AT, AT → TA or GC → CG).

an episode of BGC should therefore result in an increased substitution rate,

BGC, similarly to adaptation, can result in a sudden increase in substitution rate in nonfunctional, but also in functional, regions

several aspects of the evolution of HARs seem to be consistent with the BGC model,

substitutions that have accumulated in the human lineage are mostly AT → GC changes

BGC substitution hotspots: genomic Achilles’ heel

BGC can lead to lineage-specific increases in substitution rate in functional sequences in the absence of adaptation

Moreover, several features of the HARs seem to be more consistent with the BGC model than with selective scenarios


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