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Updated: Jun 10, 2026
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Rare Event Detection Using Error-corrected DNA and RNA Sequencing
Published on: August 3, 2018
Detecting positive selection within genomes: the problem of biased gene conversion
Abhirami Ratnakumar1, Sylvain Mousset, Sylvain Glémin
1Department of Medical Biochemistry and Microbiology, Uppsala University, Box 582, 751 23 Uppsala, Sweden.
Summary
GC-biased gene conversion (gBGC) can mimic positive selection in primates. This recombination process can inflate the non-synonymous to synonymous substitution rate ratio (d(N)/d(S)), potentially misidentifying evolutionary acceleration.
Area of Science:
- Evolutionary genetics
- Genomics
- Molecular evolution
Background:
- Identifying positive selection is crucial for understanding evolution.
- Accelerated evolution can be caused by factors other than positive selection, such as GC-biased gene conversion (gBGC).
- gBGC is a recombination-associated process that biases nucleotide fixation towards G and C, potentially creating bursts of substitutions.
Purpose of the Study:
- To investigate the influence of gBGC on scans for positive selection in primate evolution.
- To determine the extent to which gBGC can explain elevated non-synonymous to synonymous substitution rates (d(N)/d(S)).
- To assess if gBGC can be mistaken for positive selection in coding sequences.
Main Methods:
- Genome-wide scans for positive selection across primate phylogeny.
- Analysis of genomic signatures of gBGC in genes identified by selection scans.
- Maximum-likelihood framework to estimate the contribution of gBGC to elevated d(N)/d(S) ratios.
Main Results:
- Genes identified as targets of positive selection show a significant association with the genomic signature of gBGC.
- gBGC is estimated to account for over 20% of significantly elevated d(N)/d(S) ratios, especially on shorter evolutionary branches.
- gBGC can produce very high d(N)/d(S) values (exceeding 2) in certain cases.
Conclusions:
- GC-biased gene conversion significantly impacts primate coding sequence evolution.
- gBGC frequently generates evolutionary patterns that can be erroneously interpreted as positive selection.
- Revisiting evolutionary analyses to account for gBGC is essential for accurate identification of positive selection.
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