To explain its origin and evolution, mainly three mechanisms have been proposed: selection for GC content, mutation bias, and GC-biased gene conversion.
There are, for instance, correlations between recombination rate, GC content, mutation rate, and rate of biased gene conversion that remain to be elucidated (Hardison et al. 2003; Duret 2006; Duret and Arndt 2008).
The biological characteristics of the primary tumor play an important role in determining the outcome of the disparity, and significant differences have been identified between African American and Caucasian breast cancer in steroid receptor and growth factor receptor content, mutations in cell cycle components, chromosomal abnormalities, and tumor suppressor and other cancer genes.
I understand and agree with the results presented, i.e. the nucleotide and codon compositions are influenced by GC% and purine content (AG%), but it is not clear to me how the authors can link GC% with mutations, and purine content variation with selections.
KRAS mutations were detected in many samples with a very low tumor cell count, and the frequency of KRAS codon 12 or 13 mutations in tissues with a low (< 10%) tumor cell content (36% mutation rate) was similar to that of tissues with ≥10% tumor cells (37% mutation rate).
In the end, high-depth sequencing of the mitochondrial genome of Vigna, or any of the growing number of seed plants without large repeats, will ultimately show whether mitochondrial recombinational activity is as notoriously variable across seed plants as are mitochondrial genome size and sequence content [1], mutation rate [39], and RNA editing frequency [40].
It is possible that GC content and mutation rates of genes may have a role in modulating correlated evolution of codon and intron sequences among the species.
The Human Genome Variation Society HGVSS) has proposed a recommendation for the nomenclature of genetic variations and content of mutation databases and scientific publications (36).
This suggests that the lower amount of introns in A. gambiae than that of A. aegypti and C. quinquefasciatus may have an association with differential GC content and mutation rates of genes among these mosquitoes.
Seven independent wild-type RS2 and nine independent mutant RS2 plants were selected to negate the action of unidentified genes that may contribute to the oligosaccharide content; the mutation density was previously determined to average 1/550 kilobases [ 4].
In mammalian genomes, PARs have several interesting properties including increased GC content, higher mutation rates and a level of recombination higher than in the rest of the genome [ 18, 19] due to the necessity for crossing over in this region [ 20].
