Evolutionary determinants of genome-wide nucleotide composition.

Area of Science:

• Evolutionary genomics
• Molecular evolution

Background:

• Phylogenetic diversity in genome nucleotide composition (G+C vs. A+T) is a long-standing evolutionary genomics mystery.
• Potential drivers include interspecific differences in mutation bias and/or selection efficiency.

Purpose of the Study:

• To investigate the relative contributions of mutation bias, selection, and gene conversion to genomic G+C composition.
• To determine if G+C composition at specific genomic sites deviates from neutral expectations.

Main Methods:

• Analysis of genomic data to assess nucleotide composition patterns.
• Comparative genomics approaches to infer evolutionary forces.

Main Results:

• Genomic G+C composition is significantly driven by mutation bias.
• Direct selection and biased gene conversion also substantially modify G+C content.
• G+C composition at fourfold redundant sites is elevated above neutral expectations.

Conclusions:

• Both mutation bias and selection/gene conversion play crucial roles in shaping genome nucleotide composition.
• Elevated G+C content at fourfold redundant sites suggests specific evolutionary pressures.