GC content elevates mutation and recombination rates in the yeast .

The chromosomes of many eukaryotes have regions of high GC content interspersed with regions of low GC content. In the yeast , high-GC regions are often associated with high levels of meiotic recombination. In this study, we constructed genes that differ substantially in their base composition [ (31% GC), (43% GC), and (63% GC)] but encode proteins with the same amino acid sequence. The strain with had an approximately sevenfold elevated rate of mutations compared with the strains with or About half of these mutations were single-base substitutions and were dependent on the error-prone DNA polymerase ζ. About 30% were deletions or duplications between short (5-10 base) direct repeats resulting from DNA polymerase slippage. The gene also had elevated rates of meiotic and mitotic recombination relative to the or genes. Thus, base composition has a substantial effect on the basic parameters of genome stability and evolution.