Scatter plots of the correlation coefficient in function of the KS value of the gene pairs belonging to different functional classes. The full black line represents the local regression (locfit) line fitted to the data of that particular class, together with its 95% confidence interval (dashed line). (a-b) Gene pairs that have diverged quickly after birth have an intercept of the regression line with the y-axis close to zero; (c-d) whereas slow divergence is reflected by an intercept with the y-axis close to one and a steep slope. (e-f) A more average situation can be observed for most classes. Data of the following classes are displayed: (a) signal transduction; (b) response to external stimuli; (c) macromolecule biosynthesis; (d) structural molecule activity; (e) nucleotide binding; (f) regulation of biological process. Plots of other functional classes of genes can be found in Additional data file 3.