Figure 9: Comparison of (G+C) and gene content in mouse and human.

a, Scatter plot of mouse (y axis) compared with human (x axis) (G+C) content for all non-overlapping orthologous 100-kb windows. In general, (G+C) content is correlated between the two species, but very few mouse windows have a (G+C) content over 55%, even where the related human window has over 60% (G+C) content. b, Average mouse (G+C) content of 100-kb syntenic windows binned by human (G+C) content (1% intervals). The red line indicates median values with standard deviation and 5% (green) and 95% (blue) confidence intervals. The black line indicates identical (G+C) content in orthologous segments. c–e, Gene content increases with (G+C) content when comparing (G+C) and gene content in 320-kb non-overlapping, unmasked windows for mouse (blue lines) and human (red lines). c, Cumulative proportions of genes (solid lines) and genome (dashed lines) having (G+C) content below a given level. The tighter distribution of (G+C) content in mouse results in the curve for mouse crossing that for human at 45–46% for both genes and total sequence. The tendency for both genomes to be gene-poor at low (G+C) content and gene-rich at high (G+C) content is shown directly in d, which shows the fraction of genes residing within the portion of the genome having (G+C) content below a given level (for example, the half of the genome with the lowest (G+C) content contains 25% of the genes). e, The average number of genes per window is plotted against the (G+C) content of the window for both genomes, showing that the gene density in mouse reaches the same level as in human but at a lower level of (G+C) content.