Fig. 5: Huntington’s disease demonstrates a quadratic relationship between severity and variation.

a Huntington’s disease genotypes CAG repeat number) are plotted against severity (age of onset). Significance bars are omitted for clarity; higher numbers of CAG repeats are associated with more severe disease. In box and whisker plot, the box covers the 25th to 75th quartiles, the line is at the median, and whiskers extend to the minimum and maximum values. b Each genotype was plotted by its age of onset as the x-coordinate and variance of age of onset as the y-coordinate. This represents among-individual variation. The R-squared for this relationship is indicated. c Outliers were removed from the dataset plotted in (b), and each genotype was plotted by its age of onset as the x-coordinate and variance of age of onset as the y-coordinate. This represents among-individual variation. The R-squared for this relationship is indicated. The gray bands in (b) and (c) represent 95% confidence intervals.