File:Scatter plots with linear regression line on parental ages and their respective number of de novo mutations.jpg

English: Scatter plots with linear regression line on parental ages and their respective number of de novo mutations (DNMs) in the 61 trios with Illumina sequencing data. (a) The number of DNMs of paternal origin is plotted against the father’s age (in years). The blue line shows the linear fit (estimate of the slope=0.31, P=5.15 × 10⁻⁴) and the grey band represents the 95% confidence interval. (b) The number of DNMs of maternal origin is plotted against the mother’s age (in years), the blue line shows the linear fit (estimate of slope=0.12, P=0.02), and the grey band represents the 95% confidence interval.

On average, the father transmits 3.44 times more DNMs than the mother does (that is, on average, 78% of the total number DNMs came from the father and 22% of those came from the mother, although the proportion of DNMs of paternal origin varies between 0.5 and 1). This ratio is consistent with previous studies, 3.9 reported by Kong et al. and 3.1 by Francioli et al. Following this, we fit simple linear regression models to the normalized number of DNMs (observed number divided by the proportion of DNMs phased for the proband) from the father and the mother with their respective ages. The father’s age is significantly correlated with the number of DNMs passed on from the father (estimated increase in rate per year=0.31, P=5.15 × 10−4, simple linear regression). Furthermore, our analysis indicated that the mother’s age also shows a correlation with the number of DNMs passed on from the mother (estimated increase in rate per year=0.12, P=0.02).