CNVs in the control sibling group, we apply the formula (Bunge and Fitzpatrick, 1993) C = c/u + g2*d*(1-u)/u, in which c = the total number of distinct species observed; c1= the number of singleton species; d = total number of CNVs observed; g = the coefficient of variation of the fractions of CNVs of each type, and u = 1 – c1/d. (In this calculation, due to the small number of observations, we assume that g equals 1.) For the de novo events in siblings, c1=14, c=15, d=16 and C=232. This calculation is performed in the siblings because the observed rare de novo CNVs in this group are assumed to be predominantly non-risk variants and consequently represent the null distribution.
