and both sets of probands had similar numbers of children (0.52 vs 0.59, P=0.6). In those instances (21) where it was possible to determine the parental origin, more de novos occurred in the paternal (P=14) than the maternal (n=7) genome but this was not statistically significant (P=0.13). The nonsignificant excess of paternal de novos was largely attributable to CNVs that were not generated by nonallelic homologous recombination, eight such events being observed on chromosomes of paternal origin compared with two on those that were maternally derived, although this is not significantly different from chance (P=0.06).
