Excess of rare PRDM9 alleles in parents from the FCALL cohort. (A) Pie charts showing frequencies of PRDM9 zinc-finger (ZnF) alleles obtained through Sanger sequencing of 26 parents of patients with B-ALL and 76 parents from the FC family cohort (controls). Alleles labeled as “Others” are population-specific alleles. Individuals' alleles are detailed in Supplemental Tables S3, S5. (B) Differences in allele frequencies between parents of patients and controls. The P-value in parentheses was calculated by including alleles inferred from exome sequencing reads for the 20 ALL parents for which PRDM9 ZnF arrays were not re-sequenced by Sanger (Supplemental Table S4). Applying a Bonferroni correction for performing the same test in two subsets of alleles (non-A and k-fingers alleles) would yield α = 0.025, although this correction is particularly conservative since subsets are correlated. (C) Allelic structure of PRDM9 ZnF array for alleles found in these cohorts (population-specific alleles not shown).