Average exonuclease removal from gene subgroups. The average exonuclease removals from gene ends was investigated for each IGHV, IGHD and IGHJ subgroup. Significant differences were seen among the 294 IGHV genes (A). No significant difference between the 245 IGHD genes were seen at the 5' end (B). The 3' IGHD end does show significant differences for the IGHD subgroups (C) as do the six IGHJ subgroups (D). Bars represent standard error.