Table 6. The effect of removal of 63 cDNAs linked to high exonuclease activity to the frequency of IGHD segments in bovine fetal immunoglobulin cDNAs.
| IGHD | High exo | Normal exo | Sum |
| IGHDS1 | 1 | 3 | 4 |
| IGHDS2 | 31 | 10 | 41 |
| IGHDS3 | 7 | 85 | 92 |
| IGHDS4 | 0 | 24 | 24 |
| IGHDS5 | 14 | 254 | 268 |
| IGHDS6 | 0 | 1 | 1 |
| IGHDS7 | 0 | 79 | 79 |
| IGHDS8 | 0 | 71 | 71 |
| IGHDS9 | 0 | 9 | 9 |
| IGHDS10 | 0 | 3 | 3 |
| IGHDS11 | 5 | 4 | 9 |
| IGHDS12 | 2 | 7 | 9 |
| IGHDS13 | 0 | 3 | 3 |
| IGHDS14 | 3 | 29 | 32 |
| Sum | 63 | 582 | 645 |
Exonuclease activity was deduced from the alignments with the best matching IGHD segment and quantified by the number of apparently excised nucleotides. High exonuclease activity: excision of over 29 nucleotides from either end of the IGHD segment.