As expected from Table 1 and Figure 3 , the two base deletion probes consistently showed a higher average hybridization specificity ratio followed by single base substitution, single base deletion and single base insertion probes on both strands of exon 50 ( Figure 4) . Nevertheless, the hybridization specificity ratios for all classes of mismatch probes fluctuate across the exon 50 sequence (Figure 4 ). For example, two base deletion probes showed a peak value of 6.76 (unlogged) centered at base 7071 and a trough value of 1.90 (unlogged) centered at base 7002 on the sense strand. We also found similar fluctuations in specificity ratios for all mismatch probe types in the remaining 61 ATM coding exons (Supplementary Figure 1 ).