To provide a finer-scale analysis of hybridization specificity, we determined the relative frequencies of hybridization specificity ratios in defined bins. There was a similar distribution of specificity ratios for single base substitution and two base deletion probes on both strands ( Figure 3 ). The overall lower hybridization specificities of single base deletion and insertion probes are reflected by the increased frequencies of probes within the lower specificity bins (i.e. <2-fold ratio) and decreased frequencies of probes within higher specificity bins (i.e. >3-fold ratio) on both strands.