In contrast to single nucleotide mismatches, detailed thermodynamic analyses of double helical nucleic acids with bulged nucleotides have only recently been conducted (34, (39) (40) (41) . In such cases, the bulged nucleotide is unpaired on only one of the nucleic acid strands. These studies are relevant to understanding the properties of the deletion and insertion probes since they can form duplexes containing bulges with target nucleic acid. For deletion probes, the bulged nucleotide is located on the target strand ( Figure 7) . Conversely, the insertion probes contain the bulged nucleotide in duplexes with wild-type target (Figure 7) .