Figure 1. Heteroduplex formation producing mismatched base pairs is essential for many mutation detection methods. Hybridization of mutant and wild-type sequences is shown to produce two complementary heteroduplexes, and the original homoduplexes reform. Full lines represent the DNA sequence.

Figure 2. Schematic representations of methods to detect unknown mutations: (a) ribonuclease; (b) denaturing gradient gel electrophoresis; (c) single-strand conformation polymorphism; (d) heteroduplex; (e) enzyme and chemical cleavage of mismatch; (f) protein truncation test. Full lines represent the DNA sequence (except where RNA is indicated by R). Mutations are represented by an X. Arrows represent cleavage.

Figure 3. Schematic representation of methods to detect known mutations: (a) restriction enzyme cleavage; (b) allele-specific oligonucleotide; (c) primer extension; (d) allele-specific amplification; (e) oligonucleotide ligation; (f) Taqman. Full lines represent the DNA sequence. Mutations are represented by an X. L and F represent labels, usually fluorescent, and Q, a quencher. Diagonal arrow represent cleavage.