Figure 4.

Schematic diagrams for the Ligation Detection Reaction (LDR) processes. DNA fragments from the normal type and the mutant type (at the single nucleotide polymorphism (SNP) site) are shown as reaction templates. (1) The denaturation process is the same as in Figure 3 (1). (2) Hybridization: two oligonucleotide probes, complementary to the normal-type target, hybridize to the target DNA fragment. (3) Ligation: adjacent probes that are perfectly complementary to the target (left) are connected by DNA ligase, and thermocycling linearly amplifies the amount of product formed. In the case of the mutant type template, the presence of a single-base mismatch at the junction inhibits the ligation, and therefore no ligated LDR probes are formed (right).