Schematic of amplification and ligation in the existing oligonucleotide ligation assay (OLA).

The pol gene of HIV DNA is amplified by nested PCR. Note that the HIV DNA gene map positions are not to scale. A portion of the amplicon is mixed with three oligonucleotide probes: a 5’ fluorescein (F) -conjugated mutant (MUT)-specific HIV probe; a 5’ digoxigenin (D) -conjugated wild-type (WT)-specific probe; and a 5’ phosphorylated, 3’ biotin (B) -conjugated common probe. When specific probes are complementary at the mutation site, they are ligated to the common probe to create a DNA strand with labels at both ends. Only ligated products are detected during the CDD procedure (surface capture, denaturation of oligonucleotide from target DNA, and enzyme-based detection).