The oligonucleotide ligation assay (OLA) is a genotypic assay which has been used to identify point mutations in DNA for a variety of diseases and to detect drug resistance-associated mutations in HIV-1 subtype B

Principle of Oligonucleotide ligation assay

The target DNA sequence is PCR-amplified prior to the ligation step of the annealed probes. One of the detection probes consists of a sequence complementary to the target sequence (polymorphic site at the 3 end if SNP identification is needed) and also an additional TAG tail sequence. The second detection probe is fully complementary to the target sequence and serves as a reporter due to its fluorescent label at the 3 end. Detection probes bind next to each other, DNA ligase recognizes the nick and makes a bond. The product is captured by anti-TAG on the microsphere surface.