Taq DNA Ligase catalyzes the formation of a phosphodiester bond between juxtaposed 5′ phosphate and 3′ hydroxyl termini of two adjacent oligonucleotides which are hybridized to a complementary target DNA

The ligation will occur only if the oligonucleotides are perfectly paired to the complementary target DNA and have no gaps between them; therefore, a single-base substitution can be detected. Taq DNA Ligase is active at elevated temperatures (45°C-65°C).