Single Base Extension

Single Base Extension (SBE) is a method for determining the identity of a nucleotide base at a specific position along a nucleic acid. The method is used to identify a single nucleotide polymorphism (SNP).

In the method, invented by Phillip Goelet, Michael Knapp and Stephen Anderson while at Molecular Tool, an oligonucleotide primer hybridizes to a complementary region along the nucleic acid, to form a duplex, with the primer’s terminal 3’ end directly adjacent to the nucleotide base to be identified. The oligonucleotide primer is enzymatically extended a single base by a nucleotide terminator complementary to the nucleotide being identified. The terminator prevents additional nucleotides from being incorporated.

Many different approaches can be taken for determining the identity of a terminator, including fluorescence labeling, mass labeling for mass spectrometry, measuring enzyme activity using a protein moiety, and isotope labeling.