Allele-specific ligation is the technique permitting discrimination of two allele at locus by giving two short synthetic oligonucleotides which would bind ajjacent to teach other on amplified DNA fragment, and would be ligated in the presence of DNA ligase; if one of alleles comprising mutation overlapped by 3'-end of one oligonucleotide, its ligation to oligonucleotide bound 3' to it would be prevented; to deduce the identity of the unknown allele, differentially labelled oligonucleotide pairs might be designed for each allele and their ligation efficiency compared in the presence of unknown allele.