Abstract: A method for detecting mutations, such as a single base change or an addition or deletion of about one to four base pairs, is based on the use of an immobilized DNA mismatch-binding protein, such as MutS, which binds to a nucleic acid hybrid having a single base mismatch or unpaired base or bases, thereby allowing the detection of mutations involving as little as one base change in a nucleotide sequence. Such a method is useful for diagnosing a variety of important disease states or susceptibilities, including the presence of a mutated oncogene and the presence of DNA containing triplet repeat sequences which characterize several genetic diseases including fragile X syndrome. The present method is used to isolate or remove by affinity chromatography duplex DNA molecules containing mismatches such as error-containing molecules in PCR-amplified DNA samples. Methods for detecting and enriching minority sequences are disclosed.

Abstract: A method for detecting mutations, such as a single base change or an addition or deletion of about one to four base pairs, is based on the use of an immobilized DNA mismatch-binding protein, such as MutS, which binds to a nucleic acid hybrid having a single base mismatch or unpaired base or bases, thereby allowing the detection of mutations involving as little as one base change in a nucleotide sequence. Such a method is useful for diagnosing a variety of important disease states or susceptibilities, including the presence of a mutated oncogene and the presence of DNA containing triplet repeat sequences which characterize several genetic diseases including fragile X syndrome. The present method is used to isolate or remove by affinity chromatography duplex DNA molecules containing mismatches such as error-containing molecules in PCR-amplified DNA samples. Also provided are compositions and kits useful for practicing the methods of the present invention.