Patent ID: 7244562

Claim:
A method of detecting a single nucleotide polymorphism (SNP) in a double stranded target DNA molecule, comprising: (a) providing the following single stranded DNA oligonucleotide probes: (i) a first oligonucleotide probe complementary to a specific region of the target DNA, wherein, when the first probe is paired with said specific region of said target DNA, the 3′ end base of said probe pairs with a base in the target DNA at or immediately adjacent to the site of SNP being detected; (ii) a second oligonucleotide probe complementary to said a specific region of the target DNA, wherein, when the second probe is paired with the specific region of said target DNA, the 5′ end nucleotide of the probe pairs with a base in the target DNA at or immediately adjacent to the site of the SNP being detected; wherein the first and the second probes are complementary to adjacent, but non-overlapping, sequences in the target DNA, such that, when the probes are contemporaneously annealed to the target DNA, the 3′ end of the first probe is paired with the base adjacent to the base to which the 5′ end of said second probe is paired; (b) contacting the first and the second probes, with RecA protein to form RecA filaments; (c) contacting the RecA filaments with the target DNA, thereby forming a three stranded DNA D-loop structure in the target DNA, which D-loop structures comprise the probes and the two strands of the target DNA; (d) contacting the DNA D-loop structure with a DNA ligase, thereby joining the probes to form a ligation product; (e) detecting the presence of said ligation product, the presence of which is indicative of the presence of said SNP.