Dade Behring Inc.

Marc Taylor

Nurith Kurn

Alla Lishanski

Yen Ping Liu

A method is disclosed for detecting the presence of a difference between two related nucleic acid sequences. In the method a complex is formed comprising both strands of each sequence. Each member of at least one pair of non-complementary strands within the complex have labels. The association of the labels as part of the complex is determined as an indication of the presence of a difference between the two related sequences. The complex generally comprises a Holliday junction. In one aspect a medium suspected of containing said two related nucleic acid sequences is treated to provide partial duplexes having non-complementary tailed portions at one end. The double stranded portions of the partial duplexes are identical except for said difference. One of the strands of one of the partial duplexes is complementary to one of the strands of the other of the partial duplexes and the other of the strands of one of the partial duplexes is complementary to the other of the strands of the other of the partial duplexes. The medium is subjected to conditions that permit the binding of the tailed portions of the partial duplexes to each other. If there is a difference in the related nucleic acid sequences, a stable complex is formed comprising a Holliday junction. If no difference exists, the complex dissociates into duplexes. A determination is made whether the stable complex is formed, the presence thereof indicating the presence of the related nucleic acid sequences. The method has application in detecting the presence of a mutation in a target sequence or in detecting the target sequence itself. Also provided is an alternative primer scheme which allows for the reduction of background signal due to mis-priming during amplification of the nucleic acid sequences in the detection method described herein.

Detection of differences in nucleic acids by inhibition of spontaneous DNA branch migration

The present invention relates to a method for selectively extending an oligonucleotide primer along a specific target polynucleotide sequence in a mixture of polynucleotides. A combination is provided comprising the mixture, an oligonucleotide primer having a modification, and a binding substance for the modification wherein the binding substance binds to the oligonucleotide and prevents the extension of the oligonucleotide along the target polynucleotide sequence. The temperature of the combination is adjusted to a level sufficient to irreversibly denature the binding substance and permit the extension of the oligonucleotide primer along the specific target polynucleotide sequence. The invention has particular application in the amplification of nucleic acids. Also disclosed are kits for carrying out a method in accordance with the present invention.

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Mountain View, CA, United States of America

Marc Taylor