Abstract: A method for analyzing a sample oligonucleotide sequence is described. The method comprises contacting the sample oligonucleotide sequence with an anchor sequence which comprises an immobilized oligonucleotide sequence which hybridizes with the sample. The sample is also contacted with a probe comprising an oligonucleotide sequence which hybridizes to a target oligonucleotide sequence to be detected in a suitable buffer to form a complex. The complex is subjected to a field which moves unbound oligonucleotide sequences away from the anchor sequence in the direction of the field, and preferably, extends the sample sequence. Whether the probe is bound to the sample oligonucleotide sequence, and preferably, the position of the probe, is determined to determine whether the target oligonucleotide sequence is present in the sample. The method can be used for mapping, for identity typing, and to determine whether a test oligonucleotide sequence is present in the sample.