Abstract: In a method for detecting the presence or absence of a specific restriction site in a nucleic acid sequence an oligonucleotide probe complementary to one strand of the nucleic acid sequence spanning said restriction site is synthesized. The probe is labeled at the end nearer the restriction site. The nucleic acid is hybridized to the probe and a blocking oligomer may be added, if necessary, to prevent non-specific binding of the probe. Subsequent digestion with a restriction enzyme cleaves those oligomers that have hybridized to the nucleic acid and reformed the restriction site. The resulting cut and uncut labeled oligomers are separated and detected based on the type of probe label.The described method may be used to detect sickle cell anemia.