| Abstract
| - By the combination of peptide nucleic acid (PNA) with single-stranded DNA specific nucleases,alteration of a single base to another in DNA has been detected with high accuracy. Only the DNAs inDNA/PNA duplexes involving a mismatch are efficiently hydrolyzed by these enzymes, whereas fullymatching sequences are kept intact. This difference is visually scored by adding 3,3‘-diethylthiadicarbocyanine, which changes its color from blue to purple upon binding to DNA/PNA duplexes. These findingsare applied to the convenient and straightforward detection of single nucleotide polymorphisms (SNPs).When the target site in the sample DNA is completely complementary with the PNA, a notable amount ofDNA/PNA duplex remains and thus the solution exhibits purple color. In the presence of even one mismatchbetween PNA and DNA, however, the DNA is completely digested by the enzyme and therefore the dyeshows its intrinsic blue color. The SNPs in the apolipoprotein E gene of human DNA have been successfullygenotyped by this method.
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