A PROPOSAL ON METRICS FOR IDENTIFICATION USING NUCLEIC-ACID SEQUENCES

The need is stressed for attempts to be made to permit diagnostic nucleic acid sequences to be used in a quantitative manner. Sequence differences or binding values should be converted to a distance measure and from this an ultrametric tree should be constructed. A single quantitative determination can yield considerable information about the likely identity of an unknown microorganism when the distance obtained from the sequence is compared with the tree. The concept is illustrated by hypothetical species and genus subsequences, and it is suitable both for successive use of hierarchical subsequences and for automated identification. It is pointed out that entirely specific subsequences for higher taxa may be difficult to discover. These principles will be useful for the future design of diagnostic sequences, including possible application to DNA-DNA pairing.