Abstract
We propose a simple algorithm for estimating the number of nucleotide differences between a pair of RNA or DNA sequences through comparison of their RNAse A mismatch cleavage patterns. In the RNAse A mismatch cleavage technique two or more sample sequences are hybridized to the same RNA probe, the hybrids are partially digested with RNAse A, and the digestion products are compared on an electrophoretic gel. Here we provide an algorithm for converting the numbers of unique and matching electrophoretic bands into an estimate of the number of nucleotide differences between the sequences. Computer simulation indicates that the proposed method yields a robust estimate of the genetic distance despite stochastic errors and occasional violation of certain assumptions. Our study suggests that the method performs best when the distance between the sequences is < 15 differences. When the sequences under analysis are likely to have larger distances, we advise to substitute one long riboprobe with a set of shorter nonoverlapping probes. The new algorithm is applied to infer the proximity of several strains of pseudorabies virus.