  Based on the concept of DNA strand displacement and DNA strand algebra we
have developed a method for logical inference which is not based on silicon
based computing. Essentially, it is a paradigm shift from silicon to carbon. In
this paper we have considered the inference mechanism, viz. modus ponens, to
draw conclusion from any observed fact. Thus, the present approach to logical
inference based on DNA strand algebra is basically an attempt to develop expert
system design in the domain of DNA computing. We have illustrated our
methodology with respect to worked out example. Our methodology is very
flexible for implementation of different expert system applications.
