Study on the isentropic equations of nucleotide sequences and their application

The tetrahedral representation of DNA sequences and its applications have been studied by many authors. In this paper we study the isentropic equations of DNA sequences and their application. First, the DNA sequence entropy is introduced, and the entropy current and divergence are defined. Second, the isentropic equations are deduced and the isentropic curves on the three coordinate planes are respectively drawn by a computer. Third, an analysis is given on the entropy distribution on the coordinate planes. Finally, we make use of the results to discuss the relationship of the fastest increasing directions of the entropy for the cytochrome c genes of seven species.