Mutation model for oligonucleotides fitting a Yule distribution

A spin chain, describing a nucleotides sequence, is identified by the labels of a vector state of an irreducible representation of U_q->0(sl2). A master equation for the distribution function is written, where the intensity of the one-spin flip is assumed to depend on the variation of the labels. The numerically computed equilibrium distribution is nicely fitted by a Yule distribution, which is the observed distribution of the ranked short oligonucleotides frequency in DNA