  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
