Abstract
We determine the Rényi entropies Kq of symbol sequences generated by human chromosomes. These exhibit non-trivial behaviour as a function of the scanning parameter q. In the thermodynamic formalism, there are phase-transition–like phenomena close to the q=1 region. We develop a theoretical model for this based on the superposition of two multifractal sets, which can be associated with the different statistical properties of coding and non-coding DNA sequences. This model is in good agreement with the human chromosome data.