The capacity of string-duplication systems

It is known that the majority of the human genome consists of repeated sequences. Furthermore, it is believed that a significant part of the rest of the genome also originated from repeated sequences and has mutated to its current form. In this paper, we investigate the possibility of constructing an exponentially large number of sequences from a short initial sequence and simple duplication rules, including those resembling genomic duplication processes. In other words, our goal is to find out the capacity, or the expressive power, of these string-duplication systems. Our results include the exact capacities, and bounds on the capacities, of four fundamental string-duplication systems.