Self-similarity in complete genomes

Recently it was reported that in terms of the global feature of frequency distributions of short words, whole genomes are equivalent to random sequences of a much shorter length which, for given word length, is genome independent, or universal. For two-letter words the universal equivalent random-sequence length was found to be about 300 bases. Here we show that as a rule whole genomes are highly self-similar in exhibiting this universal property. For two-letter words, with few exceptions any segment more than ∼1000 bases from any genome possesses the same universal property. The universality and self-similarity taken together suggest genomes are close to being selforganized critical systems. We show that a model in which genomes grow by maximally stochastic segmental duplication will generate sequences that share the univrersal and self-similar properties of genomes.