Recent duplication, domain accretion and the dynamic mutation of the human genome.

An estimated 5% of the human genome consists of interspersed duplications that have arisen over the past 35 million years of evolution. Two categories of such recently duplicated segments can be distinguished: segmental duplications between nonhomologous chromosomes (transchromosomal duplications) and duplications mainly restricted to a particular chromosome (chromosome-specific duplications). Many of these duplications exhibit an extraordinarily high degree of sequence identity at the nucleotide level (>95%) and span large genomic distances (1-100 kb). Preliminary analyses indicate that these same regions are targets for rapid evolutionary turnover among the genomes of closely related primates. The dynamic nature of these regions because of recurrent chromosomal rearrangement, and their ability to create fusion genes from juxtaposed cassettes suggest that duplicative transposition was an important force in the evolution of our genome.