Shadows provide illumination

Comparison of human and mouse DNA sequences has led to the discovery of numerous genes, but is limited by large-scale differences in genomic structure between the organisms. In contrast direct comparisons between humans and primates have been hindered by the very large amount of sequence identity, which can obscure the boundaries of functional regions. In the 28 February Science, Edward Rubin and colleagues at the Lawrence Berkeley National Laboratory, Berkeley, California, US, compared multiple primate genomes to identify exons, regulatory elements, and other features of human genes (Science 229:1391-1394, February 27, 2003).

Rubin et al. compared sequences from more than a dozen primate species, using a technique they call phylogenetic shadowing. While individual species differ little from one another, the additive collective difference of higher primates as a group is comparable to that of humans and mice. In their analysis of differences, they factored in relatedness...