The functional repertoires of metazoan genomes.
Metazoan genomes are being sequenced at an increasingly rapid rate. For each new genome, the number of protein-coding genes it encodes and the amount of functional DNA it contains are known only inaccurately. Nevertheless, there have been considerable recent advances in identifying protein-coding and non-coding sequences that have remained constrained in diverse species. However, these approaches struggle to pinpoint genomic sequences that are functional in some species but that are absent or not functional in others. Yet it is here, encoded in lineage-specific and functional sequence, that we expect physiological differences between species to be most concentrated.