Jeffery, William RWith the advent of gene-expression profiling, a large number of genes can now be investigated simultaneously during critical stages of development. This approach will be particularly informative in studies of ascidians, basal chordates whose genomes and embryology are uniquely suited for mapping developmental gene networks.en-USNotochord CellAncestral ChordateNotochord DifferentiationChordate FeatureTunicate GenomeArticle