Genetic analysis of Drosophila has shown that a morphogenetic gradient of the Transforming Growth Factor‐β family member dpp patterns the embryonic dorsalventral axis. Molecular and embryological evidence from Xenopus has strongly suggested a similar role for Bmp‐4, the dpp homolog, in patterning the dorsalventral axis of chordates. A recent report has now identified mutations in two genes, dino and swirl, that disrupt dorsal‐ventral patterning in the zebrafish Danio rerio(1). Characterization of these mutations parallels findings from Drosophila, thus establishing a genetic (...) framework for the analysis of dorsalventral patterning in a vertebrate. (shrink)