The identification of genes via their mutant phenotypes is the most di
rect way of dissecting the molecular basis of developmental processes.
While this approach has been extremely powerful in invertebrates such
as Drosophila and Caenorhabditis elegans, it has until recently been
lacking in vertebrates. Now two landmark studies by the groups of Nuss
lein-Volhard and Driever have for the first time provided the basis fo
r a comprehensive genetic dissection of vertebrate development using t
he teleost fish, Danio rerio. The mutations identified in these screen
s look set to revolutionise our understanding of vertebrate developmen
t.