Breeding scheme for the production of insertional mutants in zebrafish. Single-cell to blastula-stage embryos are injected with a mutagen and grown to adulthood. The mature fish are then inbred twice to produce first an F1 and then an F2 generation. Mutants with behavioural phenotypes (black and blue spotted fish) can be identified by in-crossing the F3 fish. The number- and position of insertions can be monitored by western blot and PCR analysis.