The flanders locus was mapped to chromosome 6 of the zebrafish genome using a genome-wide panel of SSLP markers for low-resolution mapping. Finer mapping using additional SSLP markers placed flanders in a 2.4 Mb region defined by markers z17212 and z6601. The flanders c.631T>A mutation destroys a DraI site and this was used to create a genotyping screen employing the primers listed in Table S1 available online. The wild-type amplicon cut by DraI produces a 159-bp band; the mutant amplicon not cut by DraI is 213 bp long.