Fig. 6. The fby mutation is a premature stop codon in the tbx2b gene. (A) Diagram of zebrafish chromosome 15, showing the location of the fby mutation relative to nearby SSLP markers. (B) In fby^c144 mutants, the third position of codon 245 in the tbx2b gene was transverted from T to A, generating a stop codon within the T-box sequence. (C,D) Frontal views of 4-dpf larvae. Compared with uninjected foxd3:gfp controls (C), injection of an antisense morpholino against the start codon of tbx2b (ATG MO) resulted in a similar phenotype to the fby mutation (D). Scale bar: 25 µm.