Fig. 3. Cloning and mapping of zebrafish hst. (A) An integrated genetic and radiation hybrid (RH) panel map of the telomere of linkage group 5 (LG5), showing selected CA-repeat ‘Z’ markers, and the number of recombinant events detected from 4974 meioses. The position of tbx5 on the RH panel coincides with the critical genetic interval defined by linkage mapping of the hst locus. (B) Sequencing of the tbx5 cDNA reveals a C to T change at base pair 1356 in hst mutant embryos. This mutation changes residue 316 (glutamine) to a premature stop codon. (C) A schematic of the tbx5 cDNA indicating the extent of the T-box domain and the location of the hst stop codon.