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Fig. 3 Facial cartilage reductions in Irx mutants. (A) Ventral views of larvae stained with Alcian Blue (cartilage). Three phenotypic groups were identified in Irx mutants: anterior cartilage loss (left), posterior cartilage loss (middle), and near-complete cartilage loss (right). (B) Summary of genotypes for the indicated phenotypes from a quintuple heterozygous in-cross. P-values report chi-square tests for deviation from the expected 1:2:1 wild type:heterozygous:homozygous Mendelian ratio. (C) Sequential confocal imaging of individual zebrafish shows that reductions of the first and second arches (numbered) precede loss of mandibular cartilages (left), reductions of posterior arches 3-7 precede absence of ceratobranchial cartilages (middle), and reductions of all arches precede severe cartilage loss (right). Genotypes of specific examples are shown. Cb1-5, ceratobranchials 1-5; Ch, ceratohyal; M, Meckel's; ov, otic vesicle; Pq, palatoquadrate. Scale bars: 100 µm.