Fig. 1. (A) Amplification profiles for Tbx5/Tbx4 and ß-actin. The intensity of PSL of each band was measured using a molecular imager system and plotted on a semilogarithmic scale against the cycle number. The black square depicted in each graph indicates the cycle number used for quantitative analysis of each gene expression. Two independent sets of experiments using different RNAs gave essentially the same results. (B) Tbx5/Tbx4 expression in the presumptive wing region and the wing bud from embryos of stages 9-23. (C) Tbx5/Tbx4 expression in the presumptive leg region and the leg bud from embryos of stages 9-23. (D,E) The relative amount of Tbx expression after being standardized with ß-actin. The expression of each gene in the presumptive limb region at stage 9 was taken as 1.0.