Fig. 6. Race expression in dorsalized embryos injected with different amounts of sog or chordin mRNAs. Embryos laid by snk females were injected with decreasing amounts of sog mRNA (A-E) or chordin mRNA (F-H) and stained after injection for Race expression (blue). Each embryo illustrates the most frequent outcome after the injection of a particular mRNA concentration, the total numbers are given in Table 2 for sog mRNA and Table 3 for chd mRNA. Injections were performed in an anterior dorsal position (similar to that in Fig. 5) and the size of the bolus of injected mRNA was held constant in all injections. (A) Lateral view of an embryo injected with 40 µg/µl of sog mRNA. The inhibition of endogenous Race expression is strong and no ectopic Race expression is observed. (B) Lateral view of an embryo injected with 0.8 µg/µl of sog mRNA. Race expression is inhibited at the site of injection and ectopic Race expression is detected at a distance from the site of injection. (C) Dorsal view of the embryo shown in B. (D) Dorsal view of an embryo injected with 0.2 µg/µl of sog mRNA. Race expression is inhibited locally but no ectopic expression is observed. (E) Dorsal view of an embryo injected with 0.08 µg/µl of sog mRNA. No inhibition of Race is observed. (F) Lateral view of an embryo injected with 4.5 µg/µl of chd mRNA showing complete inhibition of Race expression. (G) Dorsal view of an embryo injected with 2.25 µg/µl of chd mRNA showing local inhibition but no ectopic expression of Race. (H) Dorsal view of an embryo injected with 1.5 µg/µl of chd mRNA. No inhibition of Race expression is observed.