Fig. 6. The Mad-Zen interaction is necessary for Race activation. Late stage 5 embryos were hybridized in situ with a Race probe (A,B) or Race and lacZ probes (to determine the zen mutant embryos; C,D). (A) Embryo expressing UAS-zen driven by the maternal Gal4 driver. Ectopic Race expression is visible in the posterior region and the dorsal stripe is broader. (B) Embryo expressing UAS-zen-Del driven by the maternal Gal4 driver. Ectopic Race transcripts are absent. (C) zen^w36 mutant embryo expressing UAS-zen driven by the maternal Gal4 driver. Race expression is restored. (D) zen^w36 mutant embryo expressing UAS-zen-Del driven by the maternal Gal4 driver. Race expression is absent, indicating that Zen-Del is not able to rescue the zen mutant phenotype.