Fig. 4. String/Cdc25 phosphatase levels are regulated by the APC/C activator Fizzy-related/Cdh1. The levels of String/Cdc25 phosphatase in embryo extracts after the stage of mitosis 16 were analyzed by immunoblotting with antibodies against String (STG) and tubulin (TUB) to control for loading. Extract from 60 embryos was loaded in each of the lanes except for lanes 3-5, which contain a threefold dilution series of the extract loaded in lane 2. The embryos loaded in lanes 8 and 9 were exposed to a heat shock (+HS) before extract preparation. The following genotypes were analyzed: fzr^G0326 (lane 1, fzr^G), fzr^ie28 (lanes 2-5, fzr^ie28), w¹ (lane 6 and 9, control) and Hs-stg (lane 7 and 8, Hs-stg). Comparison of anti-STG signal intensities indicates that the levels of String/Cdc25 phosphatase are at least 10-fold higher in fzr mutant embryos.