Fig. 3. Dilute lethal mutants have abnormal photoreceptor synapses. Transmission electron micrographs of synaptic regions. Ribbon synapses (arrows) look normal in the control mice (A). In Myo5a^d-l/Myo5a^d-l mice, the ribbons of photoreceptor synapses appear club-like (B,E), although the ribbons of bipolar cell synapses appear normal (G). Photoreceptor synapses of Myo5a^d-l/Myo5a^d-l mutants also possess clusters of presumed synaptic vesicles that are ectopically located (C,D,F, arrows). At least three sections were examined from each of four Myo5a^d-l/Myo5a^d-l mice (abnormalities were consistently observed in the mutant mice) and two control mice (Myo5a^d/Myo5a^{d or d-l}; the synaptic morphology of these mice is similar to all wild-type mice we have previously examined, this dilute genotype does not affect synaptic morphology, which would be expect from their ERGs). Scale bars, 100 nm (F), 300 nm (others).