“…In some experiments, RNA-DNA hybridization was quantified by cutting the hybrid dots from the nitrocellulose filter, drying under a heat-lamp, and counting bound radioactivity in toluene-based scintillation fluid. In situ hybridization Tissues from 14th day embryos were fixed by the Sainte-Marie technique with Engelhardt's modification (Engelhardt et al, 1971;Dziadek and Adamson, 1978), and subsequently embedded in paraffin wax. 8 pm sections were mounted onto gelatinized microscope slides, dried, de-paraffinized in toluene, and hydrated to 3 x SSC before hybridization.…”