Expression of reference genes (A-E) and genes showing stage-associated differential display RT-PCR patterns (F-H) obtained by qPCR. Histograms show normalized relative gene expression in Pietrain and Duroc embryos/Musculus longissimus dorsi at seven prenatal stages and in the adults (primary y-axis). For some genes data on expression in adults is missing. Open boxes and diamonds show absolute values of the Pietrain vs. Duroc expression ratios at each stage (log2(Pi/Du)). Open diamonds indicate higher expression in Duroc compared to Pietrain individuals and open boxes indicate the reverse situation (secondary y-axis).