Figure 7.—

Analysis of D. melanogaster mRNAs showing that exon Z is not sex specific and is disproportionately expressed in heads. Primers for this RT–PCR analysis are positioned on the Sxl schematic and described in materials and methods. The pair used for each gel is indicated. One mRNA preparation was used for the two gels on the left and another for the two gels on the right. Estimated sizes of the bands are consistent with expectations for Exon Z mRNAs being generated in both sexes by a 1-Z-4-5 splicing pattern that skips the male-specific exon 3. Predicted sizes of the various RT–PCR products are presented in materials and methods. The CF primer pair indicated that exon Z mRNA is not present in D. melanogaster ovaries. The same was found to be true for the scuttle fly (Sievert et al. 2000).