A cascade of alternative RNA splicing regulates sex determination in Drosophila

Three pre-mRNAs of major Drosophila sex-determining genes are alternatively spliced. The female-specific pathway is shown on the left and the male-specific pathway shown on the right. The pre-mRNAs are identical in both sexes and shown in the middle. In the male Sex-lethal and transformer mRNAs, there are stop codons that terminate translation. These sequences are removed by splicing to produce functional proteins in the female. The Transformer and Tra-2 proteins then splice the female doublesex pre-mRNA to produce the female-specific isoform of the Dsx protein, which differs from the male-specific isoform by the alternative splicing of several exons.