A mutation occurs in Drosophila dsx gene that prevents Tra from binding to the dsx Ribonucleic acid (RNA) transcript. In this mutation, the dsx protein expression has no effect on males. But in females, the phenotypic character is transformed into male phenotype.
The process of splicing in the dsx RNA transcript is altered by Tra protein, which is an alternating splicing factor. A non-specific Messenger Ribonucleic acid or mRNA created by alternate splicing of Tra message in both male and females. The transformer-2 gene and the female- specific tra protein both act together to generate phenotype of the female.
The dsx RNA female- transcript is processed in a specific manner by the presence of both the tra-2 and female-specific tra proteins. If the function of Tra is absent, male specific transcript of dsx is produced. This transcript encodes an active protein. This protein promotes male traits but inhibits female traits.
In other words, one key regulator is the product of the transformer gene. When dsx RNA is not binding with tra, the XX females are transformed into the male phenotype.
In females, a splice occurs in the presence of Tra that incorporates exon 4 of the dsx gene into the mature dsxF transcript not exons 5 and 6. Males lack tra. So this splice does not occur. The dsxM transcript incorporates exon 5 and 6 but not exon 4.