Practice question

Active Sex-lethal gene in Drosophila initiates cascade culminating in female development. Sxl protein functions only in XX embryos where early burst of transcription overcomes splicing block, establishing positive autoregulatory loop maintaining female-specific Sxl mRNA lacking male exon with stop codon. Sxl then directs splicing of transformer into functional Tra protein which together with Tra2 drives female-specific splicing of doublesex and fruitless producing DsxF and FruF. DsxF governs yolk protein synthesis, female genitalia, receptivity and repression of male structures, establishing morphological and behavioral female identity.