110bp deletion that eliminates bases +9212 through +9321 relative to the transcription start site of the "maintenance" promoter, taking out both of the 3' splice sites of the male-specific Sxl exon, as well as the polypyrimidine tract that those splice sites depend on. Consequently, the fully female pre-mRNA Sxl splicing pattern occurs by default in this allele, regardless of X chromosome dose, and the gene is fully constitutive from the moment that the "establishment" promoter is active.