Delta and Serrate are redundant Notch ligands required for asymmetric cell divisions within the Drosophila sensory organ lineage.

Asymmetric divisions allow a precursor to produce four distinct cells of a Drosophila sensory organ lineage (SOL). Whereas this process requires cell-cell communication via Notch (N) receptor, mitotic recombination that removes the N ligand Delta (Dl) or Serrate (Ser) in the SOL had mild or no effect. Removal of both Dl and Ser, however, led to cell fate transformations similar to the N phenotype. Cell fate transformation occurred even when a single SOL cell lost both Dl and Ser. Thus, Dl and Ser are redundant in mediating signaling between daughter cells to specify their distinct cell fates.