UASt regulatory sequences drive expression of a mutated form of Ser, in which five residues of the DSL domain have been mutated to alanines (amino acid replacements R251A, P252A, R253A, D254A and D255A).
Flies that express SerDSL.Scer\UAS under the control of Scer\GAL4ptc-559.1 are phenotypically wild type.