UAS regulatory sequences drive expression of a 2142bp cDNA sequence that extends from the vvl start codon to the second TAG stop codon. The first TAG stop codon in vvl has been mutated to a Lys codon; this results in a transgene that encodes solely the L isoform (this isoform is produced by the endogenous locus if translational stop codon readthrough of the first TAG codon occurs).