The P{lacW}tefk15914 insertion maps within the first exon of the tef gene, which itself is entirely contained within the first intron of fat-spondin. The processed mRNA of tef is wild type, despite the insertion being within the coding region (after nucleotide position 318 in the first exon).
Although the P{lacW}tefk15914 line was originally characterised as a lethal insertion, a viable line of flies homozygous for P{lacW}tefk15914 has been established.