Excision of the P{lacW} insertion and deletion of adjacent genomic DNA.
Homozygotes have partial joints at the boundary between tarsal segments 2 and 3 in 66% of cases (the joints are complete in the remaining 34% of cases).
fj4 has visible phenotype, enhanceable by d[+]/dachsnc104.6
fj4 has leg joint phenotype, enhanceable by d[+]/dachsnc104.6