springer is inserted 5bp 5' to exon 7d. springer is flanked by a 4bp target site duplication. The element is orientated such that they contain a consensus polyadenylation signal, which includes the canonical AAUAAA element, and a GU rich domain within 50 nt 3' of the cleavage site.
The flight ability and myofibril phenotypes are fully rescued by one copy of Mhc+t41.9. Duplicated copy of Mhc present on Dp(2;3)osp3 is insufficient to rescue lethality due to the presence of a second site lethal mutation. Mhc+t41.9 can rescue lethality when the second site lethal is recombined off the chromosome.