Recombination between the two progenitor insertions has deleted the intervening sequence between them.
Scer\FRT-mediated recombination between the two progenitor insertions has deleted the sequence between them, removing rtp and part of Mms19 and CtsF.
Mms19+t5.6 rescues the homozygous lethality of the Df(3R)rtp1 chromosome.