fu1 heterozygotes carrying one copy of Su(fu)+ display a partially suppressed wing phenotype, the presence of P{SUFU000} recovers males with partially rescued fu wing phenotype (consistent with lack of Su(fu)+ function). fu41 heterozygotes carrying one copy of Su(fu)+ are pharate adult lethal and display a cos wing phenotype, the presence of P{SUFU000} recovers no males (consistent with lack of Su(fu)+ function).