Fig. 3. Rescue of the rn leg phenotype. (A-H) Adult male forelegs and (I) quantification of the number of tarsal segments. (A) Wild-type leg with sex comb (s.c.), 5 distinct tarsal segments (T1-5), and a claw at the tip of the 5th tarsus. (B) rn¹⁶/rn²⁰, a genetic null. The sex comb is completely missing in all cases and the five tarsi appear fused into one segment. Note, however, that the claw is still present. (C) rn^2–2/rn²⁰, which acts as a genetic null. (D) rn^GAL4#5/rn²⁰, a hypomorphic allelic combination. The sex comb is present and appears normal. The claw is normal. However, the tarsi are fused into two to three tarsal-like segments. (E) UAS-rn /+;rn^GAL4#5/+. UAS-rn causes no obvious disruption of the leg. (F) Rescue of rn mutants in UAS-rn /+;rn^GAL4#5/rn²⁰. The rn cDNA, expressed using the GAL4/UAS system, rescues the leg phenotype. (G) UAS-roe/+;rn^GAL4#5/+. UAS-roe has negative effects when expressed in the rn pattern. (H) UAS-roe/+;rn^GAL4#5/rn²⁰. UAS-roe is unable to rescue rn mutants. (I) Quantification of tarsi in wild type, rn mutants and rescue flies. The apparent number of tarsal segments was determined in rn mutants and rescue flies (>20 flies and >120 legs/genotype). The rescue is statistically significant to P<0.001 using a two-tailed t-test. Error bars represent the standard deviation. Temperature for rescue is 18°C though similar results were observed at 22°C (not shown).