Fig. 4. Genetic mapping of rib. (A) Map of deficiencies in the 55B-56D region and their lethal complementation behavior with rib (at least three rib alleles were tested). rib maps to the interval (*) between the left endpoint of Df(2R)GC8 (56B5) and the right endpoint of Df(2R)P34 (56C1). (B) Sequence polymorphism mapping of the left endpoint of Df(2R)GC8 and right endpoint of Df(2R)P34. Region deleted (–) or present (+) in Df(2R)GC8 or Df(2R)P34 chromosome as indicated by the absence (–) or presence (+) of a sequence polymorphism at that position (see Materials and Methods). Positions of some known and predicted genes (indicated by CG number) are shown. (C) Meiotic recombination mapping of rib¹ with respect to cora². cora⁺rib⁺ recombinant chromosomes (n=42) resulting from a crossover between cora² and rib¹ in a cora²,+/+,rib¹ transheterozygote were genotyped for five polymorphic markers (PM1-5) in the region. The percentages of recombinant chromosomes carrying the rib¹ chromosome allele of PM1, PM2 and PM3 are shown. None carried the rib¹ chromosome allele of PM4 or PM5, which map further to the right (not shown). This mapped rib¹ to the right of PM2 (dotted line at 28 kb), in an 9 kb interval (*) bounded by the right endpoint of Df(2R)P34 (dotted line at 37 kb). Extrapolation (broken line) places rib¹ in the CG7230 locus. Positions of transcripts in the region are shown. (D) Organization of CG7230 locus and cDNA. Boxes, exons; black, coding region; dotted line, right endpoint of Df(2R)P34; broken line, extrapolated position of rib¹ (from C); arrow, actual position of rib¹ mutation (see Fig. 5A).