Paper Chromatography of Pteridines of Prune and Clot Stocks of Drosophila Melanogaster.

HEN a stock of Drosophila melanogaster with chromosome 2 marked by wclot, cl, produced brown-eyed flies resembling clot but with the gene in the X chromosome, it was suspected that a translocation had occurred. However, genetic tests, including crosses to a newly acquired yellow prune stock ( y , p n ) showed that a mutation had occurred at the p n locus. The new allele, symbol pn591, is completely recessive to wild type, as are p n and c2, but in combination with clot produces a graded series of eye colors as follows: dark brown with genotypes pn59//pn591, cl/cl, and pnS93/Y, cl/cl; intermediate brown with genotypes p n a g ~ / p n a g l , c /+, and pna91/Y, cl /+; light brown with pns9i /pna9J , +/+ or +/+, cl/cl. Similar interactions were obtained from crosses using y p n and cl flies. Eye colors of living flies from stocks of pn , pna91, and cl are distinguishable. By the time the mutant origin of pns91 had been established, chromatographic studies were in progress and the emphasis had shifted to an analysis of biochemical differences among pn , the new allele pn591 and c2. Not only are there significant pteridine differences between clot and the “alleles0 at the prune locus, but also differences between p n and pna91. Among 30,617 F, flies from reciprocal P, crosses between p n and pna93 there were two with wild-type eye color, one male and one female. If p n and pn593 are recombinationally separate loci (pseudoalleles) and if flies carrying the cis arrangement are not identifiable the estimate of recombination is .013 percent. Examination of the “region” of prune in salivary chromosomes failed to show a doublet.