Rare Pseudoallelic Crossover between Two Phenotypically Identical Alleles at a Restricted Sublocus of Dumpy in Drosophila melanogaster

Abstract

THE dumpy locus has been extensively mapped^1–4. Many of the sites within the dumpy gene have phenotypic specificity ; that is, mutants of similar phenotypes map at the same restricted part of the region. A series of mutants which show an ov phenotype (oblique wings and thoracic vortices) were mapped to the right of lv¹ and to the left of v² (ref. 4). The ov mutants are viable as homozygotes and in combination with each other, except for ov^h, which is a facultative lethal in the homozygote but which is viable with the other ov alleles. The ov^h allele also shows a more extreme phenotype, and it is distinguishable in combination with other ov mutants by a more extreme phenotype. A crossover between ov¹ and ov^h was obtained by Southin⁵. The work reported here was carried out using other ov alleles of indistinguishable phenotype (ov¹ and ov^52b) in an attempt to establish critically the fine structure of the dumpy locus by obtaining crossovers between those alleles.