The Mechanism of Position Effect—Experiments on the Phenotypic Expression of Position Effects in Relation to Changes in Pairing of Neighboring Chromosome Regions

Abstract

On the assumption that pairing conditions affect the manifestation of position effect, expts. were performed in which the eye-colors of flies (Drosophila melanogaster) carrying a white-mottled X-chromosome and either a normal unbroken X or one with a deficiency next to the w locus were compared. The eye-colors appear to be different. While these results can be regarded as supporting the hypothesis which the expts. were designed to test, it cannot be completely excluded at present that they are due to the action of modifiers, or to competition between alleles.