ASYMMETRY - WHERE EVOLUTIONARY AND DEVELOPMENTAL GENETICS MEET

The mechanisms responsible for the fine tuning of development, where t he wild-type phenotype is reproduced with high fidelity, are not well understood. The difficulty in approaching this problem is the identifi cation of mutant phenotypes indicative of a defect in these fine-tunin g control mechanisms. Evolutionary biologists have used asymmetry as a measure of developmental homeostasis. The rationale for this was that , since the same genome controls the development of the left and right sides of a bilaterally symmetrical organism, departures from symmetry can be used to measure genetic or environmental perturbations. This p aper examines the relationship between asymmetry and resistance to org anophosphorous insecticides in the Australian sheep blowfly, Lucilia c uprina. A resistance gene, Rop-1, which encodes a carboxylesterase enz yme, also confers a significant increase in asymmetry. Continued expos ure of resistant populations to insecticide has selected a dominant su ppressor of the asymmetry phenotype. Genetic evidence indicates that t he modifier is the L. cuprina Notch homologue.