Construction of an Unstable Ring-X Chromosome Bearing the Autosomal Dopa Decarboxylase Gene in Drosophila melanogaster and Analysis of Ddc Mosaics

Donald A. Gailey ¹, Deborah L. Bordne ¹, Ana Maria Vallés ¹, Jeffrey C. Hall ¹, and Kalpana White ¹

¹ Department of Biology, Brandeis University, Waltham, Massachusetts 02254

An unstable Ring-X chromosome, Ddc⁺- Ring-X carrying a cloned Dopa decarboxylase (Ddc) encoding segment was constructed. The construction involved a double recombination event between the unstable Ring-X, R(1)w^vC and a Rod-X chromosome which contained a P-element mediated Ddc ⁺ insert. The resulting Ddc⁺-Ring-X chromosome behaves similarly to the parent chromosome with respect to somatic instability. The Ddc⁺-Ring-X chromosome was used to generate Ddc mosaics. Analyses of Ddc mosaics revealed that while there was no absolute requirement for the Ddc ⁺ expression in either the epidermis or the nervous system, very large mutant clones did affect the viability of the mosaic.