THE GENETICS OF DOPA DECARBOXYLASE IN DROSOPHILA MELANOGASTER. II. ISOLATION AND CHARACTERIZATION OF DOPA-DECARBOXYLASE-DEFICIENT MUTANTS AND THEIR RELATIONSHIP TO THE α-METHYL-DOPA-HYPERSENSITIVE MUTANTS

Abstract

ABSTRACT Of 84 lethals isolated over the dopa decarboxylase (DDC) deficiency Df(2L)50, 8 have been identified as DDC-deficient alleles on the basis of their effect on DDC activity when heterozygous over the CyO balancer chromosome with activities ranging from 28% to 53% of controls. Some of the Ddc-deficient alleles exhibit intracistronic complementation. Most of the complementing pairs of alleles are much reduced in viability, e.g. < 5% of expected, and express a common syndrome of mutant phenes which can reasonably be inferred to derive from inadequately sclerotinized cuticle. Individuals heterozygous for the noncomplementing allele, Ddcn7, over the 12-band DDC deficiency, Df(2L)130, die at the end of embryogenesis as unhatched larvae with unpigmented mouth parts. The Ddc alleles and the l(2)amd α-methyl dopa (αMD) hypersensitive alleles are both located within the 11 band region 37B10-C7. The l(2)amd locus is immediately to the right of hk(2-53.9).Ddc has been mapped within 0.004 Map Units to the right of l(2)amd with a maximum estimated recombination frequency of 0.01%. None of the Ddc/CyO strains are sensitive to the dietary administration of α-methyl dopa (αMD), and complementation occurs between the Ddc deficient alleles and the l(2)amd alleles both on the basis of viability and DDC activity. No effect on DDC by the amd alleles has been found to date. Even in the complementing heterozygote, amdH1/amdH89, the level of activity, thermostability, and in vitro αMD inhibition of DDC remains unaffected. Although no biochemical phene has yet been established for the αMD hypersensitive amd alleles, it seems likely that the two groups of mutants are functionally related.