Beta-alanine transaminase activity in black and suppressor of black mutations of Drosophila melanogaster.

An assay for beta-alanine transaminase activity in extracts of Drosophila melanogaster has been developed. By use of this assay, the levels of beta-alanine transaminase activity in several strains of flies has been examined as a function of developmental age. The black mutation shows elevated levels of activity compared to wild type, while suppressor of black strains show decreased levels compared to wild type.

Characterization of third chromosome dominant alpha-methyl dopa resistant mutants (Tcr) and their interactions with l(2)amd alpha-methyl dopa hypersensitive alleles in Drosophila melanogaster.

In Drosophila melanogaster two alleles at the Third chromosome resistance locus (Tcr; 3-39-6) were isolated in a screen of EMS mutagenized third chromosomes for dominant resistance to dietary alpha-methyl dopa, alpha-MD, a structural analogue of DOPA. Both alleles of Tcr are recessive lethals exhibiting partial complementation. Almost half (48.3%) of the Tcr40/Tcr45 heterozygotes die as embryos but some survive past adult eclosion. Both the embryonic lethal phenotype and the adult phenotype suggest that Tcr is involved in cuticle synthesis. Tcr mutants suppress the lethality of partially complementing alleles at the alpha-MD hypersensitive locus, l(2)amd. The viability of Tcr40/Tcr45, however, is not increased by the presence of a l(2)amd allele. The possibility that the Tcr and l(2)amd mutations reveal a catecholamine metabolic pathway involved in cuticle structure is discussed.

Intergenic suppression of the black mutation of Drosophila melanogaster.

Five X-linked, recessive alleles were isolated which suppressed both the pupal and adult coloration phenotypes of the black mutation. Electron micrographs of shed puparia revealed that the aberrant sclerotization of the black cuticle is also suppressed. Amino acid analysis indicated that suppression is associated with an increased concentration of beta-alanine, an amino acid known to be deficient in black. The suppressor locus mapped at the tip of the X, to the right of scute, and intragenic complementation was observed among the alleles.

The genetics of dopa decarboxylase in Drosophila melanogaster. I. Isolation and characterization of deficiencies that delete the dopa-decarboxylase-dosage-sensitive region and the alpha-methyl-dopa-hypersensitive locus.

A detailed cytogenetic investigation of 16 overlapping deficiencies in the 36C-40A region on the left arm of the second chromosome (2L) in Drosophila melanogaster is reported. These deficiencies permit a localization of both the dopa-decarboxylase-dosage-sensitive region and the alpha-methyl-dopa-hypersensitive locus, l(2) amd, to the same region, 37B10-37C7.

The genetics of dopa decarboxylase in Drosophila melanogaster. II. Isolation and characterization of dopa-decarboxylase-deficient mutants and their relationship to the alpha-methyl-dopa-hypersensitive mutants.

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 Cgamma-O 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. less than 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 alpha-methyl dopa (alphaMD) hypersensitive alleles are both located within the 11 band region 37B10-C7. The l(2) and locus is immediately to the right of hk(2-53.6). Ddc has been mapped within 0.004 Map Units to the right of l(2) and with a maximum estimated recombination frequency of 0.01%. None of the Ddc/CgammaOstrains are sensitive to the dietary administration of alpha-methyl dopa (alphaMD), 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 alphaMD inhibition of DDC remains unaffected. Although no biochemical phene has yet been established for the alphaMD hypersensitive amd alleles, it seems likely that the two groups of mutants are functionally related.