THE GENETICS OF DOPA DECARBOXYLASE IN DROSOPHILA MELANOGASTER. 11. ISOLATION AND CHARACTERIZATION O F DOPA-DECARBOXYLASE-DEFICIENT MUTANTS AND THEIR RELATIONSHIP TO THE a-METHYL-DOPA-HYPERSENSITIVE MUTANTS THEODORE R. F. WRIGHT, GLENN C. BEWLEYZ

AND

ALLEN F. SHERALD3

Department of Biology, Uniuersity of Virginia, Charlottesuille, Virgin& 22901 Manuscript received December 5, 1975 Revised copy received May 25, 1976 ABSTRACT

Of 84 lethals isolated over the dopa decarboxylase (DDC) deficiency Df(2L.l.50, 8 have been identified as DDC-deficient alleles on the basis of their effect on DDC activity when heterozygous over the Cy0 balancer chromosome with activities ranging from 28% to 53% of cmtrols. 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 a-methyl dopa (aMD) 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 a-methyl dopa (aMD), 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, amdHl/amdH89, the level of activity, thermostability, and in vitro aMD inhibition of DDC remains unaffected. Although no biochemical phene has yet been established for the aMD hypersensitive amd alleles, it seems likely that the two groups of mutants are functionally related.




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DOPA-DECARBOXYLASE-DEFICIENT MUTANTS IN DROSOPHILA

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and Initially using b (48.5) and pr (54.5) as outside markers, SPARROW WRIGHT(1974) mapped each of six of the seven amd alleles on the basis of aMD hypersensitivity to a mean locus of 53.12 0.53 (the individual loci ranging from 52.0 to 53.5 for the six alleles). In addition, the HI allele was mapped on the basis of lethality to a locus between 53.1 and 54.0. The cytogenetic data and SHERALD 1976) presented in the preceding paper (WRIGHT,HODGETTS clearly places the amd locus closer to hk (53.9) rather than rdo (53) or I (2)Bld (53.1). In an attempt to localize precisely the amd locus relative to hk, pr/f amdH1cn bw 0 0 were crossed to Df(2L)I58, hk- cn bw/ rdo hk C y 0 8 8 or Df (2L)l30, hk- cn bw/CyO 8 8 and all Cy progenycounted. Non-Cy, non-hk progeny were testcrossed to rdo hk p r cn to identify the presence of rdo or pr in the non-Cy, non-hk chromosome and thereby determine whether amd is to the left or right of hk. Although 31,600 C y progeny were produced, only one 4pr +/Df(2L)I3OY hk- cn bw recombinant between amdH1and hk was recovered. These results indicate ihat the H I lesion in the amd locus is approximately .006 Map Units (2 x 1/31,600) to the right of hk. The maximum estimated recombination frequency is .03% equal to the upper limit of the 95% Poisson Confidence Interval (STEVENS 1942). Position of the Ddc and l(2)amd loci relative to each other: Since both the Ddc-deficient mutants and the aMD-hypersensitive amd locus are located within the eleven-band region 37B10-C7 delineated by Df(2L)lSO and Df(2L)E7I, it is of considerable interest to determine the distance between them. The crosses employed to answer these questions are given in Table 7. Since all non-Cy progeny were test-crossed to rdo hk pr o r rdo hk pr cn flies to score for the presence of pr, it was possible to determine that all the wild-type progeny recovered were either rdo hk nl pr/HI cn bw/DfI58, hk- cn bw triploid females or intersexes, genotypically matroclinous diploid (rdo hk nl pr/HI cn b w ) , or sterile, while none were pr +/DfI58, h k cn bw recombinants. (Since the appearance of these exceptional flies is clustered (Table 7), it is thought that some genetic factor (s) is (are) segregating in the heterozygous female parents which cause some of them to produce diploid eggs. It is possible that the matroclinous flies may arise from the fertilization of diploid eggs with the subsequent mitotic loss of the paternal complement of chromosomes.) In addition, even though the non-Cy, non-hk white-eyed 8 was sterile and therefore could not be test-crossed, its phenotype was unambiguous and is that expected for a conversion event in the amd locus. This means that no confirmed recombinants were recovered among an estimated 59,693 zygotes from Ddcnl/amdH1heterozygotes indicating that either the HI lesion and the nI lesion are less than 0.003 Map Units apart (2 x 1/59,693) with a maximum estimated recombination frequency of 0.01% equal to the upper limit of the 95% Poisson Confidence Interval (STEVENS 1942), or one of the mutant chromosomes significantly reduces recombination in the region. In order to test this latter possibility, a similar cross (Table 7) was set with the mutations amdHlaland Ddcn5,both of which exhibit intracistronic complementation. Among an estimated 55,265 zygotes one possible recombinant non-virgin

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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.

THE GENETICS OF DOPA DECARBOXYLASE IN DROSOPHILA MELANOGASTER. 11. ISOLATION AND CHARACTERIZATION O F DOPA-DECARBOXYLASE-DEFICIENT MUTANTS AND THEIR R...
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