The DNA structures around the G6PD coding region in three high-G6PD activity mutants and their low-activity revertants of Drosophila melanogaster were analysed by Southern blot using a cloned G6PD gene as a probe. As a result, two kinds of insertion sequences were found; one was present just 5' to exon I (Insl), and the other within the intron (Ins2). The Insl sequence was 3-5 Kb in two mutants and 2-9 Kb in one mutant. In both cases, it consisted of a core sequence either 1-2 or 06 Kb long flanked by terminal repeats. On the other hand, low-activity revertants possessed either a defective Insl or no Insl. The Ins2 sequence was found in all mutants and revertants, but not in Canton S. Although a recombinant phage carrying the DNA fragment spanning the entire Insl has not been obtained, sequencing data of the clone containing only the terminal repeats demonstrated that the repeats are defective P elements. Comparison of the genomic DNA structures of mutants and revertants suggested that the element responsible for the positive regulation of the G6PD gene in the mutants would probably be the core sequence, but not the flanking defective P elements. It was also conjectured that the 1-2 Kb core sequence might be composed of two identical elements, which might transpose independently.

Two X-linked mutations that give rise to overproduction of glucose-6-phosphate dehydrogenase (G6PD) were found among the progenies of isogenic strains which had been subjected to selection for high G6PD activity. Mapping of the high-activity factor in these mutants was carried out using car ZwB sw males of low G6PD activity. As a result, the factor mapped 0.02-0.04 unit to the left of the Zw locus. The amount of the G6PD gene was also quantitated utilizing a cloned G6PD gene as a probe, but no significant difference was found between the mutants and low-G6PD activity flies which shared the same X, second, and third chromosomes with the mutants. These findings are consistent with our notion that the mutations might be regulatory mutations, possibly resulting from the insertion of a novel class of transposable genetic elements.

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A simple and rapid method is described for the determination of molybdenum() at mg･L -1 level based on differential pulse anodic stripping voltammetry at a glassy carbon disk electrode without adding any complexing agents. Octamolybdate formed in a 0.05 mol･L -1 hydrochloric acid -0.05 mol･L -1 nitric acid mixture solution (4 mL) at pH 3 in the presence of 10 vol acetone was electrodeposited on the working electrode at -1.2 V vs. SCE for 10 min, and the deposits were then stripped in another solution (the acid mixture solution in the absence of acetone) at a scan rate of 50 mV･s -1 to 0.2 V vs. SCE. A quantitative and reproducible peak was obtained, although the peak was split into two signals. The calibration (peak area vs. molybdenum() concentration) curve was linear over the concentration range of 1.0×10 -7 to 1.0×10 -6 mol･L -1 and passed through the origin, with a relative standard deviation of ca. 4 for 50 mg･L -1 (n＝5). The sensitivity was 8.9×10 -2 mA･V･(mg･L -1 ) -1 . The detection limit (3s) was 2.5×10 -8 mol･L -1 using a deposition time of 10 min. Tantalum(), tungsten(), vanadium() and phosphate interfered with the molybdenum() determination severely. The addition of hydrogen peroxide served to prevent interferences of titanium() and zirconium(). The proposed method was applied to the determination of 4.47 mass of molybdenum in the high-temperature alloy standard sample (JAERI-R4, Ni71.9 mass) and was achieved with fairly good precision and accuracy within 60 min without any preliminary separation of the matrix. The method could be applied to the determination of molybdenum of down to 20 mass ppm in nickel metal provided the deposition potential was changed into -0.9 V vs. SCE.