Showing papers by "Stephen J. O'Brien published in 1972"

The α-Glycerophosphate in DROSOPHILA MELANOGASTER II. Genetic Aspects

Abstract: Seven alleles of the α-Glycerophosphate dehydrogenase-1 (αGpdh-1) locus of Drosophila melanogaster have been described. These include two naturally occurring electrophoretic variants, one EMS-induced electrophoretic variant, and four EMS-induced "null" or "zero" mutants. With the electrophoretic variants, the locus was mapped to II-20.5 ± 2.5. A complementation matrix was prepared utilizing the null mutants. Three of the four mutants and a deletion of the locus (Grell 1967) exhibit dosage dependency. The dosage independent mutant exhibits complementation with two of the other null alleles. Flies genetically deficient in α-glycerophosphate dehydrogenase are fertile, but their relative viability is severely diminished. Such flies also lose the ability to sustain flight, an observation consistent with the enzyme's function in energy production. The levels of mitochondrial α-glycerophosphate oxidase, measured in flies genetically deficient in the cytoplasmic enzyme, were normal.

The α-glycerophosphate cycle in Drosophila melanogaster . I. Biochemical and developmental aspects

Abstract: The two α-glycerophosphate dehydrogenases ofDrosophila melanogaster (mitochondrial αGPO and soluble αGPDH) have been biochemically characterized in a preliminary investigation of the α-glycerophosphate cycle inDrosophila. The soluble enzyme is NAD linked and can be distinguished from the mitochondrial oxidase in terms of locational specificity,pH optimum, salt precipitation, and electrophoretic behavior. The mitochondrial enzyme is NAD independent and exhibits behavior typical of a lipoprotein. Extraction procedures are described for αGPO with nonionic detergents. Isoelectric focusing of αGPO on polyacrylamide gels resolved two molecular forms of αGPO which differ in isoelectric point, ease of extraction, and developmental and spatial distribution. Developmental profiles of both αGPO and αGPDH are presented. The occurrence of multiple forms of both the soluble (Wright and Shaw, 1969) and the mitochondrial forms of the enzymes is discussed in light of a multifunctional role of the α-glycerophosphate cycle inDrosophila.

The α-Glycerophosphate Cycle in Drosophila melanogaster. III. Relative Viability of "Null" Mutants at the α-Glycerophosphate Dehydrogenase-1 Locus

Abstract: The description of genetic variation in natural populations has involved three different general approaches: (1) the detection, by means of special genetic techniques, of genes in Drosophila which affect viability, fertility, or developmental rates (e.g., Dobzhansky and Spassky 1953) ; (2) the measurement of chromosomal inversion polymorphism in Drosophila (Dobzhansky 1970, chap. 5); and (3) the electrophoretic monitoring of gene-enzyme (allozyme) variation in a number of species from many different animal and plant phyla (e.g., Lewontin and Hubby 1966; O'Brien and MacIntyre 1969; Allard 1971; Prakash, Lewontin, and Hubby 1969; Selander and Yang 1969). The first approach uncovers cryptic variation with respect to various components of fitness; such variation is revealed by techniques that render chromosomes homozygous. The other two approaches reveal genetic variation virtually by direct observation. The relation of this variation to fitness is not at all immediately obvious; indeed, there are cogent arguments that much allozyme variation is selectively neutral (King and Jukes 1969; Kimura and Ohta 1971). The first method of measuring relative viability of wild chromosomes has provided a wealth of information to the field of population genetics mainly through the efforts of Dobzhansky and his colleagues (for references, see Dobzhansky 1970, p. 118; Wallace 1968, p. 36). Relative viability is determined through the use of invested balancer chromosomes which contain a dominant marker mutation and a recessive lethal. In these studies, male and female flies, heterozygous for the balancer chromosome and the same sampled chromosome, are mated to each other and their progeny are scored. The ratio of homozygous wild-type offspring to balancer heterozygous offspring has been determined for large numbers of wild chromosomes from natural populations of several Drosophila species. This ratio can be related to the ratio obtained by comparing the relative viability of heterozygotes for different wild chromosomes with that of the balancer heterozygotes in control cultures. It is striking that in the majority of analyses reported, regardless of which chromosome, population, or species is sampled, the frequency distribution of chromosome viability followed a uniquely distinct