Heterogeneity of Lethals in a "Simple" Lethal Complementation Group

Of 24 ethyl methanesulphonate-induced, recessive-lethal mutations in the region 9E1-9F13 of the X chromosome of Drosophila melanogaster, eight fall into a typically homogeneous lethal complementation group associated with the raspberry (ras) locus. Mutations in this group have previously been shown to be pleiotropic, affecting not only ras but also two other genetic entities, gua 1 and pur 1, which yield auxotrophic mutations.--The eight new mutations have been characterized phenotypically in double heterozygotes with gua 1, pur 1 and ras mutations. Despite their homogeneity in lethal complementation tests, the mutations prove quite diverse. For example, two mutations have little or no effect on eye color in double heterozygotes with ras2. The differences between the lethals are allele-specific and cannot be explained as a trivial outcome of a hypomorphic series.--Taken alone, the lethal complementation studies mask the complexity of the locus and the diversity of its recessive lethal alleles. By extension, we argue that the general use of lethal saturation studies provides an unduly simplified image of genetic organization. We suggest that the reason why recessive lethal mutations rarely present complex complementation patterns is that complex loci tend to produce mutations that affect several subfunctions.     

Proceedings of the fifty-fourth Annual Meeting of the American Association of physical anthropologists to be held in Knoxville,Tennessee—Holiday Inn World's fair April 10–13, 1985

Empirical analyses and models of the lineal effects of fission indicate that considerable genetic differentiation may occur at the time of group formation, thus confusing the usual positive relationship between historical affiliation and genetic differentiation. We analyze the effects of fission pattern on variation in highly heritable morphological traits among eight social groups on Cayo Santiago. The analysis is performed using general network autocorrelation methods that quantitatively and directly measure the amount of variation in social group mean morphology that can be explained by fission. All of the fission autocorrelation coefficients are strongly negative, indicating that groups most recently formed by fission are most dissimilar. Also, most of the variation between groups can be explained by the fission pattern, indicating that lineal fission is the most important process generating between-group variation on Cayo Santiago.     

Amino acid sequence of an invertebrate FBP aldolase (from Drosophila melanogaster)

The complete amino acid sequence of FBP aldolase from Drosophila melanogaster has been determined. The enzyme contains four identical subunits of 360 amino acid residues. The primary structure of the monomer was established using automated Edman degradation on fragments prepared by CNBr-cleavage, by partial acid cleavage at the unique Asp-Pro bond and by oxidative cleavage at the three tryptophan residues. Manual Edman-Chang degradation was used on smaller peptides obtained by digestion with Staphylococcus aureus V8 protease, trypsin or chymotrypsin. The primary structure of Drosophila aldolase exhibits very extensive homology with the sequence of rabbit muscle aldolase (71% identity), thus explaining the early observation that Drosophila and mammalian aldolases form active interspecies hybrid quaternary structures (Brenner-Holzach, O. and Leuthardt, F., Eur. J. Biochem. (1972) 31, 423-426).     

Spin probe clustering in human erythrocyte ghosts

Summary A model has been developed for 5-nitroxide stearate, I(12,3), distribution in human erythrocyte ghosts which accurately predicts ESR spectral alterations observed with increased probe/total lipid (P/L) at 37°C. This spin probe occupies a class of high-affinity, noninteracting sites at low loading. Saturation occurs with increasing probe concentration, and, at higher loading, the probe inserts itself at initially dilute sites to form membranebound clusters of variable size. No low probe remains at high P/L where all I(12,3) clusters in a concentrated phase. This model allows determination of the dilute/clustered probe ratio, and shows that I(12,3) segregates in erythrocytes at what might otherwise be considered low P/L (e.g., 1/359). These findings validate the earlier use of empirical parameters to estimate probe sequestration in biological membranes.     

Transport of hydrophobic ions in erythrocyte membrane: I. Zero membrane potential properties

Summary The permeability and partition coefficients of tetraphenylarsonium (TPA) and several other organic cations were studied in the human erythrocyte using an ion-selective electrode. The permeability constant for the different cations could be explained quite well by differences in oil/water partition coefficients. No evidence for facilitated transport could be found. Binding of the organic ions occurred to both the cell membrane and to intracellular contents. Partitioning to the membrane remained relatively constant despite variation from ion intracellular binding with blood samples from different donors. TPA flux is stimulated by substoichiometric amounts of tetraphenylboron and other organic anions, suggesting an ion-pairing mechanism.     

Thigmomorphogenesis: The induction of callose formation and ethylene evolution by mechanical perturbation in bean stems

Mechanical perturbation by rubbing of the first internode of 11–12 day old plants of Phaseolus vulgaris L. cv. Cherokee wax induces the rapid deposition of callose in the cells of phloem and other tissues. Callose deposition begins immediately after mechanical perturbation, and shows a minor transient peak 1.5 h, and a major peak 6 h later. The callose gradually disappears and is gone after 3 days. If the stems are perturbed every day, the amount of callose decreases by day 2 but then gradually increases again through day 12. Both the top and bottom of the internode produce callose in response to mechanical perturbation. The evolution of ethylene in response to mechanical perturbation begins after 1 h, peaks at 2–3 h and is gone by 5–6 h. A spray of 10⁻² M 2-deoxy-D-glucose (DDG) completely blocks stem thickening, callose deposition and ethylene evolution due to mechanical perturbation. DDG at 10⁻⁵ to 10⁻⁴ M blocks callose production in mechanically perturbed stem segments and increases ethylene evolution from unperturbed stem segments to greater levels than those obtained by mechanically perturbed segments. It is concluded that mechanical perturbation of bean stems tissue induces deposition of callose more rapidly than it induces evolution of ethylene and that DDG can block both processes.     

Naphthofuranone phytoalexins from the grey mangrove, Avicennia marina

Infection of wound tissue of Avicennia marina seedlings by a fungus belonging to the genus Phytophthora induced the production of three chemically-related phytoalexins. After isolation by extraction, partition HPLC separation, one was identified as naphtho[1,2-b]furan-4,5-dione, and the other two tentatively as 3-hydroxynaphtho[1,2-b]furan-4,5-dione and 2-[2′-(2′-hydroxy)propyl]-naphtho[1,2-b]furan-4,5-dione.