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Combining experimental evolution with whole‐genome resequencing is a promising new strategy for investigating the dynamics of evolutionary change. Published studies that have resequenced laboratory‐selected populations of sexual organisms have typically focused on populations sampled at the end of an evolution experiment. These studies have attempted to associate particular alleles with phenotypic change and attempted to distinguish between different theoretical models of adaptation. However, neither the population used to initiate the experiment nor multiple time points sampled during the evolutionary trajectory are generally available for examination. In this issue of Molecular Ecology, Orozco‐terWengel et al. (2012) take a significant step forward by estimating genome‐wide allele frequencies at the start, 15 generations into and at the end of a 37‐generation Drosophila experimental evolution study. The authors identify regions of the genome that have responded to laboratory selection and describe the temporal dynamics of allele frequency change. They identify two common trajectories for putatively adaptive alleles: alleles either gradually increase in frequency throughout the entire 37 generations or alleles plateau at a new frequency by generation 15. The identification of complex trajectories of alleles under selection contributes to a growing body of literature suggesting that simple models of adaptation, whereby beneficial alleles arise and increase in frequency unimpeded until they become fixed, may not adequately describe short‐term response to selection. 相似文献
3.
The Capricorn silvereye (Zosterops lateralis chlorocephalus) is ideally suited to investigating the genetic basis of body size evolution. We have isolated and characterized a set of microsatellite markers for this species. Seven out of 11 loci were polymorphic. The number of alleles detected ranged from two to five and observed heterozygosities between 0.12 and 0.67. One locus, ZL49, was found to be sex‐linked. This moderate level of diversity is consistent with that expected in an isolated, island population. 相似文献
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5.
Z Z Chen G P Schwartz L Zong G T Burke J D Chanley P G Katsoyannis 《Biochemistry》1988,27(16):6105-6111
A two-chain, disulfide linked, insulin-like compound embodying the A-domain of insulin-like growth factor I (IGF-I) and the B-chain of insulin has been synthesized and characterized with respect to insulin-like biological activity and growth-promoting potency. The compound displays a potency of ca. 41% relative to insulin in assays for insulin-like activity (e.g., lipogenesis) but significantly higher activity than insulin, ca. 730% relative to insulin, in growth factor assays (e.g., thymidine incorporation). The compound is, however, a less potent growth factor than IGF-I itself, ca. 26.5% relative to IGF-I, and is not recognized by IGF carrier proteins. We conclude that structural features contained in the A-domain of IGF-I are primarily responsible for the growth-promoting ability displayed by IGF-I, while features in the B-domain are responsible for recognition by IGF carrier proteins. 相似文献
6.
Repair of single nucleotide DNA mismatches transfected into mammalian cells can occur by short-patch excision 总被引:3,自引:0,他引:3
Synthetic DNA linkers containing a single mismatched nucleotide (C:A) are repaired without bias at high efficiency when introduced into mammalian cells on a SV40 shuttle vector. From the pattern of repair in vectors containing multiple linkers, it appears that DNA synthesis following mismatch excision can replace a length of DNA as short as 40 nucleotides. Furthermore, results from the introduction of linker molecules containing combinations of single-strand nicks suggest that transient unsealed nicks do not drive the direction of mismatch repair in mammalian cells, as has previously been proposed. 相似文献
7.
A T Smith S A Sanders R N Thorneley J F Burke R R Bray 《European journal of biochemistry》1992,207(2):507-519
A horseradish peroxidase variant ([F41V] HRP-C*), in which Val replaces the conserved Phe at position 41 adjacent to the distal His, has been constructed. Its composition and spectroscopic, catalytic and substrate-binding properties were compared with those of the wild-type recombinant (HRP-C*) and plant (HRP-C) enzymes. Presteady-state kinetic measurements of the rate constant for compound I formation (k1) revealed an eightfold decrease in the reactivity of the Phe41----Val variant towards H2O2, in comparison with HRP-C or HRP-C*. Measurement of the remaining rate constants, k2 and k3, for the two single-electron reduction reactions of [F41V] HRP-C with para-aminobenzoic acid as reducing substrate, showed that they were 2.5-fold and 1.3-fold faster, respectively. In contrast, analysis of data from steady-state assays with 2,2'-azinobis(3-ethylbenzthiazoline-6-sulphonate) as reducing substrate, showed decreased reactivity of the mutant enzyme to this compound, indicating a change in substrate specificity. Over the substrate range studied, the data for HRP-C* and for [F41V] HRP-C conformed to a simple modification of the accepted peroxidase mechanism in which a first-order step (ku), assumed to be product dissociation, becomes rate-limiting under our standard assay conditions. Calculations of rate constants from steady-state data yielded values of k1 for both enzyme forms in adequate agreement with those from pre-steady state measurements. They showed, furthermore, that both k3 for 2,2'-azinobis(3-ethylbenzthiazoline-6-sulphonate) and ku were substantially decreased, fivefold and tenfold, respectively, in the mutant. Analogous to the decrease in ku, we observed a twofold increase in the affinity of the mutant variant for the inhibitor benzhydroxamic acid. The coordination-state equilibrium of the haem iron also appeared shifted towards the hexacoordinate high-spin form. These observations indicate that in addition to affecting reactivity to H2O2, mutations in the distal region and close to the haem iron also affect reactivity towards different reducing substrates, inducing perturbations in the neighbourhood of the aromatic-substrate-binding site, known to be 0.8-1.2 nm from the haem iron. 相似文献
8.
Teratocarcinoma stem cells and early mouse embryos contain only a single major lamin polypeptide closely resembling lamin B 总被引:30,自引:0,他引:30
The nuclear lamina in adult mammalian somatic cells is composed of three major proteins, lamins A, B, and C. The expression of these proteins during the differentiation of teratocarcinomas and mouse embryogenesis is described. Embryos up to day 8 of gestation and embryonal carcinoma (EC) cells express only a single lamin species closely resembling, if not identical to, lamin B. Lamins A and/or C were detected in fertilized eggs, but disappear during the first 2-4 cleavage divisions, only reappearing in 8 day post-implantation embryos. These two lamins are absent from EC cells, but are strongly expressed in some of their derivatives. These results show that cells of the early mouse embryo do not have a functional requirement for lamins A and C and imply that the structural organization of the nucleus may change fundamentally during embryogenesis. 相似文献
9.
Structure and expression of the herpes simplex virus type 2 glycoprotein gB gene. 总被引:21,自引:17,他引:4
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L L Stuve S Brown-Shimer C Pachl R Najarian D Dina R L Burke 《Journal of virology》1987,61(2):326-335
The gene for glycoprotein gB2 of herpes simplex virus type 2 strain 333 was cloned, sequenced, and expressed in mammalian cells. The gB2 protein had an overall nucleotide and amino acid sequence homology of 86% with the cognate gB1 protein. However, of the 125 amino acid substitutions or deletions, only 12.5% were conservative replacements. These differences were clustered within an NH2-terminal region, a central region, and a COOH-terminal region, resulting in domains of near identity broken by small regions of marked divergence. Regions of greatest homology included a 90-amino-acid stretch starting at residue 484 and 39 amino acids spanning residues 835 to 873, which cover a rate-of-entry locus mapped to Ala-552 and a syn locus mapped to Arg-857, respectively, in gB1 by Bzik et al. (D. J. Bzik, B. A. Fox, N. A. DeLuca, and S. Person, Virology 133:301-314, 1984). Pellett et al. (P. E. Pellett, K. G. Kousoulas, L. Pereira, and B. Roizman, J. Virol. 53:243-253, 1985) mapped the mutations in three monoclonal antibody-resistant gB1 mutants between amino acids 273 and 443. These epitopes are included in a region of 98 residues identical between gB1 and gB2. The identity of this protein was verified by placing a truncated gene lacking the 303 carboxyl-terminal amino acids of gB2 into mammalian COS and CHO cells. Expression was demonstrated by immunofluorescence and radioimmunoprecipitation. This protein will be purified from the stable CHO cell lines and compared with gB1 for immunogenicity and protective efficacy in animal challenge models. 相似文献
10.
Purification and characterization of glutathione reductase from corn mesophyll chloroplasts 总被引:3,自引:0,他引:3
Differences in the apparent molecular weights of the subunits of glutathione reductase (EC 1.6.4.2) from pea chloroplasts and corn mesophyll chloroplasts have been recently reported. In order to more fully describe the differences between the enzymes from these two sources, glutathione reductase from the mesophyll chloroplasts of corn seedlings ( Zea mays L. cv. G-4507) has been purified 200-fold by affinity chromatography using adenosine 2',5'-disphosphate agarose. The purified enzyme had a specific activity of 26 μmol NADPH oxidized (mg protein)-1 min-1 . The native enzyme had a relative molecular weight of 190 ± 30 kDa and exhibited polypeptides of 65, 63, 34, and 32 kDa when separated on sodium dodecylsulfate-polyacrylamide gels. Comparisons of the results from electroblotting, native molecular weight and subunit molecular weight analyses suggest that the enzyme exists as a heterotetramer. Optimal enzyme activity was obtained at pH 8 in N-2-hydroxyethyl-piperazine-N'-2-ethanesulfonic acid (HEPES-NaOH) buffer. The sulfhydryl reagent, n -ethylmaleimide, inhibited enzymatic activity when incubated in the presence of NADPH while no inhibition was detected with oxidized glutathione in the incubation mixture. Reduced glutathione (5 m M ) inactivated the enzyme by 50%. This inactivation followed first order kinetics with a rate constant of 0.0028 s-1 . The enzyme was also inactivated by NADPH. The inactivation reached ca 90% within 30 min and followed first order kinetics with a rate constant of 0.0015 s-1 . 相似文献