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1.
A simple proof that certain quantities are independent of the geographical structure of population 总被引:3,自引:0,他引:3
T Maruyama 《Theoretical population biology》1974,5(2):148-154
This paper gives a proof that certain quantities are independent of the geographical structure of a population. The quantities are: (1) the fixation probability of a mutant; (2) the sum of the quantity x(1 ? x), where x is the mutant frequency, while the mutant is segregating; and (3) the quantity x(1 ? x) summed over the generations during which the gene frequency in the whole population assumes a specified value. The independence of geographical structure for the latter two quantities is not exact if there is selection, but is a close approximation.The model is a geographically structured version of Moran's haploid overlapping generation model. The population consists of colonies connected genetically by migration. Each individual has the same negative exponential lifetime distribution. When an individual dies, it is immediately replaced by an individual born in the same colony with a probability proportional to the frequency and fitness of the type giving birth. In a diploid population the quantity x(1 ? x) is proportional to the heterozygosity. 相似文献
2.
Gerardo Liljesthröm María Eugenia Brentassi Ana María Marino de Remes Lenicov 《Symbiosis (Philadelphia, Pa.)》2017,72(3):171-181
Delphacodes kuscheli establish mutualistic relationship with yeast-like symbionts (YLS) that live in the fat body and are necessary for host survival and reproduction. We estimated for a host of age t, its body weight, W(t), and the number of YLS per host, YLS(t). The host body weight was calculated as: W(t)?=?Lm/[1+ e (d–kt)], (Lm?=?the maximum observed weight, and d and k are constants), and the fat body was considered a fixed proportion of W(t). We calculated the number of YLS per unit host body mass: α(t)?=?YLS(t)/W(t). We also calculated the number of YLS per host, cYLS(t), and analyzed the pattern of variation in both sexes adapting the expression of the logistic model: cYLS(t)?=?KNoert/K+(ert -1)No, (No?=?initial number of YLS, r?=?intrinsic per capita rate of natural increase, and K?=?variable carrying capacity). In females the carrying capacity varied according to a constant proportion of the host’s weight: K(t)?=?αW(t). In males α(t) was considered a decreasing function of the host age: K(t)?=?α(t)W(t). The coefficients No, α, and r were subjected to parameterization. We found that the patterns of W(t) and YLS(t) of D. kuscheli were similar to other planthoppers. In females YLS increased up to the adult stage and then remained almost constant, varying similarly to individual weight. In males YLS increased up to the 5th instar nymph as the individual weight did, but the number of YLS decreased in the adult stage and the correlation was not so good. The calculated number of YLS per host matches reasonably well with the number estimated experimentally both in females and males. This is the first study that quantified and modeled the dynamics of YLS endosymbionts in a Neotropical planthopper pest. The models will be used in future studies for better understand the experimental reduction of YLS in young nymphal stages. 相似文献
3.
Roberto Pilu Andrea Bucci Laura Casella Chiara Lago Francesco Cerino Badone Elena Cassani Michela Landoni 《Molecular breeding : new strategies in plant improvement》2012,30(2):799-807
We produced and studied for 3?years two synthetic populations of maize differing in their constitution only for the selected alleles present at the red color 1 (r1) locus (R-sc vs. r?Cr). r1 is a regulatory gene conferring anthocyanin pigmentation in different tissues: the R-sc allele confers pigmentation only in the aleurone seed layer, while the r?Cr allele confers pigmentation in several tissues such as root, silk and anther but the seed is colourless. The colourless population (r?Cr/r?Cr) was characterized by improved agronomic features, such as ear weight and plant height, compared with the R-sc/R-sc coloured population. This finding was confirmed by studying single F4 R/r families where the presence of the r?Cr allele conferred positive features, acting as a dominant trait. Quantitative trait locus (QTL) analysis performed using molecular markers on the long arm of chromosome 10 (bin 10.06), where the r1 gene maps, identified a QTL map position for plant height tightly associated to the r1 gene. Thus the r1 gene may represent a major QTL or it could be closely linked to another gene involved in the agronomic performance of the two populations studied. 相似文献
4.
Yujiao Mao Jingjing Wei Qiang Zheng Na Xiao Qipei Li Yingnan Fu Yanan Wang Nianzhi Jiao 《Current microbiology》2012,65(5):568-574
A novel aerobic, bacteriochlorophyll-containing bacteria strain JLT1202rT was isolated from Beibu Gulf in the South China Sea. Cells were gram-negative, non-motile, and short-ovoid to rod-shaped with two narrower poles. Strain JLT1202rT formed circular, opaque, wine-red colonies, and grew optimally at 3–4?% NaCl, pH 7.5–8.0 and 28–30?°C. The strain was catalase, oxidase, ONPG, gelatin, and Voges–Proskauer test positive. In vivo absorption spectrum of bacteriochlorophyll a presented two peaks at 800 and 877?nm. The predominant cellular fatty acid was C18:1 ω7c and significant amounts of C16:0, C18:0, C10:0 3-OH, C16:0 2-OH, and 11-methyl C18:1 ω7c were present. Strain JLT1202rT contained Q-10 as the major respiratory quinone and the genomic DNA G+C content was 76.3?mol%. Phylogenetic analysis based on 16S rRNA gene sequences of various species with validly published names showed that strain JLT1202rT fell within the genus Roseibacterium, family Rhodobacteraceae, sharing the highest similarity with Roseibacterium elongatum OCh 323T (97.9?% similarity), followed by Dinoroseobacter shibae DFL 12T (95.4?% similarity). The phylogenetic distance of pufM genes between strain JLT1202rT and R. elongatum OCh 323T was 9.4?%, suggesting that strain JLT1202rT was distinct from the only strain of the genus Roseibacterium. Based on the variabilities of phylogenetic and phenotypic characteristics, strain JLT1202rT stands for a novel species of the genus Roseibacterium and the name R. beibuensis sp. nov. is proposed with JLT1202rT as the type strain (=JCM 18015T?=?CGMCC 1.10994T). 相似文献
5.
《Inorganica chimica acta》1988,142(1):69-74
The reaction of W2Cl4[P(n-Bu)3]4 with bis(diphenylphosphino)methane (dppm) affords the highly air-sensitive material, W2Cl4(dppm)2, which has been characterized by IR and visible spectroscopy, and by X-ray crystallography. The compound crystallizes in the centrosymmetric space group C2/c with the following parameters: a = 17.298(3); b = 17.011- (2); c = 18.413(2) Å; β = 98.93(2); V = 5352(2) Å3; Z = 4. The molecule is positioned about a C2 axis which allows for a net torsion angle of 17.25° down the WW vector. This does not seem to significantly effect the WW bond distance (2.269(1) Å) relative to other quadruply bonded ditungsten species. 相似文献
6.
Yu. N. Dnestrovskij S. V. Cherkasov A. Yu. Dnestrovskij S. E. Lysenko M. J. Walsh 《Plasma Physics Reports》2006,32(1):1-8
Models with critical gradients are widely used to describe energy balance in L-mode discharges. The so-called first critical gradient can be found from the canonical temperature profile. Here, it is suggested that discharge regimes with transport barriers can be described based on the idea of the second critical gradient. If, in a certain plasma region, the pressure gradient exceeds the second critical gradient, then the plasma bifurcates into a new state and a transport barrier forms in this region. This idea was implemented in a modified canonical profile transport model that makes it possible to describe the energy and particle balance in tokamak plasmas with arbitrary cross sections and aspect ratios. The magnitude of the second critical gradient was chosen by comparing the results calculated for several tokamak discharges with the experimental data. It is found that the second critical gradient is related to the magnetic shear s. The criterion of the transport barrier formation has the form (a 2/r)d/drln(p/p c ) > z 0 (r), where r is the radial coordinate, a is the plasma minor radius, p is the plasma pressure, p c is the canonical pressure profile, and the dimensionless function z O(r) = C O + C 1 s (with C 0i ~1, C 0e ~3, and C 1i,e ~2) describes the difference between the first and second critical gradients. Simulations show that this criterion is close to that obtained experimentally in JET. The model constructed here is used to simulate internal transport barriers in the JET, TFTR, DIII-D, and MAST tokamaks. The possible dependence of the second critical gradient on the plasma parameters is discussed. 相似文献
7.
Peter G. Smith 《生物化学与生物物理学报:生物膜》1975,375(1):124-129
At frequencies between 20 Hz and 1 kHz the impedance locus of the isolated frog skin is circular; below 20 Hz the resistive component of the impedance is frequently greater than would be expected from extrapolation of the high-frequency locus. At frequencies greater than twice the highest frequency at which there are deviations from the circular locus the variation of impedance Z with angular frequency ω is closely described by the equation Z = r1 + r0/[1+(jωτ)1-α], where j is √?1, r1 and r0 are resistance, τ is a time constant and α a constant in the range 0.02–0.14. 相似文献
8.
《Mathematical biosciences》1987,83(2):199-225
Unidirectional extraction of a substrate S in the capillaries following the arterial injection of a bolus containing S and a reference tracer R is assumed to follow first-order kinetics. If CR and CS denote normalized venous effluent concentrations of R and S, respectively, let L(t)=ln[CR(t)⧸CS(t)]. We derive a formula which expresses the experimental L(t) data in terms of the mean μ(t) and variance of the transit times of those capillaries which are contributing indicators at each sample time t. We examine the information thus contained in the L data about capillary and noncapillary transit times under several kinematic assumptions. We show that if the capillary and noncapillary transit times are stochastically independent with frequency functions hc(t) and hav(t), respectively, then the shapes of the graphs of L(t) and μ(t) depend on the variances and skewnesses of hc(t) and hav(t). Specifically, let r2 be the ratio of the variance of hc(t) to the variance of hav(t), and let r3 be the ratio of skewnesses in the same order. Then the graph of μ(t) is concave downward if r2⧸r3 > 1, concave upward if r2⧸r3< 1, and linear if r2⧸r3 = 1. If the fraction of S extracted is not too large, L(t) has nearly the same shape as μ(t), and therefore, L(t) contains information about hc(t) and hav(t). 相似文献
9.
Yuki Niwa Takehiro Suzuki Naoshi Dohmae Siro Simizu 《Molecular biology of the cell》2016,27(5):744-756
R-spondin1 (Rspo1) is a secreted protein that enhances Wnt signaling, which has crucial functions in embryonic development and several cancers. C-mannosylation is a rare type of glycosylation and might regulate secretion, protein–protein interactions, and enzymatic activity. Although human Rspo1 contains 2 predicted C-mannosylation sites, C-mannosylation of Rspo1 has not been reported, nor have its functional effects on this protein. In this study, we demonstrate by mass spectrometry that Rspo1 is C-mannosylated at W153 and W156. Using Lec15.2 cells, which lack dolichol-phosphate-mannose synthesis activity, and mutant Rspo1-expressing cells that replace W153 and W156 by alanine residues, we observed that C-mannosylation of Rspo1 is required for its secretion. Further, the enhancement of canonical Wnt signaling by Rspo1 is regulated by C-mannosylation. Recently DPY19 was reported to be a C-mannosyltransferase in Caenorhabditis elegans, but no C-mannosyltransferases have been identified in any other organism. In gain- and loss-of-function experiments, human DPY19L3 selectively modified Rspo1 at W156 but not W153 based on mass spectrometry. Moreover, knockdown of DPY19L3 inhibited the secretion of Rspo1. In conclusion, we identified DPY19L3 as the C-mannosyltransferase of Rspo1 at W156 and found that DPY19L3-mediated C-mannosylation of Rspo1 at W156 is required for its secretion. 相似文献
10.
Fujii T Yokoyama T Ninagi O Kakehashi K Obara Y Nenoi M Ishikawa T Mita K Shimada T Abe H 《Genetica》2007,130(3):267-280
In deletion-mapping of W-specific RAPD (W-RAPD) markers and putative female determinant gene (Fem), we used X-ray irradiation to break the translocation-carrying W chromosome (W
Ze
). We succeeded in obtaining a fragment of the W
Ze
chromosome designated as Ze
W, having 3 of 12 W-RAPD markers (W-Bonsai, W-Yukemuri-S, W-Yukemuri-L). Inheritance of the Ze
W fragment by males indicates that it does not include the Fem gene. On the basis of these results, we determined the relative positions of W-Yukemuri-S and W-Yukemuri-L, and we narrowed
down the region where Fem gene is located. In addition to the Ze
W fragment, the Z chromosome was also broken into a large fragment (Z1) having the +
sch
(1-21.5) and a small fragment (Z2) having the +
od
(1-49.6). Moreover, a new chromosomal fragment (Ze
WZ2) was generated by a fusion event between the Ze
W and the Z2 fragments. We analyzed the genetic behavior of the Z1 fragment and the Ze
WZ2 fragment during male (Z/Z1
Ze
WZ2) and female (Z1
Ze
WZ2/W) meiosis using phenotypic markers. It was observed that the Z1 fragment and the Z or the W chromosomes separate without fail. On the other hand, non-disjunction between the Ze
WZ2 fragment and the Z chromosome and also between the Ze
WZ2 fragment and the W chromosome occurred. Furthermore, the females (2A: Z/Ze
WZ2/W) and males (2A: Z/Z1) resulting from non-disjunction between the Ze
WZ2 fragment and the W chromosome had phenotypic defects: namely, females exhibited abnormal oogenesis and males were flapless
due to abnormal indirect flight muscle structure. These results suggest that Z2 region of the Z chromosome contains dose-sensitive gene(s), which are involved in oogenesis and indirect flight muscle development. 相似文献
11.
Kleinschmidt JH Bulieris PV Qu J Dogterom M den Blaauwen T 《Journal of molecular biology》2011,407(2):316-1693
We present a detailed study on the formation of neighboring β-strands during the folding of a monomeric integral membrane protein of the β-barrel type. β-Strand and β-barrel formations were investigated for the eight-stranded transmembrane domain of outer membrane protein A (OmpA) with single-tryptophan (W), single-cysteine (C) OmpA mutants. Based on the OmpA structure, W and C were introduced in two neighboring β-strands oriented toward the hydrocarbon core of the membrane. Replaced residue pairs were closer to either the periplasmic turns (named cis-side) or the outer loops (named trans-side) of the strand. WnCm OmpA mutants containing W at position n and C at position m along the polypeptide chain were labeled at the C by a nitroxyl spin label, which is a short-range fluorescence quencher. To monitor the association of neighboring β-strands, we determined the proximity between fluorescent W and labeled C in OmpA folding experiments by intramolecular fluorescence quenching. Formation of native β-strand contacts in folding experiments required the lipid membrane. Residues in the trans-side of strands β1, β2, and β3, represented by mutants W15C35 (β1β2, trans) and W57C35 (β3β2, trans), reached close proximity prior to residues in the N(β1)- and C(β8)-terminal strands as examined for mutants W15C162 (β1β8, trans) and W7C170 (β1β8, cis). Tryptophan and cysteine converged slightly faster in W15C162 (β1β8, trans) than in W7C170 (β1β8, cis). The last folding step was observed for residues at the cis-ends of strands β1 and β2 for the mutant W7C43 (β1β2, cis). The data also demonstrate that the neighboring β-strands associate upon insertion into the hydrophobic core of the lipid bilayer. 相似文献
12.
Christoph Kuhn 《Journal of biological physics》2005,31(3-4):587-597
A simple theoretical model of a Darwinian system (a periodic system with a multiplication phase and a selection phase) of
entities (initial form of polymer strand, primary mutant and satellite mutants) is given.
First case: one mutant is considered. One individual of the mutant appears in the multiplication phase of the first generation.
The probabilities to find N mutants WnM(N) after the multiplication phase M of the n-th generation (with probability δ of an error in the replication, where all possible errors are fatal errors) and WnS(N) after the following selection phase S (with probability β that one individual survives) are given iteratively. The evolutionary
tree is evaluated. Averages from the distributions and the probability of extinction W∞S(0) are obtained.
Second case: two mutants are considered (primary mutant and new form). One individual of the primary mutant appears in the
multiplication phase of the first generation. The probabilities to find Np primary mutants and Nm of the new form WnM(Np, Nm) after the multiplication phase M of the n-th generation (probability ε of an error in the replication of the primary mutant giving the new form) and WnS(Np, Nm) after the following selection phase S (probabilities βp and βm that one individual each of the primary mutant and of the new form survives) are given iteratively. Again the evolutionary
tree is evaluated. Averages from the distributions are obtained. 相似文献
13.
Diploid wild-type cells of Saccharomyces and cells homozygous for one of the single genes rs1, rs2 of the two alleles of the rs3 gene (rad 2 gene) were tested for their response to ionizing irradiation in the presence and absence of oxygen. Both immediate and delayed plating (agar-holding) techniques were used.An identical oxygen enhancement ratio (OER) of 2.5 was observed in rs1rs1, rs2rs2 cells and the wild type. In rs3?1rs3?1 and rs3?2rs3?2 cells the OER was reduced. Their sensitivity to ionizing irradiation in oxic conditions was the same as that of the wild type.rs2rs2 cells showed an increase in relative sensitivity by a factor of 4 in both conditions of irradiation. The relative sensitivity of rs1rs1 cells was increased by a factor of 2.5 in hypoxic conditions and the sensitivity in hypoxia was identical to that of wild type cells in oxic conditions. In contrast to haploid rs1 cells the oxygen effect was fully expressed in diploid rs1rs1 cells.The results on diploid strains are discussed in terms of three independent genetically determined repair systems in Saccharomyces. The expression of these systems is influenced by ploidy. 相似文献
14.
Genic variation in male haploids and male diploids was compared assuming constant fitnesses (derived from computer-generated random numbers) and infinite population size. Several models were studied, differing by the fitness correlation between the sexes (rs) and genotypes (rg), and by the intensity of selection as measured by the coefficient of variation (CV) of the fitness distribution. Genic variation was quantified using the proportion of polymorphic loci, P, the gene diversity at polymorphic loci, Hp, and the gene diversity over all loci, Ha. The two genetic systems were compared via variation ratios: variation in male haploidy/variation in male diploidy.—P and Ha were markedly lower for male-haploids than for male diploids, the variation ratios declining with increasing rs, rg and CV, but the two genetic systems were similar for Hp. Except for male diploids with rs = 1, the two sexes had different equilibrium gene frequencies but the sample sizes required to detect such differences reliably were larger than usually possible in surveys of natural populations.—Data from natural populations fit the above trends qualitatively, but the variation ratios are much lower than those from our analyses, except that for Hp, which is higher when Drosophila is excluded. Also, the frequency distribution of most common alleles from electrophoretic data has a deficiency of intermediate frequencies compared to that from the computer-generated sets of fitnesses, possibly reflecting either the influence of stochastic processes shifting frequencies away from equilibrium or the involvement of alleles under selection-mutation balance.——While electrophoretic data suggest that Drosophila has unusually high levels of genic variation, unusually low levels of genic variation in male haploids compared with male diploids are not strongly indicated. However, if further data confirm male haploids as having low levels of genic variation, likely explanations are that the bulk of electrophoretically detected variation involves fixed-fitness balancing selection, selection-mutation balance involving slightly deleterious recessive alleles, new favorable male haploid alleles moving more rapidly to fixation than under male diploidy and thus carrying linked loci to fixation faster, or some combination of these possible factors. 相似文献
15.
The entropy H(po,p*) of a population with the initial allele frequency po given the equilibrium polymorphic frequency p* has been proposed as a measure of natural selection. In the present paper, we have extended this concept to include a particular aspect of density-dependent selection. We compared size trajectory of a population initially at genetic equilibrium, N(t), with the size trajectories of populations not initially at p*,N(t), but which do eventually converge to a common equilibrium allele frequency and equilibrium density, N*. The following experimentally testable hyopthesis was established. The total area defined by the difference between the trajectories of N(t) and N(t) as they converge to N* is directly proportional to the fitness entropy when population size is transformed using the density-dependent fitness value. Two properties of this relationship were noted. First, it is independent of the magnitude of natural selection and, secondly, it does not depend upon the initial population density as long as the equilibrium and nonequilibrium populations have the same initial numbers. This hypothesis was evaluated with experimental data on the flour beetle Tribolium castaneum. 相似文献
16.
Photorespiration in Green Plants During Photosynthesis Estimated by Use of Isotopic CO(2) 总被引:5,自引:5,他引:0
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Photosynthetic re-absorption of photorespired CO2 causes underestimation in measured photorespiration and turnover rate of the substrate for photorespiration. Actual values of photorespiration exceed the measured by a factor greater than 1 + R′w/rp + [CL]x/(rp·Lx). (R′w and rp are the partial resistances to CO2 uptake between atmosphere, mesophyll evaporating surface, and photosynthetic sink, respectively; Lx is the measured flux of photorespired CO2 and [CL]x is the ambient conc of photorespired CO2). In 8 species, 1 + R′w/rp alone amounted to a correction ranging between 148% and 233%. 相似文献
17.
Background
Microarray analysis is a powerful technique for investigating changes in gene expression. Currently, results (r-values) are interpreted empirically as either unchanged or up- or down-regulated. We now present a mathematical framework, which relates r-values to the macromolecular properties of population-average cells. The theory is illustrated by the analysis of published data for two species; namely, Mycobacterium bovis BCG Pasteur and Mycobacterium smegmatis mc2 155. Each species was grown in a chemostat at two different growth rates. Application of the theory reveals the growth rate dependent changes in the mycobacterial proteomes.Principal Findings
The r-value r (i) of any ORF (ORF(i)) encoding protein p (i) was shown to be equal to the ratio of the concentrations of p (i) and so directly proportional to the ratio of the numbers of copies of p (i) per population-average cells of the two cultures. The proportionality constant can be obtained from the ratios DNA: RNA: protein. Several subgroups of ORFs were identified because they shared a particular r-value. Histograms of the number of ORFs versus the expression ratio were simulated by combining the particular r-values of several subgroups of ORFs. The largest subgroup was ORF(j) (r (j) = 1.00± SD) which was estimated to comprise respectively 59% and 49% of ORFs of M. bovis BCG Pasteur and M. smegmatis mc2 155. The standard deviations reflect the properties of the cDNA preparations investigated.Significance
The analysis provided a quantitative view of growth rate dependent changes in the proteomes of the mycobacteria studied. The majority of the ORFs were found to be constitutively expressed. In contrast, the protein compositions of the outer permeability barriers and cytoplasmic membranes were found to be dependent on growth rate; thus illustrating the response of bacteria to their environment. The theoretical approach applies to any cultivatable bacterium under a wide range of growth conditions. 相似文献18.
19.
Distribution of Gene Frequency as a Test of the Theory of the Selective Neutrality of Polymorphisms 总被引:44,自引:10,他引:34
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The variation in gene frequency among populations or between generations within a population is a result of breeding structure and selection. But breeding structure should affect all loci and alleles in the same way. If there is significant heterogeneity between loci in their apparent inbreeding coefficients F=sp2/p(1-p), this heterogeneity may be taken as evidence for selection. We have given the statistical properties of F and shown how tests of heterogeneity can be made. Using data from human populations we have shown highly significant heterogeneity in F values for human polymorphic genes over the world, thus demonstrating that a significant fraction of human polymorphisms owe their current gene frequencies to the action of natural selection. We have also applied the method to temporal variation within a population for data on Dacus oleae and have found no significant evidence of selection. 相似文献
20.
Charles J. Mode 《Bulletin of mathematical biology》1972,34(1):13-31
A bisexual multiple branching process is studied. Consider a population with respect to three genotypes in both the female and male populations and let $$X(n) = \left\langle {X_1 (n), X_2 (n), X_3 (n)} \right\rangle and Y(n) = \left\langle {Y_1 (n), Y_2 (n), Y_3 (n)} \right\rangle$$ be random vectors giving the number of females and males (respectively) of each genotype in generationn. The mating of females and males is accommodated in the model withZ ij (n) representing the number of females of theith genotype mated with a male of thejth genotype in generationn. The mating system is such that a female may be mated to only one male but a male may be mated with more than one female. By arranging the nine random variablesZ ij (n),i, j=1, 2, 3, in a 1×9, vectorZ(n) it is shown that under certain conditions there is a positive constant ? such that when ?>1 the vectorsZ n /ρn,X n /ρn andY n /ρn converge almost surely asn→∞ to random vectors with fixed directions. The paper is divided into four sections. In section 1 the model is described in detail and its potential applications to population genetics are discussed. In section 2, the generating function of the transition probabilities of theZ-process are derived. Section3 is devoted to the study of the limiting behavior of the first and second moments of theZ-process, and in section4 the results of section3 are utilized to study the behavior of the random vectorsZ(n),X(n) andY(n) asn→∞. 相似文献