Consanguineous marriages in Italy: A Note

Abstract

A general multifactorial model is given for the inheritance of traits that exhibit a sexual dimorphism. The model allows for polygenic inheritance, cultural transmission, phenotypic assortative mating, and a common environment of rearing. Several cultural mechanisms are described for which transmission from parent to offspring is sex‐dependent and for which many different patterns of sex‐specific correlations can result. A special case of the general model is described in which phenotypic differences between males and females are due only to differences in nontransmissible environmental factors and/or genetic factors that do not contribute to variability within a sex. Application of these models to human spatial visualizing ability, using data reported by others, gives an estimate of 45 per cent for the proportion of the variance that is accounted for by transmissible factors. Neither an X‐linked hypothesis nor a sex‐specific cultural mechanism is required to explain the transmission of spatial ability.     

Resolution of genetic and cultural inheritance in twin families by path analysis: application to HDL-cholesterol.

A path model and associated statistical method for the analysis of data on twin families are introduced and applied to high density lipoprotein cholesterol (HDL-c) observations in the Swedish Twin Family Study. The proposed path model incorporates both genetic and environmental sources of familial resemblance, maternal environmental effects, intergenerational differences in heritabilities, marital resemblance due to either primary or secondary phenotypic homogamy, and twin residual environmental correlations. Application of the model to HDL-c levels resulted in parameter estimates consistent with those reported in earlier reviews and in the analysis of nuclear family and twin data. Genetic heritability was estimated as h2 = .363 +/- .243, cultural heritability as c2 = .187 +/- .082, and the proportion of phenotypic variance due to residual environmental effects as r2 = .450 +/- .207. Although the parameter estimates were comparable, the statistical tests of hypotheses were, relative to other designs, of low statistical power. It appears that environmental indices are necessary for powerful tests of hypotheses.     

Metal binding ability of hypermodified nucleosides of t-RNA. Potentiometric and spectroscopic studies on the metal complexes of N-[(9-β-D-ribofuranosylpurin-6-yl)carbamoyl] threonine

Copper(II), nickel(II), zinc(II), manganese(II), and magnesium(II) complexes of t⁶A (N-[9-β-D-ribofuranosylpurin-6-yl)carbamoyl] threonine and t⁶Ade (N⁶(threoninocarbonyl)adenine) were studied by potentiometric and spectroscopic methods. It was found that t⁶Ade has three dissociable protons in the accessible pH range (N¹ and N⁹ of purine and carboxylate), while only two pK values are characteristic of t⁶A. Magnesium(II) and manganese(II) do not interact effectively with these ligands, but copper(II) and nickel(II) ions form very stable complexes with the coordination of purine N¹, deprotonated amide nitrogen, and carboxy late oxygen donors.     

Familial Clustering of Abdominal Visceral Fat and Total Fat Mass: The Québec Family Study

The evidence for common familial factors underlying total fat mass (estimated from underwater weighing) and abdominal visceral fat (assessed from CT scan) was examined in families participating in phase 2 of the Québec Family Study (QFS) using a bivariate familial correlation model. Previous QFS investigations suggest that both genetic (major and polygenic) and familial environmental factors influence each phenotype, accounting for between 55% to 71% of the phenotypic variance in fat mass, and between 55% to 72% for abdominal visceral fat The current study suggests that the bivariate familial effect ranges from 29% to 50%. This pattern suggests that there may be common familial determinants for abdominal visceral fat and total fat mass, as well as additional familial factors which are specific to each. The relatively high spouse cross-trait correlations usually suggest that a large percent of the bivariate familial effect may be environmental in origin. However, if mating is not random, then the spouse resemblance may reflect either genetic or environmental causes, depending on the source [i.e., through similar genes or cohabitation (environmental) effects]. Finally, there are significant sex differences in the magnitude of the familial cross-trait correlations involving parents, but not offspring, suggesting complex generation (i.e., age) and sex effects. For example, genes may turn on or off as a function of age and sex, and/or there may be an accumulation over time of effects due to the environment which may vary by sex. Whether the common familial factors are genetic (major and/or polygenic), environmental, or some combination of both, and whether the familial expression depends on sex and/or age warrants further investigation using more complex models.     

闽江口海蜇渔业生态学研究

根据1993年5～9月的调查材料,研究了福建闽江口海域海蜇的渔业生态学。其密度和生物量高峰分别出现在6月20日和7月10日;群体伞径范围为18～546mm,平均328.8mm.体重范围为0.5～9540g,平均2877.4g;伞径为345～485mm的雌性有性繁殖力在1120.6×10⁴～3754.8×10⁴粒,平均2444.7×10⁴粒,有性生殖期在8月初至11月;采用高次方程和指数高次方程分别模拟伞径和体重生长,生长方程为:Φ_t=12.1337+17.7048t+3.1385t²-0.2049t³+0.00302t⁴,log_eW_t=-0.5749+1.4818t-0.0771t²+0.00129t³;以生物经济学原理确定7月20日为合理开捕期,开捕伞径为465.8mm.讨论分析了执行合理开捕期和开捕规格,对保护和合理利用海蜇资源,提高经济效益的重要意义.     

Genes and environment

Many quantitative characters depend on the action of a large number of genes and environmental factors. The mode of inheritance of these characters is polygenic. The phenotypic variance of the character is the sum of the components, thus the genetic and the environmental variances (VP = VG + VE). The degree of genetic determination VG/VP and VE/VP are difficult to estimate in man. The heritability a related coefficient to VG/VP can be estimated from the degree of ressemblance between relatives. The heritability is the additive genetique variance as a proportion of the phenotypic variance. Polygenic threshold inheritance can account for the familial non mendelian distribution of multifactorial diseases.     

Age and sex affect quantitative genetic parameters for dominance rank and aggression in free‐living greylag geese

Knowledge of the genetic and environmental influences on a character is pivotal for understanding evolutionary changes in quantitative traits in natural populations. Dominance and aggression are ubiquitous traits that are selectively advantageous in many animal societies and have the potential to impact the evolutionary trajectory of animal populations. Here we provide age‐ and sex‐specific estimates of additive genetic and environmental components of variance for dominance rank and aggression rate in a free‐living, human‐habituated bird population subject to natural selection. We use a long‐term data set on individually marked greylag geese (Anser anser) and show that phenotypic variation in dominance‐related behaviours contains significant additive genetic variance, parental effects and permanent environment effects. The relative importance of these variance components varied between age and sex classes, whereby the most pronounced differences concerned nongenetic components. In particular, parental effects were larger in juveniles of both sexes than in adults. In paired adults, the partner's identity had a larger influence on male dominance rank and aggression rate than in females. In sex‐ and age‐specific estimates, heritabilities did not differ significantly between age and sex classes. Adult dominance rank was only weakly genetically correlated between the sexes, leading to considerably higher heritabilities in sex‐specific estimates than across sexes. We discuss these patterns in relation to selection acting on dominance rank and aggression in different life history stages and sexes and suggest that different adaptive optima could be a mechanism for maintaining genetic variation in dominance‐related traits in free‐living animal populations.     

Competition can maintain genetic but not environmental variance in the presence of stabilizing selection

A population in which there is stabilizing selection acting on quantitative traits toward an intermediate optimum becomes monomorphic in the absence of mutation. Further, genotypes that show least environmental variation are also favored, such that selection is likely to reduce both genetic and environmental components of phenotypic variance. In contrast, intraspecific competition for resources is more severe between phenotypically similar individuals, such that those deviating from prevailing phenotypes have a selective advantage. It has been shown previously that polymorphism and phenotypic variance can be maintained if competition between individuals is "effectively" stronger than stabilizing selection. Environmental variance is generally observed in quantitative traits, so mechanisms to explain its maintenance are sought, but the impact of competition on its magnitude has not previously been studied. Here we assume that a quantitative trait is subject to selection for an optimal value and to selection due to competition. Further, we assume that both the mean and variance of the phenotypic value depend on genotype, such that both may be affected by selection. Theoretical analysis and numerical simulations reveal that environmental variance can be maintained only when the genetic variance (in mean phenotypic value) is constrained to a very low level. Environmental variance will be replaced entirely by genotypic variance if a range of genotypes that vary widely in mean phenotype are present or become so by mutation. The distribution of mean phenotypic values is discrete when competition is strong relative to stabilizing selection; but more genotypes segregate and the distribution can approach continuity as competition becomes extremely strong. If the magnitude of the environmental variance is not under genetic control, there is a complementary relationship between the levels of environmental and genetic variance such that the level of phenotypic variance is little affected.     

Genetic and environmental influences on self-reported and parent-reported behavior problems in young adult adoptees

The aim of the present study was to estimate the genetic, shared and nonshared environmental contributions to self-reported and parent-reported internalizing and externalizing problems in a follow-up study of intercountry adopted young adults. Young Adult Self-Report ratings were obtained from 1475 adoptees aged 22–32 years and Young Adult Behavior Checklist ratings from 1115 adoptive parents. For the genetic analyses, a subset of 143 adopted biologically related and 295 unrelated siblings was used. The data were subjected to model fitting decomposing three sources of variance: genetic factors (A) shared environment (C) and nonshared environment (E). Genetic factors were of more importance in both self-reported ( A ²= 54%, C ²= 0, and E ²= 46%) and parent-reported ( A ²= 76%, C ²= 15% and E ²= 9%) internalizing problems. Environmental factors were of more importance in both self-reported ( A ²= 33%, C ²= 17% and E ²= 50%) and parent-reported ( A ²= 28%, C ²= 27% and E ²= 45%) externalizing problems. This was in contrast with findings from the first and second assessments in the same sample during adolescence when genetic factors were more important in explaining externalizing problems compared with internalizing problems. Our results suggest a developmental reversal in genetic and environmental influences on behavior problems from early adolescence into adulthood, which could be related to different underlying developmental trajectories.     

Natural selection on the genetical component of variance in body condition in a wild bird population

Although there is substantial evidence that skeletal measures of body size are heritable in wild animal populations, it is frequently assumed that the nonskeletal component of body weight (or ‘condition’) is determined primarily by environmental factors, in particular nutritional state. We tested this assumption by quantifying the genetic and environmental components of variance in fledgling body condition index (=relative body weight) in a natural population of collared flycatchers (Ficedula albicollis), and compared the strength of natural selection on individual breeding values with that on phenotypic values. A mixed model analysis of the components of variance, based on an ‘animal model’ and using 18 years of data on 17 717 nestlings, revealed a significant additive genetic component of variance in body condition, which corresponded to a narrow sense heritability (h²) of 0.30 (SE=0.03). Nongenetic contributions to variation in body condition were large, but there was no evidence of dominance variance nor of contributions from early maternal or common environment effects (pre‐manipulation environment) in condition at fledging. Comparison of pre‐ and post‐selection samples revealed virtually identical h² of body condition index, despite the fact that there was a significant decrease (35%) in the levels of additive genetic variance from fledging to breeding. The similar h² in the two samples occurred because the environmental component of variance was also reduced by selection, suggesting that natural selection was acting on both genotypic and environmental variation. The effects of selection on genetic variance were confirmed by calculation of the selection differentials for both phenotypic values and best linear unbiased predictor (BLUP) estimates of breeding values: there was positive directional selection on condition index both at the phenotypic and the genotypic level. The significant h² of body condition index is consistent with data from human and rodent populations showing significant additive genetic variance in relative body mass and adiposity, but contrasts with the common assumption in ecology that body condition reflects an individual’s nongenetic nutritional state. Furthermore, the substantial reduction in the additive genetic component of variance in body condition index suggests that selection on environmental deviations cannot alone explain the maintenance of additive genetic variation in heritable traits, but that other mechanisms are needed to explain the moderate to high heritabilities of traits under consistent and strong directional selection.     

β-甘露聚糖酶末端残基变体对其酶学特性的影响

本研究用宇佐美曲霉Aspergillus usamii的5家族β-甘露聚糖酶AuMan5A为母本,借助同源建模、分子对接及分子动力学模拟等理性设计方法,将AuMan5A的N-末端和C-末端分别截去3个无规则的氨基酸残基,构建出截短的β-甘露聚糖酶 AuMan5A^N3C3.将AuMan5A和AuMan5A^N3C3的编码基因分别在毕赤酵母GS115中进行表达,对表达产物进行了初步纯化并分析比较了其酶学特性及各自的表达水平. 结果表明,reAuMan5A和reAuMan5A^N3C3的最适温度Topt均为70 ℃,reAuMan5A^N3C3在60 ℃的半衰期t_1/2⁶⁰为38 min,较reAuMan5A（t_1/2⁶⁰=40 min）略有降低;在相同表达条件下,reAuMan5A^N3C3上清液的β-甘露聚糖酶活性为73.4 U/mL,较reAuMan5A 的52.8 U/mL提高了39.0%;纯化的reAuMan5A^N3C3酶比活性为182.7 U/mg protein,较reAuMan5A的126.3 U/mg protein提高了44.7%. 与reAuMan5A相比,reAuMan5A^N3C3对角豆胶的Km值下降不明显,Vmax值有显著提高.     

Multifactorial genetic models for quantitative traits in humans.

Quantitative traits measured in human families can be analyzed to partition the total population variance into genetic and environmental components, or to elucidate the genetic mechanism involved. We review the estimation of variance components directly from human pedigree data, or in the form of path coefficients from correlations between pairs of relatives. To elucidate genetic mechanisms, a mixed model that allows for segregation at a major locus, a polygenic effect and a sibling environmental correlation is described for nuclear families. In each case appropriate likelihoods are derived as a basis, using numerical maximum likelihood methods, for parameter estimation and hypothesis testing. A general model is then described that allows for several familial sources of environmental variation, assortative mating, and both major gene and polygenic effects; and an algorithm for calculating the likelihood of a pedigree under this model is indicated. Finally, some of the remaining problems in this area of biometric analysis are pointed out.     

Multifactorial inheritance with cultural transmission and assortative mating. II. a general model of combined polygenic and cultural inheritance.

A general linear model of combined polygenic-cultural inheritance is described. The model allows for phenotypic assortative mating, common environment, maternal and paternal effects, and genic-cultural correlation. General formulae for phenotypic correlation between family members in extended pedigrees are given for both primary and secondary assortative mating. A FORTRAN program BETA, available upon request, is used to provide maximum likelihood estimates of the parameters from reported correlations. American data about IQ and Burks' culture index are analyzed. Both cultural and genetic components of phenotypic variance are observed to make significant and substantial contributions to familial resemblance in IQ. The correlation between the environments of DZ twins is found to equal that of singleton sibs, not that of MZ twins. Burks' culture index is found to be an imperfect measure of midparent IQ rather than an index of home environment as previously assumed. Conditions under which the parameters of the model may be uniquely and precisely estimated are discussed. Interpretation of variance components in the presence of assortative mating and genic-cultural covariance is reviewed. A conservative, but robust, approach to the use of environmental indices is described.     

A rapid generalized least squares model for a genome-wide quantitative trait association analysis in families

Genome-wide association studies (GWAS) using family data involve association analyses between hundreds of thousands of markers and a trait for a large number of related individuals. The correlations among relatives bring statistical and computational challenges when performing these large-scale association analyses. Recently, several rapid methods accounting for both within- and between-family variation have been proposed. However, these techniques mostly model the phenotypic similarities in terms of genetic relatedness. The familial resemblances in many family-based studies such as twin studies are not only due to the genetic relatedness, but also derive from shared environmental effects and assortative mating. In this paper, we propose 2 generalized least squares (GLS) models for rapid association analysis of family-based GWAS, which accommodate both genetic and environmental contributions to familial resemblance. In our first model, we estimated the joint genetic and environmental variations. In our second model, we estimated the genetic and environmental components separately. Through simulation studies, we demonstrated that our proposed approaches are more powerful and computationally efficient than a number of existing methods are. We show that estimating the residual variance-covariance matrix in the GLS models without SNP effects does not lead to an appreciable bias in the p values as long as the SNP effect is small (i.e. accounting for no more than 1% of trait variance).     

晋西黄土区苹果树边材液流速率对环境驱动的响应

为明确环境因子对树木蒸腾过程的驱动机制,以晋西黄土残塬沟壑区的苹果树(红富士)为对象,利用热扩散式液流技术监测生长季苹果树树干液流的动态变化,并同步监测了气象和土壤水分等环境要素的季节动态.结果表明: 在众多环境因子中,太阳净辐射(R_n)、大气水分亏缺(VPD)与液流速率(J_s)间的相关性最强.在小时或日尺度,环境因子主成分分析中前3个主成分的累积方差贡献率均在86%以上.其中,第一主成分主要包含VPD、R_n等因子,方差贡献率达52%(小时尺度)和63%(日尺度)以上,可归为蒸发需求因子(EDI),是影响该地区果树树干液流的关键综合环境要素集;第二主成分主要包括土壤含水率(SWC)等因子,归为土壤水热供给因子;第三主成分主要包括风速等因子,归为大气水热散失动力因子.在小时或日尺度上,J_s对两种环境因子综合变量(EDI或潜在蒸发散ET₀)的响应都呈显著的指数增长关系,在小时尺度上,基于EDI模拟苹果J_s的指数模型精度更高(R²=0.72),在日尺度上,基于ET₀模拟苹果J_s的指数模型模拟精度更高(R²=0.88).研究结果对于明确苹果树水分传输对环境驱动的响应规律,根据气象要素估算苹果树蒸腾耗水量,并指导果园水分管理均具有重要意义.     

Causal analysis of the variability of IgA, IgG, and IgM immunoglobulin levels

The interindividual variability of IgA, IgG, and IgM immunoglobulin levels was studied using path analysis in a northeastern Brazilian sample (nuclear families) to determine the genetic and/or environmental causes of their variation. The path analysis model decomposes the phenotype into genetic causes (autosomal and X-chromosome-linked genes) and environmental causes. A significant familial aggregation, mainly resulting from autosomal components, was detected for the 3 immunoglobulin levels. The values of genetic heritability were h2 = 0.410 +/- 0.030 for IgA, h2 = 0.617 +/- 0.020 for IgG, and h2 = 0.540 +/- 0.023 for IgM, and the values for environmental-cultural heritability were c2 = 0.085 +/- 0.034 for IgA, c2 = 0.084 +/- 0.027 for IgG, and c2 = 0.023 + 0.023 for IgM. Our results did not show a heritable component resulting from X-chromosome-linked genes on IgM levels, as suggested by some studies (Wood et al. 1969; Grundbacher 1972; Purtilo and Sullivan 1979). Some additional results were that (1) age and IgA concentration were positively correlated, with IgA level increasing gradually from childhood to adulthood (p < 0.001); (2) sex and the age X sex interaction act on IgG concentration (p < 0.01); (3) age and IgM concentration are correlated (with children presenting lower levels than adults, especially in males, p < 0.01); and (4) a significant association exists between sex and IgM level (with females presenting higher levels than males, p < 0.001).     

Phenotypic, maximum genetic, and special environmental variability in prehistoric human populations

The phenotypic variance (V(P)) may be divided into the genetic variance (V(G)), the general environmental variance (V(Eg)), and the special environmental variance (V(Es)). The latter is estimated through repeatability calculation (b). This value is considered the upper limit of heritability and represents maximum genetic variance proportion (V(Gm) = V(G) + V(Eg)) in relation to V(P) (b = (V(G) + V(Eg))/V(P)). This process allows an improved determination of biological relationships among groups from estimators maximizing the genetic information of quantitative characters. Two hundred and thirty-seven individuals inhabiting the northern coast of Chile for 4,000 years were taken as a sample. Measurement was made of six metric characters at both sides of the cranium. Special environmental values (es) were obtained by regression. The difference between these values and the phenotypic values (p) consists in the genetic values plus the general environmental values (g + eg). A mean b value of 0.83 indicated that V(Es) represents 17% of V(P). The results showed: 1) high stability of the maximum genetic variance in time and space, 2) high correlation between the biological relationships model, the phenotypic model, and the maximum genetic model, and 3) random distribution of the nongenetic variation, as expected from the quantitative genetics theory. These results support the use of phenotypic data for the interpretation of the evolution history of prehistoric populations.     

Sex‐specific heritability of cell‐mediated immune response in the blue tit nestlings (Cyanistes caeruleus)

Here, we aimed at estimating sex‐specific heritabilities of cell‐mediated immune response (CMI) in the blue tit nestlings (Cyanistes caeruleus). To separate genetic and environmental components of the phenotypic variance in CMI (measured using phytohaemagglutinin assay), we performed a cross‐fostering experiment. Additionally, controlled environmental variation was introduced by enlarging some broods. Our analyses revealed a significant genetic component (as approximated by the nest‐of‐origin term) of the phenotypic variance in immune response. More importantly, these genetic effects differed between sexes and experimentally manipulated brood sizes, as indicated by significant genotype‐by‐sex and genotype‐by‐environment interactions. We discuss possible causes of such sexual dimorphism in gene expression and suggest that sex‐ and environment‐specific genetic interactions may contribute to the maintenance of genetic variability in traits related to immune functions.     

Soybean Mosaic Virus: Vector Specificity and Coat Protein Properties

Aphid transmission studies of two soybean mosaic virus isolates have shown that both isolates are transmitted by Myzus persicae. Only one of the isolates is transmitted by Rhopalosiphum maidis. The R. madis non-transmissible isolate could be transmitted from plants co-infected with the R. maidis transmissible isolate; aphid acquisition factor did not seem to mediate this transmission. The two isolates could be differentiated by enzyme-linked immunosorbent assay experiments, but peptide mapping experiments revealed few differences between the isolates.     

我国旱地春小麦产量及主要农艺指标的变异分析

采用4年、13个品种(系)、18个试点组成的全国旱地春小麦区域试验产量资料,通过联合方差分析和基因型及其与环境互作（GGE）双标图分析,研究了基因型、环境、基因型与环境互作效应（GEI）对产量变异的影响及品种的产量稳定性.结果表明：环境对产量变异的影响远大于基因型和GEI,环境引起的产量变异占87.5%～92.0%．互作因素中以地点×基因型的互作效应最大,基因型×年份的互作效应最小.我国旱地春小麦基因型多年多点的平均产量水平为2550 kg·hm^-2.产量三要素中,千粒重受环境的影响最小.影响产量变异的主要环境因子有：≥10 ℃年积温、生育期降雨量、平均气温、海拔、年降雨量和无霜期.产量与单位面积穗数（0.675^**）、穗粒数（0.581^**）、千粒重（0.456^**）呈极显著正相关,产量三要素间也呈正相关（0.244～0.480^**）,处于可同步提高范围.