Genetic variation and fitness in salmonids

Over the last quarter century, many studieshave attempted to clarify the relationshipbetween genetic variability and fitness, butfew of these have involved salmonid fishes. Examination of studies of salmonids revealsthat such a relationship varies both among andwithin species. A correlation between geneticvariability and fitness can be affected bygenetic background, environment, and age, andit also depends upon the genetic markers andphenotypes evaluated. The relationshipsbetween molecular genetic variation,quantitative genetic variation, and phenotypicvariation may be more relevant to conservationissues than those between genetic variation andaverage fitness or performance. Consequently,future work in salmonids should include moreintensive investigation of the correspondenceof molecular genetic variation within and amongpopulations to quantitative genetic andphenotypic variation for traits affectingfitness. In the absence of a more completeunderstanding of the relationship betweengenetic variation and fitness, maintenance ofgenetic and phenotypic variation within andamong conspecific populations should beconsidered a primary goal of conservingsalmonid fishes.     

Molecular processes in iron and zinc homeostasis and their modulation for biofortification in rice

More than a billion people suffer from iron or zinc deficiencies globally. Rice(Oryza sativa L.) iron and zinc biofortification; i.e., intrinsic iron and zinc enrichment of rice grains, is considered the most effective way to tackle these deficiencies. However, rice iron biofortification, by means of conventional breeding, proves difficult due to lack of sufficient genetic variation. Meanwhile,genetic engineering has led to a significant increase in the iron concentration along with zinc concentration in rice grains. The design of impactful genetic engineering biofortification strategies relies upon vast scientific knowledge of precise functions of different genes involved in iron and zinc uptake, translocation and storage. In this review, we present an overview of molecular processes controlling iron and zinc homeostasis in rice. Further,the genetic engineering approaches adopted so far to increase the iron and zinc concentrations in polished rice grains are discussed in detail, highlighting the limitations and/or success of individual strategies. Recent insight suggests that a few genetic engineering strategies are commonly utilized for elevating iron and zinc concentrations in different genetic backgrounds, and thus, it is of great importance to accumulate scientific evidence for diverse genetic engineering strategies to expand the pool of options for biofortifying farmer-preferred cultivars.     

《濒危野生动植物种国际贸易公约》与我国遗传资源管理对策

遗传资源是21世纪的战略资源之一, 是当代国际谈判中的热点问题。本文首先分析了《濒危野生动植物种国际贸易公约》(Convention on International Trade in Endangered Species of Wild Fauna and Flora, CITES)的运作机制、该公约涉及的遗传资源管理的条款及其对我国遗传资源管理的影响, 简要回顾了我国在CITES履约与遗传资源方面的立法和管理现状, 指出我国遗传资源管理领域亟待解决管理部门过多、立法不足、缺少明确的对外政策和国家战略、资源本底情况不详、产权划分不清、没有建立有利于野生动植物遗传资源保护与利用的经济调控机制等问题。最后, 我们提出了制定国家战略、建立遗传资源的协调管理机制、将遗传资源保护问题纳入相关法规、开展野生动植物遗传资源状况调查、建立有利于遗传资源保护的经济机制等解决对策。     

Genetic and linguistic coevolution in Northern Island Melanesia

Recent studies have detailed a remarkable degree of genetic and linguistic diversity in Northern Island Melanesia. Here we utilize that diversity to examine two models of genetic and linguistic coevolution. The first model predicts that genetic and linguistic correspondences formed following population splits and isolation at the time of early range expansions into the region. The second is analogous to the genetic model of isolation by distance, and it predicts that genetic and linguistic correspondences formed through continuing genetic and linguistic exchange between neighboring populations. We tested the predictions of the two models by comparing observed and simulated patterns of genetic variation, genetic and linguistic trees, and matrices of genetic, linguistic, and geographic distances. The data consist of 751 autosomal microsatellites and 108 structural linguistic features collected from 33 Northern Island Melanesian populations. The results of the tests indicate that linguistic and genetic exchange have erased any evidence of a splitting and isolation process that might have occurred early in the settlement history of the region. The correlation patterns are also inconsistent with the predictions of the isolation by distance coevolutionary process in the larger Northern Island Melanesian region, but there is strong evidence for the process in the rugged interior of the largest island in the region (New Britain). There we found some of the strongest recorded correlations between genetic, linguistic, and geographic distances. We also found that, throughout the region, linguistic features have generally been less likely to diffuse across population boundaries than genes. The results from our study, based on exceptionally fine-grained data, show that local genetic and linguistic exchange are likely to obscure evidence of the early history of a region, and that language barriers do not particularly hinder genetic exchange. In contrast, global patterns may emphasize more ancient demographic events, including population splits associated with the early colonization of major world regions.     

Rarity and genetic diversity in Indo-Pacific Acropora corals

Among various potential consequences of rarity is genetic erosion. Neutral genetic theory predicts that rare species will have lower genetic diversity than common species. To examine the association between genetic diversity and rarity, variation at eight DNA microsatellite markers was documented for 14 Acropora species that display different patterns of distribution and abundance in the Indo-Pacific Ocean. Our results show that the relationship between rarity and genetic diversity is not a positive linear association because, contrary to expectations, some rare species are genetically diverse and some populations of common species are genetically depleted. Our data suggest that inbreeding is the most likely mechanism of genetic depletion in both rare and common corals, and that hybridization is the most likely explanation for higher than expected levels of genetic diversity in rare species. A significant hypothesis generated from our study with direct conservation implications is that as a group, Acropora corals have lower genetic diversity at neutral microsatellite loci than may be expected from their taxonomic diversity, and this may suggest a heightened susceptibility to environmental change. This hypothesis requires validation based on genetic diversity estimates derived from a large portion of the genome.     

Stability and change in genetic and environmental influences on hand-grip strength in older male twins.

The aim of this study was to investigate aging-related changes in the contribution of genetic and environmental influences to hand-grip strength in late adulthood. Subjects in this study are 152 intact twin pairs (77 monozygotic and 75 dizygotic pairs) from the National Heart, Lung, and Blood Institute Twin Study assessed repeatedly for hand-grip strength at mean ages of 63 and 73 yr. Structural equation genetic modeling was used to investigate stability and change in the genetic and environmental components of variance of hand-grip strength in late adulthood. Average decline in strength over the 10 yr of follow-up was -1.05+/-6.8 (SD) kg and was highly significant (P = 0.003). The test-retest correlation between baseline and follow-up grip strength was 0.62 (P<0.001). Bivariate genetic modeling found significant genetic and shared environmental stability in hand-grip strength over the 10 yr of follow-up, with genetic and shared environmental influences accounting for 35 and 48%, respectively, of the test-retest phenotypic correlation. We conclude from these results that stability in hand-grip strength in late adulthood is due primarily to continuity of genetic and familial influences.     

Genetic similarity and hatching success in birds

The ecological correlates of fitness costs of genetic similarity in free-living, large populations of organisms are poorly understood. Using a dataset of genetic similarity as reflected by band-sharing coefficients of minisatellites, we show that bird species with higher genetic similarity experience elevated hatching failure of eggs, increasing by a factor of six across 99 species. Island distributions and cooperative breeding systems in particular were associated with elevated genetic similarity. These findings provide comparative evidence of detrimental fitness consequences of high genetic similarity across a wide range of species, and help to identify ecological factors potentially associated with increased risk of extinction.     

Languages, geography and HLA haplotypes in native American and Asian populations

A number of studies based on linguistic, dental and genetic data have proposed that the colonization of the New World took place in three separate waves of migration from North-East Asia. Recently, other studies have suggested that only one major migration occurred. It is the aim of this study to assess these opposing migration hypotheses using molecular-typed HLA class II alleles to compare the relationships between linguistic and genetic data in contemporary Native American populations. Our results suggest that gene flow and genetic drift have been important factors in shaping the genetic landscape of Native American populations. We report significant correlations between genetic and geographical distances in Native American and East Asian populations. In contrast, a less clear-cut relationship seems to exist between genetic distances and linguistic affiliation. In particular, the close genetic relationship of the neighbouring Na-Dene Athabaskans and Amerindian Salishans suggests that geography is the more important factor. Overall, our results are most congruent with the single migration model.     

Contrasting patterns of gene diversity between microsatellites and mitochondrial SNPs in farm and wild Atlantic salmon

Levels of genetic variability at 12 microsatellite loci and 19 single nucleotide polymorphisms in mitochondrial DNA were studied in four farm strains and four wild populations of Atlantic salmon. Within populations, the farm strains showed significantly lower allelic richness and expected heterozygosity than wild populations at the 12 microsatellite loci, but a significantly higher genetic variability with respect to observed number of haplotypes and haplotype diversity in mtDNA. Significant differences in allele- and haplotype-frequencies were observed between farm strains and wild populations, as well as between different farm strains and between different wild populations. The large genetic differentiation at mitochondrial DNA between wild populations (F_ST = 0.24), suggests that the farm strains attained a high mitochondrial genetic variability when created from different wild populations seven generations ago. A large proportion of this variability remains despite an expected lower effective population size for mitochondrial than nuclear DNA. This is best explained by the particular mating schemes in the breeding programmes, with 2–4 females per male. Our observations suggest that for some genetic polymorphisms farm populations might currently hold equal or higher genetic variability than wild populations, but lower overall genetic variability. In the short-term, genetic interactions between escaped farm salmon and wild salmon might increase genetic variability in wild populations, for some, but not most, genetic polymorphisms. In the long term, further losses of genetic variability in farm populations are expected for all genetic polymorphisms, and genetic variability in wild populations will be reduced if escapes of farm salmon continue.     

金黄地鼠与白化地鼠遗传生化基因位点概貌

目的建立金黄地鼠和白化地鼠遗传生化基因位点。方法选用小鼠和大鼠的遗传生化基因位点,采用蛋白质和同工酶醋酸纤维电泳的方法,对金黄地鼠和白化地鼠进行生化基因位点检测。结果建立了金黄地鼠和白化地鼠25个生化基因位点,分析金黄地鼠和白化地鼠遗传生化基因位点的多态性,为进一步研究金黄地鼠白化突变系的遗传机理奠定基础。结论金黄地鼠生化基因位点存在多态性,白化地鼠与金黄地鼠生化基因位点存在差异。     

Variation and constraint in plant evolution and development

The goal of this short review is to consider the interrelated phenomena of phenotypic variation and genetic constraint with respect to plant diversity. The unique aspects of plants, including sessile habit, modular growth and diverse developmental programs expressed at the phytomer level, merit a specific examination of the genetic basis of their phenotypic variation, and how they experience and escape genetic constraint. Numerous QTL studies with wild and domesticated plants reveal that most phenotypic traits are polygenic but vary in the number and effect of the loci contributing, from a few loci of large effects to many with small effects. Further, somatic mutations, developmental plasticity and epigenetic variation, especially gene methylation, can contribute to increases in phenotypic variation. The flip side of these processes, genetic constraint, can similarly be the result of many factors, including pleiotropy, canalization and genetic redundancy. Genetic constraint is not only a mechanism to prevent change, however, it can also serve to direct evolution along certain paths. Ultimately, genetic constraint often comes full circle and is released through events such as hybridization, genome duplication and epigenetic remodeling. We are just beginning to understand how these processes can operate simultaneously during the evolution of ecologically important traits in plants.     

Population structure and genetic diversity in four tropical tree species in Costa Rica

Despite intensified interest in conservation of tropical forests, knowledge of the population genetics of tropical forest trees remains limited. We used random amplified polymorphic DNA (RAPD) data to evaluate trends in genetic diversity and differentiation for four tropical tree species, Alchornea latifolia, Dendropanax arboreus, Inga thibaudiana and Protium glabrum . These species occur at contrasting population densities along an elevational gradient and we use RAPD and ecological data to examine natural levels of genetic diversity of each species, trends in genetic variability with population density and structure, genetic differentiation along the elevation gradient, and the relationship between genetic diversity and such factors as seed dispersal and pollination syndrome. At the distances we examined (plot distances ranging from 0.8 to 8.6 km) there was very little genetic structuring at any distance along the gradient. All four species exhibited levels of variation expected for spatial distribution, mating system and pollinator syndrome; greater than 96% of the genetic variation occurred within plots for Inga thibaudiana, Protium glabrum and Dendropanax arboreus. Alchornea latifolia only occurred in a single plot. The results of this study contribute to a growing database of genetic diversity data that can be utilized to make predictions about the effect of disturbance and subsequent reductions in population size on genetic variation and structure in tropical tree species.     

Landscape genetics in a changing world: disentangling historical and contemporary influences and inferring change

Landscape genetics seeks to determine the effect of landscape features on gene flow and genetic structure. Often, such analyses are intended to inform conservation and management. However, depending on the many factors that influence the time to reach equilibrium, genetic structure may more strongly represent past rather than contemporary landscapes. This well‐known lag between current demographic processes and population genetic structure often makes it challenging to interpret how contemporary landscapes and anthropogenic activity shape gene flow. Here, we review the theoretical framework for factors that influence time lags, summarize approaches to address this temporal disconnect in landscape genetic studies, and evaluate ways to make inferences about landscape change and its effects on species using genetic data alone or in combination with other data. Those approaches include comparing correlation of genetic structure with historical versus contemporary landscapes, using molecular markers with different rates of evolution, contrasting metrics of genetic structure and gene flow that reflect population genetic processes operating at different temporal scales, comparing historical and contemporary samples, combining genetic data with contemporary estimates of species distribution or movement, and controlling for phylogeographic history. We recommend using simulated data sets to explore time lags in genetic structure, and argue that time lags should be explicitly considered both when designing and interpreting landscape genetic studies. We conclude that the time lag problem can be exploited to strengthen inferences about recent landscape changes and to establish conservation baselines, particularly when genetic data are combined with other data.     

Streitkultur and the governance of genetic testing and insurance in Germany

Rapid developments in genetic testing have given rise to fundamental ethical, legal, and social questions that need to be dealt with in society. Results of genetic tests may be of interest to third parties such as private insurance companies, leading to fears of genetic discrimination. In Germany, the Government adopted the Genetic Diagnosis Act (Gendiagnostikgesetz, GenDG) in 2009 to protect people from, inter alia, genetic discrimination in obtaining life or health insurance. Given the sensitivity of the topic, this legislation was continually revised between 2001 and 2009. In this article, we reconstruct the process of formulating the GenDG with regard to genetics and insurance. The article begins with the parliamentary Enquete Commission in 2000 to develop a strategy and recommendations for the governance of genetic diagnostics, and analyzes how these recommendations were applied during the legislative process. We demonstrate that the legislative process of GenDG was largely determined by conventional methods of governance, rather than Streitkultur called for by the Enquete Commission in 2002. We conclude that though Streitkultur was defined as a mechanism to develop a robust approach to the governance of genetic diagnostics, it failed to influence a crucial element in genetic testing and insurance; namely, to fully protect insurees from genetic discrimination.     

Softwares and methods for estimating genetic ancestry in human populations

The estimation of genetic ancestry in human populations has important applications in medical genetic studies. Genetic ancestry is used to control for population stratification in genetic association studies, and is used to understand the genetic basis for ethnic differences in disease susceptibility. In this review, we present an overview of genetic ancestry estimation in human disease studies, followed by a review of popular softwares and methods used for this estimation.     

Societal problems in human and medical genetics

The applications of human and medical genetics raise many societal and ethical problems. This paper deals with a variety of such issues posed by current and future developments in genetic counseling, genetic screening, prenatal and predictive diagnosis, and gene therapy. The promise and problems of behavioral genetics are discussed. Problems of privacy, decision making, societal pressures, stigmatization, and informed consent to genetic study are raised. Use of genetic data by insurance companies or other public groups is discussed. The rapid unfolding of genetic information affecting human health and disease is producing difficult dilemmas. New problems are likely to surface, but human ingenuity and rationality is likely to find just and compassionate solutions in most settings.     

分子标记技术及其在植物遗传育种中的应用

本对遗传标记技术的发展历程作了简要的回顾。概述了目前常用的RFLP和RAPD等分子标记技术的基本原理和特点,及其在构建分子遗传图谱、品种间遗传关系分析、进行基因定位和测定遗传距离等遗传育种中的应用。     

Random and fixed effects in plant genetics

Summary A general model for any type of genetic entry is developed which takes into account both the factorial model of gene effects and the ancestral sources, whether inbred lines or outbred varieties, of the genes.Utilizing the model, various genetic designs of fixed entries are explored for the estimation of genetic effects and the testing of genetic hypotheses. These designs consisted of generation means — parents, crosses, various types of backcrosses, and so on — stemming from one or more pairs of parents, and of hybrid combinations from factorial mating designs. Limitations, from the standpoint of genetic effects that can be estimated and genetic hypotheses that can be tested, are developed in considerable detail.When entries from the factorial mating designs are considered to be random, attention is focused on the estimation of genetic variances, rather than effects, and on the concomitant changes in the tests of genetic hypotheses. While there is considerable improvement over fixed entries in the number of types of genetic variances that can be estimated, and of genetic hypotheses that can be tested, they are still very limited in contrast to what would be most desirable.Paper No. 6018 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, North Carolina. This investigation was supported in part by NIH Research Grant No. GM 11546 from the National Institute of General Medical Sciences.Preliminary: This paper was presented at the 7th International Biometric Conference. Since then it has come to various people's attention and I have been encouraged to give it a wider distribution. Except for editing, the paper is essentially as originally written.     

Genes as leaders and followers in evolution

A major question for the study of phenotypic evolution is whether intra- and interspecific diversity originates directly from genetic variation, or instead, as plastic responses to environmental influences initially, followed later by genetic change. In species with discrete alternative phenotypes, evolutionary sequences can be inferred from transitions between environmental and genetic phenotype control, and from losses of phenotypic alternatives. From the available evidence, sequences appear equally probable to start with genetic polymorphism as with polyphenism, with a possible dominance of one or the other for specific trait types. We argue in this review that to evaluate the prevalence of each route, an investigation of both genetic and environmental cues for phenotype determination in several related rather than in isolated species is required.     

The indication of genetic and environmental components in behaviour

The problem of genetic influences on behaviour was examined under the aspect of inter-specific differences, which are predomintantly genetic and are the basis of sociobiology. It was also examined under the aspect of intra-specific differences, notably the normal differences of behaviour which, like the sex differences, have a genetic basis. Further evidence for possible genetic influences on behaviour was given by considering limiting behaviours to which a limiting phenotype, usually pathological, corresponds. A comparison between genetic and non-genetic phenomena at the population level, shows a marked difference in the temporal variation of the two types of phenomena: those wich are under the control of gene frequencies tend to remain constant whereas those which are not under genetic control vary widely from one generation to the next, or from one year to the next. In Italy, in the period 1887–1980, it was observed that frequency of homicidal cases was extremely variable in time; whereas suicide in the same period was much less variable, and seemed correlated with genetic entities. It was reasoned that, although the study of human differences, including genetic ones, is amply desirable, the variations of extreme anomic behaviours are not demonstrably under genetic control; if a genetic component exists for such behaviours it must be quantitatively very small.